SlideShare a Scribd company logo

Javaserver Faces Introduction By Example Juneau Josh

D
degifhertay

Javaserver Faces Introduction By Example Juneau Josh Javaserver Faces Introduction By Example Juneau Josh Javaserver Faces Introduction By Example Juneau Josh

Education
1 of 86
Download to read offline
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
Javaserver Faces Introduction By Example Juneau Josh download https://ebookbell.com/product/javaserver-faces-introduction-by- example-juneau-josh-11704300 Explore and download more ebooks at ebookbell.com
Here are some recommended products that we believe you will be interested in. You can click the link to download. Javaserver Faces Introduction By Example 1st Edition Josh Juneau Auth https://ebookbell.com/product/javaserver-faces-introduction-by- example-1st-edition-josh-juneau-auth-4971844 Javaserver Faces Introduction By Example Josh Juneau https://ebookbell.com/product/javaserver-faces-introduction-by- example-josh-juneau-5052840 Javaserver Faces In Action 1st Edition Kito D Mann https://ebookbell.com/product/javaserver-faces-in-action-1st-edition- kito-d-mann-5470692 Javaserver Faces The Complete Reference Complete Reference Series 1st Edition Chris Schalk https://ebookbell.com/product/javaserver-faces-the-complete-reference- complete-reference-series-1st-edition-chris-schalk-1877086
Javaserver Faces 1st Hans Bergsten https://ebookbell.com/product/javaserver-faces-1st-hans- bergsten-917936 Core Javaserver Faces 2nd Ed David M Geary Cay S Horstmann https://ebookbell.com/product/core-javaserver-faces-2nd-ed-david-m- geary-cay-s-horstmann-4099476 Mastering Javaserver Faces 22 Illustrated Leonard Anghel https://ebookbell.com/product/mastering-javaserver- faces-22-illustrated-leonard-anghel-55587594 Mastering Javaserver Faces Bill Dudney Jonathan Lehr Bill Willis https://ebookbell.com/product/mastering-javaserver-faces-bill-dudney- jonathan-lehr-bill-willis-975282 Core Javaserver Faces Cay S Horstmann https://ebookbell.com/product/core-javaserver-faces-cay-s- horstmann-976172
Javaserver Faces Introduction By Example Juneau Josh
Javaserver Faces Introduction By Example Juneau Josh
For your convenience Apress has placed some of the front matter material after the index. Please use the Bookmarks and Contents at a Glance links to access them.
v Contents at a Glance About the Author ..............................................................................................................xvii Acknowledgments.............................................................................................................xix Chapter 1: Introduction to Servlets N ...................................................................................1 Chapter 2: JavaServer Pages N ..........................................................................................55 Chapter 3: The Basics of JavaServer Faces N ....................................................................99 Chapter 4: Facelets N ........................................................................................................163 Chapter 5: JavaServer Faces Standard Components N ....................................................205 Chapter 6: Advanced JavaServer Faces and Ajax N .........................................................261 Index.................................................................................................................................325
1 CHAPTER 1 Introduction to Servlets Java servlets were the first technology for producing dynamic Java web applications. Sun Microsystems released the first Java Servlet specification in 1997. Since then it has undergone tremendous change, making it more powerful and easing development more with each release. The 3.0 version was released as part of Java EE 6 in December 2009. Although not always used directly by Java web developers, servlets are at the base of all Java EE applications. Many developers use servlet frameworks such as Java Server Pages (JSP) and Java Server Faces (JSF), both of those technologies compile pages into Java servlets behind the scenes via the servlet container. That said, a fundamental knowledge of Java servlet technology is very useful for any Java web developer. Servlets are Java classes that conform to the Java Servlet API, which allows a Java class to respond to requests. Although servlets can respond to any type of request, they are most commonly written to respond to HTTP requests. A servlet must be deployed to a Java servlet container in order to become usable. The Servlet API provides a number of objects that are used to enable the functionality of a servlet within a web container. Such objects include the request and response objects, pageContext, and a great deal of others, and when these objects are used properly, they enable a Java servlet to perform just about any task a web-based application needs to perform. As mentioned, servlets can produce not only static content but also dynamic content. Since a servlet is written in Java, any valid Java code can be used within the body of the servlet class. This empowers Java servlets and allows them to interact with other Java classes, the web container, the underlying file server, and much more. This chapter will get you started developing and deploying servlets, and provide you with foundational knowledge to move forward with other servlet-based web frameworks In this chapter, you will learn how to install Oracle’s GlassFish application server, a robust servlet container, which will enable you to deploy sophisticated Java enterprise applications. You will be taught the basics of developing servlets, how to use them with client web sessions, and how to link a servlet to another application. All the while, you will learn to use standards from the latest release of the Java Servlet API (3.2), which modernizes servlet development and makes it much easier and more productive than in years past. Note N You can run the examples within this chapter by deploying the JSFByExample.war file (contained in the sources) to a local Java EE application server container such as GlassFish v4.x. You can also set up the NetBeans 8.x project entitled JSFByExample that is contained in the sources, build it, and deploy to GlassFish v4.x. Otherwise, you can run the examples in Chapter 1 stand-alone using the instructions provided in the section “Packaging, Compiling, and Deploying a Servlet”. If you deploy the JSFByExample.war file to a Java EE application server container, you can visit the following URL to load the examples for this chapter: http://localhost:8080/JSFByExample/faces/chapter01/index.xhtml.
CHAPTER 1 N INTRODUCTION TO SERVLETS 2 Setting Up a Java Enterprise Environment You’ll need an environment in which to experiment with servlets, and then later with JavaServer Faces. Oracle’s GlassFish application server is a good choice, as it is the Java EE 7 Reference Impementation. It’s easy to set up, and the following example will get you started and ready to run all the subsequent examples in the book. Example To get started, ownload and install Oracle’s GlassFish application server from the GlassFish web site. The version used for this book is the open source edition, release 4.1, and it can be downloaded from http://glassfish.java.net/ in the “Download” section. Select the .zip or .tar.gz download format, and decompress the downloaded files within a directory on your workstation. I will refer to that directory as /JAVA_DEV/GlassFish. The GlassFish distribution comes prepackaged with a domain so that developers can get up and running quickly. Once the .zip file has been unpacked, you can start the domain by opening a command prompt or terminal and starting GlassFish using the following statement: /PATH_TO_GLASSFISH /GlassFish/bin/asadmin start-domain domain1 The domain will start, and it will be ready for use. You will see output from the server that looks similar to the following: Waiting for domain1 to start ............ Successfully started the domain : domain1 domain Location: /PATH_TO_GLASSFISH/glassfish/domains/domain1 Log File: /PATH_TO_GLASSFISH/glassfish/domains/domain1/logs/server.log Admin Port: 4848 Command start-domain executed successfully. Explanation The development of Java EE applications begins with a Java EE–compliant application server. A Java EE–compliant server contains all the essential components to provide a robust environment for deploying and hosting enterprise Java applications. The GlassFish application server is the industry standard for Java EE 7. As of GlassFish 4.0, there is only an open sourced distribution of the server available, meaning that it is not possible to purchase Oracle support for GlassFish. However, in a production environment, you may want to consider purchasing GlassFish 4.x support from a third-party organization so that technical support will be available if needed. An alternative is to utilize a commercially supported server that is Java EE 7 compliant, such as Oracle WebLogic 12.1.x. Installing GlassFish is easy. It consists of downloading an archive and uncompressing it on your development machine. Once you’ve completed this, the application server will make use of your locally installed Java development kit (JDK) when it is started. JDK 8 is supported for use with GlassFish as of release 4.1. For GlassFish 4.0, please use JDK 7. Once the server starts, you can open a browser and go to http://localhost:4848 to gain access to the GlassFish administrative console. Most Java EE developers who deploy on GlassFish use the administrative console often. The administrative console provides developers with the tools needed to deploy web applications, register databases with Java Naming and Directory Interface (JNDI), set up security realms for a domain, and do much more. You should take some time to become familiar with the administrative console because the more you know about it, the easier it will be to maintain your Java EE environment. Installing the GlassFish application server is the first step toward developing Java applications for the enterprise. While other applications servers such as JBoss WildFly, Apache TomEE, and WebLogic are very well adopted, GlassFish offers developers a solid environment that is suitable for production use and easy to learn. It also has the bonus of being an open source application server and the reference implementation for Java EE 7.
CHAPTER 1 N INTRODUCTION TO SERVLETS 3 Developing Your First Servlet Web applications are based upon a series of web views or pages. There is often a requirement to develop a view that has the ability to include content that may change at any given time. For instance, you may be developing a view that contains stock data, and you may wish to have that data updated often. Servlets provide the ability to produce dynamic content, allowing server-side computations and processes to update the data in the servlet at will. Example Develop a Java servlet class, and compile it to run within a Java servlet container. In this example, a simple servlet is created that will display some dynamic content to the web page. The The following code is the servlet code that contains the functionality for the servlet:package org.javaserverfaces.chapter01; import java.io.IOException; import java.io.PrintWriter; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; /** * Simple Dynamic Servlet * @author juneau */ public class SimpleServlet extends HttpServlet { /** * Processes requests for both HTTP * <code>GET</code> and * <code>POST</code> methods. * * @param request servlet request * @param response servlet response * @throws ServletException if a servlet-specific error occurs * @throws IOException if an I/O error occurs */ protected void processRequest(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.setContentType("text/html;charset=UTF-8"); PrintWriter out = response.getWriter(); try { /* * TODO output your page here. You may use following sample code. */ out.println("<html>"); out.println("<head>"); out.println("<title>Servlet SimpleServlet</title>"); out.println("</head>"); out.println("<body>"); out.println("<h2>Servlet SimpleServlet at " + request.getContextPath() + "</h2>"); out.println("<br/>Welcome to JavaServer Faces: Introduction By Example!");
CHAPTER 1 N INTRODUCTION TO SERVLETS 4 out.println("</body>"); out.println("</html>"); } finally { out.close(); } } // <editor-fold defaultstate="collapsed" desc="HttpServlet methods. Click on the + sign on the left to edit the code."> /** * Handles the HTTP * <code>GET</code> method. * * @param request servlet request * @param response servlet response * @throws ServletException if a servlet-specific error occurs * @throws IOException if an I/O error occurs */ @Override protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { processRequest(request, response); } /** * Handles the HTTP * <code>POST</code> method. * * @param request servlet request * @param response servlet response * @throws ServletException if a servlet-specific error occurs * @throws IOException if an I/O error occurs */ @Override protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { processRequest(request, response); } /** * Returns a short description of the servlet. * * @return a String containing servlet description */ @Override public String getServletInfo() { return "Short description"; }// </editor-fold> }
CHAPTER 1 N INTRODUCTION TO SERVLETS 5 The following code is the web deployment descriptor. This file is required for application deployment to a servlet container. It contains the servlet configuration and mapping that maps the servlet to a URL. Later in this chapter, will learn how to omit the servlet configuration and mapping from the web.xml file to make servlet development, deployment, and maintenance easier. <?xml version="1.0"?> <web-app xmlns="http://java.sun.com/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" version="3.0"> <servlet> <servlet-name>SimpleServlet</servlet-name> <servlet-class>org.javaeeexamples.chapter1.example01_02.SimpleServlet</servlet-class> </servlet> <servlet-mapping> <servlet-name>SimpleServlet</servlet-name> <url-pattern>/SimpleServlet</url-pattern> </servlet-mapping> <welcome-file-list> <welcome-file> /SimpleServlet </welcome-file> </welcome-file-list> </web-app> Note N Many web applications use a page named index.html or index.xhtml as their welcome file. There is nothing wrong with doing that, and as a matter of fact, it is the correct thing to do. The use of /SimpleServlet as the welcome file in this example is to make it easier to follow for demonstration purposes. To compile the Java servlet, use the javac command-line utility. The following line was excerpted from the command line, and it compiles the SimpleServlet.java file into a class file. First, traverse into the directory containing the SimpleServlet.java file; then, execute the following: javac -cp /JAVA_DEV/GlassFish/glassfish/modules/javax.servlet-api.jar SimpleServlet.java Once the servlet code has been compiled into a Java class file, it is ready to package for deployment. Note N You may want to consider installing a Java integrated development environment (IDE) to increase your develop- ment productivity. There are several very good IDEs available to developers, so be sure to choose one that contains the features you find most important and useful for development. As the author of this book on Java EE 7, I recommend installing NetBeans 8.x or newer for development. NetBeans is an open source IDE that is maintained by Oracle, and it includes support for all the cutting-edge features that the Java industry has to offer, including EJB development with Java EE 7, JavaFX 8 support, and more.
CHAPTER 1 N INTRODUCTION TO SERVLETS 6 Explanation Java servlets provide developers with the flexibility to design applications using a request-response programming model. Servlets play a key role in the development of service-oriented and web application development on the Java platform. Different types of servlets can be created, and each of them is geared toward providing different functionality. The first type is the GenericServlet, which provides services and functionality. The second type, HttpServlet, is a subclass of GenericServlet, and servlets of this type provide functionality and a response that uses HTTP. The solution to this example demonstrates the latter type of servlet because it displays a result for the user to see within a web browser. Servlets conform to a life cycle for processing requests and posting results. First, the Java servlet container calls the servlet’s constructor. The constructor of every servlet must take no arguments. Next, the container calls the servlet init method, which is responsible for initializing the servlet. Once the servlet has been initialized, it is ready for use. At that point, the servlet can begin processing. Each servlet contains a service method, which handles the requests being made and dispatches them to the appropriate methods for request handling. Implementing the service method is optional. Finally, the container calls the servlet’s destroy method, which takes care of finalizing the servlet and taking it out of service. Every servlet class must implement the javax.servlet.Servlet interface or extend another class that does. In the solution to this example, the servlet named SimpleServlet extends the HttpServlet class, which provides methods for handling HTTP processes. In this scenario, a browser client request is sent from the container to the servlet; then the servlet service method dispatches the HttpServletRequest object to the appropriate method provided by HttpServlet. Namely, the HttpServlet class provides the doGet, doPut, doPost, and doDelete methods for working with an HTTP request. The HttpServlet class is abstract, so it must be subclassed, and then an implementation can be provided for its methods. In the solution to this example, the doGet method is implemented, and the responsibility of processing is passed to the processRequest method, which writes a response to the browser using the PrintWriter. Table 1-1 describes each of the methods available to an HttpServlet. Table 1-1. HttpServlet Methods Method Name Description doGet Used to process HTTP GET requests. Input sent to the servlet must be included in the URL address. For example: ?myName=Josh&myBook=JSF. doPost Used to process HTTP POST requests. Input can be sent to the servlet within HTML form fields. doPut Used to process HTTP PUT requests. doDelete Used to process HTTP DELETE requests. doHead Used to process HTTP HEAD requests. doOptions Called by the container to allow OPTIONS request handling. doTrace Called by the container to handle TRACE requests. getLastModified Returns the time that the HttpServletRequest object was last modified. init Initializes the servlet. destroy Finalizes the servlet. getServletInfo Provides information regarding the servlet.
CHAPTER 1 N INTRODUCTION TO SERVLETS 7 A servlet generally performs some processing within the implementation of its methods and then returns a response to the client. The HttpServletRequest object can be used to process arguments that are sent via the request. For instance, if an HTML form contains some input fields that are sent to the server, those fields would be contained within the HttpServletRequest object. The HttpServletResponse object is used to send responses to the client browser. Both the doGet and doPost methods within a servlet accept the same arguments, namely, the HttpServletRequest and HttpServletResponse objects. Note N The doGet method is used to intercept HTTP GET requests, and doPost is used to intercept HTTP POST requests. Generally, the doGet method is used to prepare a request before displaying for a client, and the doPost method is used to process a request and gather information from an HTML form. In the solution to this example, both the doGet and doPost methods pass the HttpServletRequest and HttpServletResponse objects to the processRequest method for further processing. The HttpServletResponse object is used to set the content type of the response and to obtain a handle on the PrintWriter object in the processRequest method. The following lines of code show how this is done, assuming that the identifier referencing the HttpServletResponse object is response: response.setContentType("text/html;charset=UTF-8"); PrintWriter out = response.getWriter(); A GenericServlet can be used for providing services to web applications. This type of servlet is oftentimes used for logging events because it implements the log method. A GenericServlet implements both the Servlet and ServletConfig interfaces, and to write a generic servlet, only the service method must be overridden. How to Package, Compile, and Deploy a Servlet Once a servlet has been developed (and compiled), it needs to be deployed to a servlet container before it can be used. After deployment to the server, the servlet needs to be mapped to a URL for invocation. Example Compile the sources, set up a deployable application, and copy the contents into the GlassFish deployment directory. From the command line, use the javac command to compile the sources. javac -cp /PATH_TO_GLASSFISH/GlassFish/glassfish/modules/javax.servlet-api.jar SimpleServlet.java After the class has been compiled, deploy it along with the web.xml deployment descriptor, conforming to the appropriate directory structure. In web.xml, declare the servlet, and map it to a URL using the following format: <servlet> <servlet-name>SimpleServlet</servlet-name> <servlet-class>org.javaserverfaces.chapter01.SimpleServlet</servlet-class> </servlet> </servlet-mapping> <servlet-mapping> <servlet-name>SimpleServlet</servlet-name> <url-pattern>/SimpleServlet</url-pattern> </servlet-mapping>
CHAPTER 1 N INTRODUCTION TO SERVLETS 8 QUICK START FOR DEPLOYING WITHOUT AN IDE To quickly get started with packaging, compiling, and deploying the example application for the servlet examples in this chapter on GlassFish or other servlet containers such as Apache Tomcat without an IDE, follow these steps: 1. Create a single application named SimpleServlet by making a directory named SimpleServlet. 2. Create a directory at the root of the application, and name it WEB-INF. Create an XML file in the new WEB-INF directory, and name it web.xml. In the web.xml, add the following markup: <?xml version="1.0" encoding="UTF-8"?> <web-app version="3.1" xmlns="http://xmlns.jcp.org/xml/ns/javaee" xmlns:xsi=" http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://xmlns.jcp.org/ xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd"> <servlet> <servlet-name>SimpleServlet</servlet-name> <servlet-class>org.javaserverfaces.chapter01.SimpleServlet</servlet-class> </servlet> <servlet-mapping> <servlet-name>SimpleServlet</servlet-name> <url-pattern>/SimpleServlet</url-pattern> </servlet-mapping> <session-config> <session-timeout> 30 </session-timeout> </session-config> </web-app> 3. Create “classes”, and “lib” drectories inside the directory that was created in step 2. Drag the Chapter 1 sources into the WEB-INF/classes directory. 4. Set your CLASSSPATH to include any necessary JAR files. For this chapter, the JavaMail API JAR (mail.jar) is required. Place it into the WEB-INF/lib directory and set your CLASSPATH accordingly. 5. At the command prompt, change directories so that you are within the “classes” directory that was created in Step 3. Compile each class within the org.javaserverfaces. chapter01 directory with the following command: javac orgjavaserverfaceschapter01*.java 6. Copy your SimpleServlet application into the /JAVA_DEV/GlassFish/glassfish/domains/ domain1/autodeploy directory for GlassFish, or the /Tomcat/webapps directory for Tomcat. Test the application by launching a browser and going to http://localhost:8080/SimpleServlet/servlet_ name, where servlet_name corresponds to the servlet name in each example. If using Tomcat, you may need to restart the server in order for the application to deploy.
CHAPTER 1 N INTRODUCTION TO SERVLETS 9 Explanation To compile the sources, you can use your favorite Java IDE such as NetBeans or Eclipse, or you can use the command line. For the purposes of this example, I will use the command line. Note that in many of the remaining examples for this book, the NetBeans IDE is used. If you’re using the command line, you must ensure you are using the javac command that is associated with the same Java release that you will be using to run your servlet container. In this example we will assume that GlassFish 4.1 is being used with JDK 7, and therefore assume that the location of the Java SE 7 installation is at the following path: /Library/Java/JavaVirtualMachines/1.7.0.jdk/Contents/Home This path may differ in your environment if you are using a different operating system and/or installation location. To ensure you are using the Java runtime that is located at this path, set the JAVA_HOME environment variable equal to this path. On OS X and *nix operating systems, you can set the environment variable by opening the terminal and typing the following: export JAVA_HOME=/Library/Java/JavaVirtualMachines/1.7.0.jdk/Contents/Home If you are using Windows, use the SET command within the command line to set up the JAVA_HOME environment variable. set JAVA_HOME=C:your-java-se-path Next, compile your Java servlet sources, and be sure to include the javax.servlet-api.jar file that is packaged with your servlet container (use servlet-api.jar for Tomcat) in your CLASSPATH. You can set the CLASSPATH by using the –cp flag of the javac command. The following command should be executed at the command line from within the same directory that contains the sources. In this case, the source file is named SimpleServlet.java. javac -cp /path_to_jar/javax.servlet-api.jar SimpleServlet.java Next, package your application by creating a directory and naming it after your application. In this case, create a directory and name it SimpleServlet. Within that directory, create another directory named WEB-INF. Traverse into the WEB-INF directory, and create another directory named classes. Lastly, create directories within the classes directory in order to replicate your Java servlet package structure. For this example, the SimpleServlet.java class resides within the Java package org.javaserverfaces.chapter01, so create a directory for each of those packages within the classes directory. Create another directory within WEB-INF and name it lib; any JAR files containing external libraries should be placed within the lib directory. In the end, your directory structure should resemble the following: SimpleServlet |_WEB-INF |_classes |_org |_javaserverfaces |_chapter01 |_lib Place your web.xml deployment descriptor within the WEB-INF directory, and place the compiled SimpleServlet.class file within the chapter01 directory. The entire contents of the SimpleServlet directory can now be copied within the deployment directory for your application server container to deploy the application. Restart the application server if using Tomcat, and visit the URL http://localhost:8080/SimpleServlet/ SimpleServlet to see the servlet in action.
CHAPTER 1 N INTRODUCTION TO SERVLETS 10 Registering Servlets Without WEB-XML Registering servlets in the web.xml file is cumbersome. With the later releases of the Servlet specification, it is possible to deploy servlets without the requirement for a web.xml file. In this section, we will take a look at how to register servlets without the web.xml requirement. Example Use the @WebServlet annotation to register the servlet, and omit the web.xml registration. This will alleviate the need to modify the web.xml file each time a servlet is added to your application. The following adaptation of the SimpleServlet class that was used in the previous example includes the @WebServlet annotation and demonstrates its use: package org.javaserverfaces.chapter01; import java.io.IOException; import java.io.PrintWriter; import javax.servlet.ServletException; import javax.servlet.annotation.WebServlet; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; /** * Registering Servlets without WEB-XML * @author juneau */ @WebServlet(name = "SimpleServletNoDescriptor", urlPatterns = {"/SimpleServletNoDescriptor"}) public class SimpleServletNoDescriptor extends HttpServlet { /** * Processes requests for both HTTP * <code>GET</code> and * <code>POST</code> methods. * * @param request servlet request * @param response servlet response * @throws ServletException if a servlet-specific error occurs * @throws IOException if an I/O error occurs */ protected void processRequest(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.setContentType("text/html;charset=UTF-8"); PrintWriter out = response.getWriter(); try { /* * TODO output your page here. You may use following sample code. */ out.println("<html>"); out.println("<head>"); out.println("<title>Servlet SimpleServlet</title>");
CHAPTER 1 N INTRODUCTION TO SERVLETS 11 out.println("</head>"); out.println("<body>"); out.println("<h2>Servlet SimpleServlet at " + request.getContextPath() + "</h2>"); out.println("<br/>Look ma, no WEB-XML!"); out.println("</body>"); out.println("</html>"); } finally { out.close(); } } /** * Handles the HTTP <code>GET</code> method. * * @param request servlet request * @param response servlet response * @throws ServletException if a servlet-specific error occurs * @throws IOException if an I/O error occurs */ @Override protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { processRequest(request, response); } /** * Handles the HTTP <code>POST</code> method. * * @param request servlet request * @param response servlet response * @throws ServletException if a servlet-specific error occurs * @throws IOException if an I/O error occurs */ @Override protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { processRequest(request, response); } } In the end, the servlet will be accessible via a URL in the same way that it would if the servlet were registered within web.xml. Explanation There are a couple of ways to register servlets with a web container. The first way is to register them using the web.xml deployment descriptor, as demonstrated earlier in the chapter. The second way to register them is to use the @WebServlet annotation. The Servlet 3.0 API introduced the @WebServlet annotation, which provides an easier technique to use for mapping a servlet to a URL. The @WebServlet annotation is placed before the declaration of a class, and it accepts the elements listed in Table 1-2.
CHAPTER 1 N INTRODUCTION TO SERVLETS 12 In the solution to this example, the @WebServlet annotation maps the servlet class named SimpleServletNoDescriptor to the URL pattern of /SimpleServletNoDescriptor, and it also names the servlet SimpleServletNoDescriptor. @WebServlet(name="SimpleServletNoDescriptor", urlPatterns={"/SimpleServletNoDescriptor"}) The new @WebServlet can be used rather than altering the web.xml file to register each servlet in an application. This provides ease of development and manageability. However, in some cases, it may make sense to continue using the deployment descriptor for servlet registration, such as if you do not want to recompile sources when a URL pattern changes. If you look at the web.xml file used earlier, you can see the following lines of XML, which map the servlet to a given URL and provide a name for the servlet. These lines of XML perform essentially the same function as the @WebServlet annotation in this example. <servlet> <servlet-name>SimpleServletNoDescriptor</servlet-name> <servlet-class>org.javaserverfaces.chapter01.SimpleServletNoDescriptor</servlet-class> </servlet> <servlet-mapping> <servlet-name>SimpleServletNoDescriptor</servlet-name> <url-pattern>/SimpleServletNoDescriptor</url-pattern> </servlet-mapping> Displaying Dynamic Content with a Servlet As mentioned previously in the chapter, it sometimes makes sense to deliver dynamic content (content that changes frequently), rather than serving static content that never changes. In this example, we will take a look at how to develop a servlet that has the ability to display dynamic content. Table 1-2. @WebServlet Annotation Elements Element Description description Description of the servlet displayName The display name of the servlet initParams Accepts list of @WebInitParam annotations largeIcon The large icon of the servlet loadOnStartup Load on start-up order of the servlet name Servlet name smallIcon The small icon of the servlet urlPatterns URL patterns that invoke the servlet
CHAPTER 1 N INTRODUCTION TO SERVLETS 13 Example Define a field within your servlet to contain the dynamic content that is to be displayed. Post the dynamic content on the page by appending the field containing it using the PrintWriter println method. The following example servlet declares a Date field and updates it with the current Date each time the page is loaded: package org.javaserverfaces.chapter01; import java.io.IOException; import java.io.PrintWriter; import java.util.Date; import javax.servlet.ServletException; import javax.servlet.annotation.WebServlet; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; /** * Displaying Dynamic Content with a Servlet * * @author juneau */ @WebServlet(name = "CurrentDateAndTime", urlPatterns = {"/CurrentDateAndTime"}) public class CurrentDateAndTime extends HttpServlet { /** * Processes requests for both HTTP <code>GET</code> and <code>POST</code> * methods. * * @param request servlet request * @param response servlet response * @throws ServletException if a servlet-specific error occurs * @throws IOException if an I/O error occurs */ protected void processRequest(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.setContentType("text/html;charset=UTF-8"); PrintWriter out = response.getWriter(); try { out.println("<html>"); out.println("<head>"); out.println("<title>Servlet CurrentDateAndTime</title>"); out.println("</head>"); out.println("<body>"); out.println("<h1>Servlet CurrentDateAndTime at " + request.getContextPath() + "</h1>"); out.println("<br/>"); Date currDateAndTime = new Date(); out.println("The current date and time is: " + currDateAndTime);
CHAPTER 1 N INTRODUCTION TO SERVLETS 14 out.println("</body>"); out.println("</html>"); } finally { out.close(); } } /** * Handles the HTTP <code>GET</code> method. * * @param request servlet request * @param response servlet response * @throws ServletException if a servlet-specific error occurs * @throws IOException if an I/O error occurs */ @Override protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { processRequest(request, response); } /** * Handles the HTTP <code>POST</code> method. * * @param request servlet request * @param response servlet response * @throws ServletException if a servlet-specific error occurs * @throws IOException if an I/O error occurs */ @Override protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { processRequest(request, response); } } The resulting output from this servlet will be the current date and time. Explanation One of the reasons why Java servlets are so useful is because they allow dynamic content to be displayed on a web page. The content can be taken from the server itself, a database, another web site, or many other web-accessible resources. Servlets are not static web pages; they are dynamic, and that is arguably their biggest strength. In the solution to this example, a servlet is used to display the current time and date on the server. When the servlet is processed, the doGet method is called, which subsequently makes a call to the processRequest method, passing the request and response objects. Therefore, the processRequest method is where the bulk of the work occurs. The processRequest method creates a PrintWriter by calling the response.getWriter method, and the PrintWriter is used to display content on the resulting web page. Next, the current date and time are obtained from the server by creating a new Date and assigning it to the currDateAndTime field. Lastly, the processRequest method sends the web content through the out.println method, and the contents of the currDateAndTime field are concatenated to a String and sent to out.println as well. Each time the servlet is processed, it will display the current date and time at the time in which the servlet is invoked because a new Date is created with each request.
CHAPTER 1 N INTRODUCTION TO SERVLETS 15 This example just scratches the surface of what is possible with a Java servlet. Although displaying the current date and time is trivial, you could alter that logic to display the contents of any field contained within the servlet. Whether it be an int field that displays a calculation that was performed by the servlet container or a String field containing some information, the possibilities are endless. Handling Requests and Responses Most applications allow forms that accept input, and then produce a response. This is one of the main components of an HTTP application, and servlets are ideal for handling a request-response lifecycle. It can also be useful to develop forms in HTML, and have the form submitted to a processing engine, such as a servlet. Example To see a request-response example in action, create a standard HTML-based web form, and when the submit button is clicked, invoke a servlet to process the end-user input and post a response. To examine this technique, you will see two different pieces of code. The following code is HTML that is used to generate the input form. Pay particular attention to the <form> and <input> tags. You will see that the form’s action parameter lists a servlet name, MathServlet. <html> <head> <title>Simple Math Servlet</title> </head> <body> <h1>This is a simple Math Servlet</h1> <form method="POST" action="MathServlet"> <label for="numa">Enter Number A: </label> <input type="text" id="numa" name="numa"/><br><br> <label for="numb">Enter Number B: </label> <input type="text" id="numb" name="numb"/><br/><br/> <input type="submit" value="Submit Form"/> <input type="reset" value="Reset Form"/> </form> </body> </html> Next, take a look at the following code for a servlet named MathServlet. This is the Java code that receives the input from the HTML code listed earlier, processes it accordingly, and posts a response. package org.javaserverfaces.chapter01; import java.io.IOException; import java.io.PrintWriter; import java.util.Date; import javax.servlet.*; import javax.servlet.annotation.WebServlet; import javax.servlet.http.*;
CHAPTER 1 N INTRODUCTION TO SERVLETS 16 /** * Handling Requests and Responses */ // Uncomment the following line to run example stand-alone //@WebServlet(name="SessionServlet", urlPatterns={"/MathServlet"}) // The following will allow the example to run within the context of the JSFByExample example // enterprise application (JSFByExample.war distro or Netbeans Project) @WebServlet(name = "MathServlet", urlPatterns = {"/chapter01/MathServlet"}) public class MathServlet extends HttpServlet { public void doPost(HttpServletRequest req, HttpServletResponse res) throws IOException, ServletException { res.setContentType("text/html"); // Store the input parameter values into Strings String numA = req.getParameter("numa"); String numB = req.getParameter("numb"); PrintWriter out = res.getWriter(); out.println("<html><head>"); out.println("<title>Test Math Servlet</title>"); out.println("t<style>body { font-family: 'Lucida Grande', " + "'Lucida Sans Unicode';font-size: 13px; }</style>"); out.println("</head>"); out.println("<body>"); try { int solution = Integer.valueOf(numA) + Integer.valueOf(numB); /* * Display some response to the user */ out.println("<p>Solution: " + numA + " + " + numB + " = " + solution + "</p>"); } catch (java.lang.NumberFormatException ex) { // Display error if an exception is raised out.println("<p>Please use numbers only...try again.</p>"); } out.println("</body></html>"); out.close(); } }
CHAPTER 1 N INTRODUCTION TO SERVLETS 17 Note N To run the example, deploy the JSFByExample application to your application server container, and then enter the following address into your browser: http://localhost:8080/JSFByExample/chapter01/math.html. This assumes you are using default port numbers for your application server installation. If using the NetBeans project that was packaged with the sources, you do not need to worry about copying the code as everything is pre-configured. Explanation Servlets make it easy to create web applications that adhere to a request and response life cycle. They have the ability to provide HTTP responses and also process business logic within the same body of code. The ability to process business logic makes servlets much more powerful than standard HTML code. The solution to this example demonstrates a standard servlet structure for processing requests and sending responses. An HTML web form contains parameters that are sent to a servlet. The servlet then processes those parameters in some fashion and publishes a response that can be seen by the client. In the case of an HttpServlet object, the client is a web browser, and the response is a web page. Values can be obtained from an HTML form by using HTML <input> tags embedded within an HTML <form>. In the solution to this example, two values are accepted as input, and they are referenced by their id attributes as numa and numb. There are two more <input> tags within the form; one of them is used to submit the values to the form action, and the other is used to reset the form fields to blank. The form action is the name of the servlet that the form values will be passed to as parameters. In this case, the action is set to MathServlet. The <form> tag also accepts a form-processing method, either GET or POST. In the example, the POST method is used because form data is being sent to the action; in this case, data is being sent to MathServlet. You could, of course, create an HTML form as detailed as you would like and then have that data sent to any servlet in the same manner. This example is relatively basic; it serves to give you an understanding of how the processing is performed. The <form> action attribute states that the MathServlet should be used to process the values that are contained within the form. The MathServlet name is mapped back to the MathServlet class via the web.xml deployment descriptor or the @WebServlet annotation. Looking at the MathServlet code, you can see that a doPost method is implemented to handle the processing of the POST form values. The doPost method accepts HttpServletRequest and HttpServletResponse objects as arguments. The values contained with the HTML form are embodied within the HttpServletRequest object. To obtain those values, call the request object’s getParameter method, passing the id of the input parameter you want to obtain. In this example, those values are obtained and stored within local String fields. String numA = req.getParameter("numa"); String numB = req.getParameter("numb"); Once the values are obtained, they can be processed as needed. In this case, those String values are converted into int values, and then they are added together to generate a sum and stored into an int field. That field is then presented as a response on a resulting web page. int solution = Integer.valueOf(numA) + Integer.valueOf(numB); As mentioned, the HTML form could be much more complex, containing any number of <input> fields. Likewise, the servlet could perform more complex processing of those field values. This example is merely the tip of the iceberg, and the possibilities are without bounds. Servlet-based web frameworks such as Java Server Pages and Java Server Faces hide many of the complexities of passing form values to a servlet and processing a response. However, the same basic framework is used behind the scenes.
CHAPTER 1 N INTRODUCTION TO SERVLETS 18 Listening for Servlet Container Events There are cases when it may be useful for an application to perform some tasks when it is being started up or shut down. In such cases, servlet context event listeners can become useful. Example Create a servlet context event listener to alert when the application has started up or when it has been shut down. The following solution demonstrates the code for a context listener, which will log application start-up and shutdown events and send e-mail alerting of such events: package org.javaserverfaces.chapter01; import java.util.Properties; import javax.mail.Message; import javax.mail.Session; import javax.mail.Transport; import javax.mail.internet.InternetAddress; import javax.mail.internet.MimeMessage; import javax.servlet.ServletContextListener; import javax.servlet.ServletContextEvent; import javax.servlet.annotation.WebListener; @WebListener public class StartupShutdownListener implements ServletContextListener { @Override public void contextInitialized(ServletContextEvent event) { System.out.println("Servlet startup..."); System.out.println(event.getServletContext().getServerInfo()); System.out.println(System.currentTimeMillis()); sendEmail("Servlet context has initialized"); } @Override public void contextDestroyed(ServletContextEvent event) { System.out.println("Servlet shutdown..."); System.out.println(event.getServletContext().getServerInfo()); System.out.println(System.currentTimeMillis()); // See error in server.log file if mail is unsuccessful sendEmail("Servlet context has been destroyed..."); } /** * This implementation uses the GMail smtp server * @param message * @return */
CHAPTER 1 N INTRODUCTION TO SERVLETS 19 private boolean sendEmail(String message) { boolean result = false; String smtpHost = "smtp.gmail.com"; String smtpUsername = "username"; String smtpPassword = "password"; String from = "fromaddress"; String to = "toaddress"; int smtpPort = 587; System.out.println("sending email..."); try { // Send email here //Set the host smtp address Properties props = new Properties(); props.put("mail.smtp.host", smtpHost); props.put("mail.smtp.auth", "true"); props.put("mail.smtp.starttls.enable", "true"); // create some properties and get the default Session Session session = Session.getInstance(props); // create a message Message msg = new MimeMessage(session); // set the from and to address InternetAddress addressFrom = new InternetAddress(from); msg.setFrom(addressFrom); InternetAddress[] address = new InternetAddress[1]; address[0] = new InternetAddress(to); msg.setRecipients(Message.RecipientType.TO, address); msg.setSubject("Servlet container shutting down"); // Append Footer msg.setContent(message, "text/plain"); Transport transport = session.getTransport("smtp"); transport.connect(smtpHost, smtpPort, smtpUsername, smtpPassword); Transport.send(msg); result = true; } catch (javax.mail.MessagingException ex) { ex.printStackTrace(); result = false; } return result; } } Note N To run this example, you may need additional external JARs in your CLASSPATH. Specifically, make sure you have mail.jar and javaee.jar.
CHAPTER 1 N INTRODUCTION TO SERVLETS 20 Explanation Sometimes it is useful to know when certain events occur within the application server container. This concept can be useful under many different circumstances, but most often it would likely be used for initializing an application upon start-up or cleaning up after an application upon shutdown. A servlet listener can be registered with an application to indicate when it has been started up or shut down. Therefore, by listening for such events, the servlet has the opportunity to perform some actions when they occur. To create a listener that performs actions based upon a container event, you must develop a class that implements the ServletContextListener interface. The methods that need to be implemented are contextInitialized and contextDestroyed. Both of the methods accept a ServletContextEvent as an argument, and they are automatically called each time the servlet container is initialized or shut down, respectively. To register the listener with the container, you can use one of the following techniques: Utilize the u @WebListener annotation, as demonstrated by the solution to this example. Register the listener within the u web.xml application deployment descriptor. Use the u addListener methods defined on ServletContext. For example, to register this listener within web.xml, you would need to add the following lines of XML: <listener> <listener-class> org.javaserverfaces.chapter01.StartupShutdownListener</listener-class> </listener> Neither way is better than the other. The only time that listener registration within the application deployment descriptor (web.xml) would be more helpful is if you had the need to disable the listener in some cases. On the other hand, to disable a listener when it is registered using @WebListener, you must remove the annotation and recompile the code. Altering the web deployment descriptor does not require any code to be recompiled. There are many different listener types, and the interface that the class implements is what determines the listener type. For instance, in this example, the class implements the ServletContextListener interface. Doing so creates a listener for servlet context events. If, however, the class implements HttpSessionListener, it would be a listener for HTTP session events. The following is a complete listing of listener interfaces: javax.servlet.ServletRequestListener javax.servlet.ServletRequestAttrbiteListener javax.servlet.ServletContextListener javax.servlet.ServletContextAttributeListener javax.servlet.HttpSessionListener javax.servlet.HttpSessionAttributeListener It is also possible to create a listener that implements multiple listener interfaces. To learn more about listening for different situations such as attribute changes, please see the section entitled Listening for Attribute Changes. Setting Initialization Parameters It is possible to set initialization parameters for servlets as well. Doing so can be handy in cases where you would like to implement a task with default values if none were given.
CHAPTER 1 N INTRODUCTION TO SERVLETS 21 Example #1 Set the servlet initialization parameters using the @WebInitParam annotation. The following code sets an initialization parameter that is equal to a String value: package org.javaserverfaces.chapter01; import java.io.IOException; import java.io.PrintWriter; import javax.servlet.*; import javax.servlet.annotation.WebInitParam; import javax.servlet.annotation.WebServlet; import javax.servlet.http.*; @WebServlet(name="SimpleServletCtx1", urlPatterns={"/SimpleServletCtx1"}, initParams={ @WebInitParam(name="name", value="Duke") }) public class SimpleServletCtx1 extends HttpServlet { @Override public void doGet(HttpServletRequest req, HttpServletResponse res) throws IOException, ServletException { res.setContentType("text/html"); PrintWriter out = res.getWriter(); /* Display some response to the user */ out.println("<html><head>"); out.println("<title>Simple Servlet Context Example</title>"); out.println("t<style>body { font-family: 'Lucida Grande', " + "'Lucida Sans Unicode';font-size: 13px; }</style>"); out.println("</head>"); out.println("<body>"); out.println("<p>This is a simple servlet to demonstrate context! Hello " + getServletConfig().getInitParameter("name") + "</p>"); out.println("</body></html>"); out.close(); } } To execute the example using the sources for this book, load the following URL into your web browser: http://localhost:8080/JSFByExample/SimpleServletCtx1. The resulting web page will display the following text: This is a simple servlet to demonstrate context! Hello Duke
CHAPTER 1 N INTRODUCTION TO SERVLETS 22 Example #2 Place the init parameters inside the web.xml deployment descriptor file. The following lines are excerpted from the web.xml deployment descriptor for the SimpleServlet application. They include the initialization parameter names and values. <web-app> <servlet> <servlet-name>SimpleServletCtx1</servlet-name> <servlet-class> org.javaserverfaces.chapter01.SimpleServletCtx1</servlet-class> <init-param> <param-name>name</param-name> <param-value>Duke</param-value> </init-param> ... </servlet> ... </web-app> Explanation Oftentimes there is a requirement to set initialization parameters for a servlet in order to initialize certain values. Servlets can accept any number of initialization parameters, and there are a couple of ways in which they can be set. The first example is to annotate the servlet class with the @WebInitParam annotation, and the second way to set an initialization parameter is to declare the parameter within the web.xml deployment descriptor, as demonstrated in the second example. Either way will work; however, the solution using @WebInitParam is based upon the newer Java Servlet 3.0 API. Therefore, Example #1 is the more contemporary approach, but Example #2 remains valid for following an older model or using an older Java servlet release. To use the @WebInitParam annotation, it must be embedded within the @WebServlet annotation. Therefore, the servlet must be registered with the web application via the @WebServlet annotation rather than within the web.xml file. For more information on registering a servlet via the @WebServlet annotation, see the section entitled Registering Servlets Without web.xml. The @WebInitParam annotation accepts a name-value pair as an initialization parameter. In the solution to this example, the parameter name is name, and the value is Duke. @WebInitParam(name="name", value="Duke") Once set, the parameter can be used within code by calling getServletConfig().getInitializationParameter() and passing the name of the parameter, as shown in the following line of code: out.println("<p>This is a simple servlet to demonstrate context! Hello " + getServletConfig().getInitParameter("name") + "</p>"); The annotations have the benefit of providing ease of development, and they also make it easier to maintain servlets as a single package rather than jumping back and forth between the servlet and the deployment descriptor. However, those benefits come at the cost of compilation because in order to change the value of an initialization parameter using the @WebInitParam annotation, you must recompile the code. Such is not the case when using the web.xml deployment descriptor. It is best to evaluate your application circumstances before committing to a standard for naming initialization parameters.
CHAPTER 1 N INTRODUCTION TO SERVLETS 23 Filtering Web Requests Another useful technique can be to apply a filter against a specified URL for a servlet. A filter can then invoke custom processing each time the URL is visited, and the filter will be executed prior to the servlet. Example Create a servlet filter that will be processed when the specified URL format is used to access the application. In this example, the filter will be executed when a URL conforming to the format of /* is used. This format pertains to any URL in the application. Therefore, any page will cause the servlet to be invoked. package org.javaserverfaces.chapter01; import java.io.IOException; import java.io.PrintWriter; import java.util.Date; import javax.servlet.*; import javax.servlet.annotation.WebFilter; import javax.servlet.http.*; /** * This filter obtains the IP address of the remote host and logs * it. * * @author juneau */ @WebFilter("/*") public class LoggingFilter implements Filter { private FilterConfig filterConf = null; public void init(FilterConfig filterConf) { this.filterConf = filterConf; } public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException { String userAddy = request.getRemoteHost(); filterConf.getServletContext().log("Vistor User IP: " + userAddy); chain.doFilter(request, response); } @Override public void destroy() { throw new UnsupportedOperationException("Not supported yet."); } }
CHAPTER 1 N INTRODUCTION TO SERVLETS 24 The filter could contain any processing; the important thing to note is that this servlet is processed when a specified URL is used to access the application. Note N To invoke the filter, load a URL for the application with which the filter is associated. For the purposes of this example, load the following URL (for the previous example) to see the filter add text to the server log: http://localhost:8080/JSFByExample/SimpleServletCtx1. How It Works Web filters are useful for preprocessing requests and invoking certain functionality when a given URL is visited. Rather than invoking a servlet that exists at a given URL directly, any filter that contains the same URL pattern will be invoked prior to the servlet. This can be helpful in many situations, perhaps the most useful for performing logging, authentication, or other services that occur in the background without user interaction. Filters must implement the javax.servlet.Filter interface. Methods contained within this interface include init, destroy, and doFilter. The init and destroy methods are invoked by the container. The doFilter method is used to implement tasks for the filter class. As you can see from this example, the filter class has access to the ServletRequest and ServletResponse objects. This means the request can be captured, and information can be obtained from it. This also means the request can be modified if need be. For example, including the user name in the request after an authentication filter has been used. If you want to chain filters or if more than one filter exists for a given URL pattern, they will be invoked in the order in which they are configured in the web.xml deployment descriptor. It is best to manually configure the filters if you are using more than one per URL pattern rather than using the @WebFilter annotation. To manually configure the web.xml file to include a filter, use the <filter> and <filter-mapping> XML elements along with their associated child element tags. The following excerpt from a web.xml configuration file shows how the filter that has been created for this example may be manually configured within the web.xml file: <filter> <filter-name>LoggingFilter</filter-name> <filter-class>LoggingFilter</filter-class> </filter> <filter-mapping> <filter-name>LogingFilter</filter-name> <url-pattern>/*</url-pattern> </filter-mapping> Of course, the @WebFilter annotation takes care of the configuration for you, so in this case the manual configuration is not required. Note N As of Servlet 3.1 API, if a filter invokes the next entity in the chain, each of the filter service methods must run in the same thread as all filters that apply to the servlet.
CHAPTER 1 N INTRODUCTION TO SERVLETS 25 Listening for Attribute Changes Servlets can perform listening event tasks when HTTP session attributes are changed by implementing the HttpSessionAttributeListener interface. Example This example demonstrates how to generate an attribute listener servlet to listen for such events as attributes being added, removed, or modified. The following class demonstrates this technique by implementing HttpSessionAttributeListener and listening for attributes that are added, removed, or replaced within the HTTP session: package org.javaserverfaces.chapter01; import javax.servlet.ServletContext; import javax.servlet.ServletContextEvent; import javax.servlet.ServletContextListener; import javax.servlet.annotation.WebListener; import javax.servlet.http.HttpSession; import javax.servlet.http.HttpSessionAttributeListener; import javax.servlet.http.HttpSessionBindingEvent; /** * Attribute Listener */ @WebListener public final class AttributeListener implements ServletContextListener, HttpSessionAttributeListener { private ServletContext context = null; @Override public void attributeAdded(HttpSessionBindingEvent se) { HttpSession session = se.getSession(); String id = session.getId(); String name = se.getName(); String value = (String) se.getValue(); String message = new StringBuffer("New attribute has been added to session: n"). append("Attribute Name: ").append(name).append("n").append("Attribute Value:"). append(value).toString(); log(message); } /** * * @param se */ @Override public void attributeRemoved(HttpSessionBindingEvent se) { HttpSession session = se.getSession(); String id = session.getId();
CHAPTER 1 N INTRODUCTION TO SERVLETS 26 String name = se.getName(); if (name == null) { name = "Unknown"; } String value = (String) se.getValue(); String message = new StringBuffer("Attribute has been removed: n") .append("Attribute Name: ").append(name).append("n").append("Attribute Value:") .append(value).toString(); log(message); } @Override public void attributeReplaced(HttpSessionBindingEvent se) { String name = se.getName(); if (name == null) { name = "Unknown"; } String value = (String) se.getValue(); String message = new StringBuffer("Attribute has been replaced: n ").append(name). toString(); log(message); } private void log(String message) { if (context != null) { context.log("SessionListener: " + message); } else { System.out.println("SessionListener: " + message); } } @Override public void contextInitialized(ServletContextEvent event) { this.context = event.getServletContext(); log("contextInitialized()"); } @Override public void contextDestroyed(ServletContextEvent event) { // Do something } } Messages will be displayed within the server log file indicating when attributes have been added, removed, or replaced.
CHAPTER 1 N INTRODUCTION TO SERVLETS 27 Explanation In some situations, it can be useful to know when an attribute has been set or what an attribute value has been set to. This example demonstrates how to create an attribute listener in order to determine this information. To create a servlet listener, you must implement one or more of the servlet listener interfaces. To listen for HTTP session attribute changes, implement HttpSessionAttributeListener. In doing so, the listener will implement the attributeAdded, attributeRemoved, and attributeReplaced methods. Each of these methods accepts HttpSessionBindingEvent as an argument, and their implementation defines what will occur when an HTTP session attribute is added, removed, or changed, respectively. In this example, you can see that each of the three methods listed in the previous paragraph contains a similar implementation. Within each method, the HttpSessionBindingEvent is interrogated and broken down into String values, which represent the ID, name, and value of the attribute that caused the listener to react. For instance, in the attributeAdded method, the session is obtained from HttpSessionBindingEvent, and then the session ID is retrieved from that via the use of getSession. The attribute information can be obtained directly from the HttpSessionBindingEvent using the getId and getName methods, as shown in the following lines of code: HttpSession session = se.getSession(); String id = session.getId(); String name = se.getName(); String value = (String) se.getValue(); After these values are obtained, the application can do whatever it needs to do with them. In this example, the attribute ID, name, and session ID are simply logged and printed. String message = new StringBuffer("New attribute has been added to session: n") .append("Attribute Name: ").append(name).append("n") .append("Attribute Value:").append(value).toString(); log(message); The body of the attributeReplaced and attributeRemoved methods contain similar functionality. In the end, the same routine is used within each to obtain the attribute name and value, and then something is done with those values. A few different options can be used to register the listener with the container. The @WebListener annotation is the easiest way to do so, and the only downfall to using it is that you will need to recompile code in order to remove the listener annotation if you ever need to do so. The listener can be registered within the web deployment descriptor, or it can be registered using one of the addListener methods contained in ServletContext. Although the example does not perform any life-changing events, it does demonstrate how to create and use an attribute listener. In the real world, such a listener could become handy if an application needed to capture the user name of everyone who logs in or needed to send an e-mail whenever a specified attribute is set. Applying a Listener to a Session In the same way that a listener can be applied to an HTTP session to listen for attribute changes, a listener can be applied for performing tasks when sessions are created and destroyedAssume in the following example that you wish to listen for sessions to be created so that you can count how many active sessions your application currently contains, as well as perform some initialization for each session.
CHAPTER 1 N INTRODUCTION TO SERVLETS 28 Example Create a session listener, and implement the sessionCreated and sessionDestroyed methods accordingly. In the following example, a servlet is used to keep track of active sessions. Each time someone works with the application, a counter has one added to it. Likewise, each time a person leaves the application, then the counter goes down by one. package org.javaserverfaces.chapter01; import javax.servlet.annotation.WebListener; import javax.servlet.http.HttpSession; import javax.servlet.http.HttpSessionEvent; import javax.servlet.http.HttpSessionListener; /** * Applying a Session Listener * * @author juneau */ @WebListener public class SessionListener implements HttpSessionListener { private int numberOfSessions; public SessionListener() { numberOfSessions = 0; } public int getNumberOfSessions() { return numberOfSessions; } @Override public void sessionCreated(HttpSessionEvent arg) { HttpSession session = arg.getSession(); session.setMaxInactiveInterval(60); session.setAttribute("testAttr", "testVal"); synchronized (this) { numberOfSessions++; } System.out.println("Session created, current count: " + numberOfSessions); } @Override public void sessionDestroyed(HttpSessionEvent arg) { HttpSession session = arg.getSession(); synchronized (this) { numberOfSessions--; } System.out.println("Session destroyed, current count: " + numberOfSessions); System.out.println("The attribute value: " + session.getAttribute(("testAttr"))); } }
CHAPTER 1 N INTRODUCTION TO SERVLETS 29 Each time a new visitor visits the application, a new session is started, and testAttr is set. When the session times out, then it will be destroyed, and any attributes that have been set for the session will be removed. Explanation A meaningful way to track web application users is to place values in their HttpSession object. Using a Java servlet, session attributes can be set, which will exist for the life of the HttpSession. Once the session is invalidated, the attributes will be removed. To set up a session listener, create a Java servlet, annotate it with the @WebListener annotation, and implement javax.servlet.http.HttpSessionListener. Doing so will force the implementation of both the sessionCreated and sessionDestroyed methods, which is where the session magic occurs. In this example, the sessionCreated method first obtains a handle on the current HttpSession object by calling the HttpSessionEvent object’s getSession method. The handle is assigned to an HttpSession variable named session. Now that you have that variable initialized with the session object, it can be used to set the time of life and place attributes that will live and die with the session’s life. The first session configuration performed in the example is to set the maximum inactive life to 60 (seconds), after which time the servlet container will invalidate the session. Next an attribute named testAttr is set in the session and given a value of testVal. HttpSession session = arg.getSession(); session.setMaxInactiveInterval(60); session.setAttribute("testAttr", "testVal"); A field within the servlet named numberOfSessions is declared, and it is incremented each time a new session is started. Following the session.setAttribute() call, the counter is incremented within a synchronized statement. Finally, a message is printed to the server log indicating that a new session was created and providing the total active session count. Note N Placing the increment within the synchronized statement helps avoid concurrency issues with the field. For more information on Java synchronization and concurrency, please see the online documentation at http://docs.oracle.com/javase/tutorial/essential/concurrency/locksync.html. The sessionDestroyed method is called on a session once the maximum number of inactive seconds has passed. In this example, the method will be called after 60 seconds of inactivity. Within the sessionDestroyed method, another synchronization statement decrements the numberOfSessions field value by one, and then a couple of lines are printed to the server log indicating that a session has been destroyed and providing the new total number of active sessions. Session listeners can be used to set cookies and perform other useful tactics to help manage a user’s experience. They are easy to use and very powerful. Managing Session Attributes It is possible to maintain information throughout the life of an individual session. Servlets can make use of session attributes to retain information on a per-session basis. That information can then be used at any time, so long as the session remains available.
CHAPTER 1 N INTRODUCTION TO SERVLETS 30 Example Make use of session attributes to retain session-based information. To do so, use the HttpServletRequest object to obtain access to the session, and then use the getAttribute() and setAttribute() methods accordingly to set information into the session. In the following scenario, an HTML page is used to capture a user’s e-mail address, and then the e-mail address is placed into a session attribute. The attribute is then used by Java servlets across different pages of the application in order to maintain state. The following code demonstrates what the HTML form (chapter01/sessionAttributeDemo.html) may look like in this scenario: <html> <head> <title></title> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> </head> <body> <h1>Provide an email address to use with this transaction</h1> <br/> <form method="POST" action="SessionServlet"> <input type="text" id="email" name="email"/> <br/> <input type="submit" value="Submit"/> </form> </body> </html> Next, the Java servlet named SessionServlet using a URL pattern of /SessionServlet is initiated when the form is submitted. Any form input values are passed to SessionServlet and processed accordingly. package org.javaserverfaces.chapter01; import java.io.*; import javax.servlet.*; import javax.servlet.annotation.WebServlet; import javax.servlet.http.*; // Uncomment the following line to run example stand-alone //@WebServlet(name="SessionServlet", urlPatterns={"/SessionServlet"}) // The following will allow the example to run within the context of the JSFByExample example // enterprise application (JSFByExample.war distro or Netbeans Project) @WebServlet(name="SessionServlet", urlPatterns={"/chapter01/SessionServlet"}) public class SessionServlet extends HttpServlet { public void doPost (HttpServletRequest req, HttpServletResponse res) throws ServletException, IOException { // Obtain he Session object HttpSession session = req.getSession(true);
CHAPTER 1 N INTRODUCTION TO SERVLETS 31 // Set up a session attribute String email = (String) session.getAttribute ("session.email"); if (email == null) { email = req.getParameter("email"); session.setAttribute ("session.email", email); } String sessionId = session.getId(); res.setContentType("text/html"); PrintWriter out = res.getWriter(); out.println("<html>"); out.println("<head><title>Working with sessions</title></head>"); out.println("<body>"); out.println("<h1>Session Test</h1>"); out.println ("Your email address is: " + email + "<br/><br/>"); out.println ("Your session id: " + sessionId); out.println("</body></html>"); } } In the end, the e-mail address that was entered within the original HTML form was captured and used throughout the different pages in the application. How It Works Since the beginning of web development, session attributes have been used to retain important information regarding a user’s session. This concept holds true when developing using Java servlets as well, and servlets make it easy to maintain attribute values. All HttpServlet classes must implement doGet or doPost methods in order to process web application events. In doing so, these methods have access to the HttpServletRequest object as it is passed to them as an argument. An HttpSession object can be gleaned from the HttpServletRequest, and therefore, it can be used to retrieve and set attributes as needed. In this example, an HTTP session attribute is used to store an e-mail address. That address is then used throughout the application within different servlet classes by obtaining the session object and then retrieving the attribute value. // Obtain the Session object HttpSession session = req.getSession(true); // Set up a session attribute String email = (String) session.getAttribute ("session.email"); if (email == null) { email = req.getParameter("email"); session.setAttribute ("session.email", email); } Any attributes will remain in the HttpSession object as long as the session remains valid. The session ID will remain consistent when traversing between pages. You can see that the solution to this example obtains and prints the current session ID for reference. Using attributes in the HttpSession is a good way to pass data around to maintain a session’s state.
CHAPTER 1 N INTRODUCTION TO SERVLETS 32 Downloading a File Using a Servlet Servlet applications have the ability to download a given file using a series of InputStreams and OutputStreams. Example Write a servlet that will accept the name and path of a chosen file and then read the file and stream it to the file requestor. The following web page can be used to select a file for the servlet to download. Although the following HTML (chapter01/download.html) contains a statically typed file name, it could very well contain a dynamic list of files from a database or other source: <!DOCTYPE html> <html> <head> <title></title> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> </head> <body> <h1>Click on the link below to download the file.</h1> <br/> <a href="DownloadServlet?filename=downloadTest.txt">Download test file</a> <br/> </body> </html> Note N For the example, you can create and edit a file in your root directory next to the WEB-INF folder, and name the file downloadTest.txt to see the servlet transfer the data to your browser client. When a user clicks the link presented on the web page from the previous HTML, the following servlet will be used to download the given file by passing the HttpServletRequest and HttpServletResponse objects to it along with the file that should be downloaded: package org.javaserverfaces.chapter01; import java.io.DataInputStream; import java.io.File; import java.io.FileInputStream; import java.io.IOException; import java.io.InputStream; import java.io.PrintWriter; import javax.servlet.ServletContext; import javax.servlet.ServletException; import javax.servlet.ServletOutputStream; import javax.servlet.annotation.WebServlet; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse;
CHAPTER 1 N INTRODUCTION TO SERVLETS 33 /** * * @author juneau */ // Uncomment the following line to run example stand-alone //@WebServlet(name = "DownloadServlet", urlPatterns = {"/DownloadServlet"}) // The following will allow the example to run within the context of the JSFByExample // enterprise application (JSFByExample.war distro or Netbeans Project) @WebServlet(name = "DownloadServlet", urlPatterns = {"/chapter01/DownloadServlet"}) public class DownloadServlet extends HttpServlet { /** * Handles the HTTP * <code>GET</code> method. * * @param request servlet request * @param response servlet response * @throws ServletException if a servlet-specific error occurs * @throws IOException if an I/O error occurs */ @Override protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { // Read parameter from form that contains the filename to download String fileToDownload = request.getParameter("filename"); // Call the download method with the given file System.err.println("Downloading file now..."); doDownload(request, response, fileToDownload); } /** * Sends a file to the output stream. * * @param req The request * @param resp The response * @param original_filename The name the browser should receive. */ private void doDownload( HttpServletRequest request, HttpServletResponse response, String originalFile) throws IOException { final int BYTES = 1024; int length = 0; ServletOutputStream outStream = response.getOutputStream(); ServletContext context = getServletConfig().getServletContext(); response.setContentType( (context.getMimeType( originalFile ) != null) ? context.getMimeType( originalFile ) : "text/plain" ); response.setHeader( "Content-Disposition", "attachment; filename="" + originalFile + """ );
CHAPTER 1 N INTRODUCTION TO SERVLETS 34 InputStream in = context.getResourceAsStream("/" + originalFile); byte[] bbuf = new byte[BYTES]; while ((in != null) && ((length = in.read(bbuf)) != -1)) { outStream.write(bbuf,0,length); } outStream.flush(); outStream.close(); } /** * Returns a short description of the servlet. * * @return a String containing servlet description */ @Override public String getServletInfo() { return "Short description"; } } The servlet will not produce a response; it will simply download the given file to the end user when the user clicks the link to download the file. Explanation Downloading files is an essential task for almost any web application. Performing the steps that are provided by this example will make it easy to achieve this task. This example demonstrates an easy case in which users can visit a web page, click a file to download, and have the file retrieved from the server and copied to their machine. The HTML is very simplistic in this example, and it lists a URL link that invokes the servlet and passes the name of the file that is to be downloaded. When the user clicks the link, the name of the file is passed to /DownloadServlet as a parameter with the name filename. When the link is clicked, the servlet doGet method is invoked. The first task that is performed in the doGet method is to read the filename parameter from the invoking web page. That information is then passed to the doDownload method along with the HttpServletRequest and HttpServletResponse objects. In the doDownload method, the ServletOutputStream is obtained from the HttpServletResponse object, and the ServletContext is obtained for later use. To download a file, the servlet must provide a response of the same type that matches that of the file to be downloaded. It must also indicate in the response header that an attachment is to be included. Therefore, the first tasks to be performed by the doDownload method involve setting up the HttpServletResponse appropriately. response.setContentType( (context.getMimeType( originalFile ) != null) ? context.getMimeType( originalFile ) : "text/plain" ); response.setHeader( "Content-Disposition", "attachment; filename="" + originalFile + """ ); The file name, in this case originalFile, is used to obtain the MIME type of the file. If the MIME type of the file is null, then text/plain will be returned. The attachment is set up in the response header as well, by appending the file name as an attachment to the Content-Disposition. Next, the doDownload method obtains a reference to the file that is to be downloaded by calling the ServletContext getResourceAsStream method and passing the name of the file. This will return an InputStream object that can be used to read the contents of the indicated file. A byte buffer is then
CHAPTER 1 N INTRODUCTION TO SERVLETS 35 created, which will be used to obtain chunks of data from the file when it is being read. The final real task is to read the file contents and copy them to the output stream. This is done using a while loop, which will continue to read from the InputStream until everything has been processed. Chunks of data are read in and written to the output stream using the loop. while ((in != null) && ((length = in.read(bbuf)) != -1)) { outStream.write(bbuf,0,length); } Lastly, the ServletOutputStream object’s flush method is called to clear the contents, and it is then closed to release resources. The magic of downloading files using a Java servlet may be a bit obfuscated by this example, however, because a static file is being used as the download source in this example. In real life, the HTML page would probably contain a list of files that are contained within a database or on a file system, and then when the user selects a file to download, the servlet will process that file accordingly, even extracting the file from the database if necessary. Dispatching Requests The concept of handing off tasks to other workers to perform action can be mirrored with real-world scenarios. If your car stops functioning properly, you take it to a mechanic. Servlet processing can follow a similar technique by handing off tasks to the appropriate worker servlets. This process is also known as dispatching. Furthermore, servlets have the ability to hand off tasks without redirecting the client to another site, and therefore, the URL in the browser does not change. Example To begin, create a request dispatcher servlet, which will decide which task needs to be completed and then send the request to an appropriate servlet to achieve that task. The following example demonstrates this concept via an HTML form that accepts two numbers from the user and allows the user to decide what type of mathematical evaluation should be performed by the server. The servlet processes the request by first determining which type of mathematical evaluation should be performed and then dispatching the request to the appropriate servlet to perform the task. The following HTML form accepts two numbers from the user and allows them to choose which type of math to perform against the numbers:<html> <head> <title></title> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> </head> <body> <h1>Request Dispatch Example</h1> <p>Perform a mathematical evaluation. Insert two numbers to be evaluated and then choose the type of evaluation to perform.</p> <form method="POST" action="MathDispatcher"> <label for="numa">Enter Number A: </label> <input type="text" id="numa" name="numa"/><br><br> <label for="numb">Enter Number B: </label> <input type="text" id="numb" name="numb"/><br/><br/> <select id="matheval" name="matheval"> <option value="add">Add the numbers</option> <option value="subtract">Subtract the numbers</option>
CHAPTER 1 N INTRODUCTION TO SERVLETS 36 <option value="multiply">Multiply the numbers</option> <option value="divide">Divide the numbers</option> </select> <input type="submit" value="Submit Form"/> <input type="reset" value="Reset Form"/> </form> </body> </html> The next piece of code is the servlet that will dispatch requests accordingly depending upon the value of the matheval field: package org.javaserverfaces.chapter01; import java.io.IOException; import javax.servlet.RequestDispatcher; import javax.servlet.ServletContext; import javax.servlet.ServletException; import javax.servlet.ServletRequest; import javax.servlet.annotation.WebServlet; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; /** * * @author juneau */ // Uncomment the following line to run example stand-alone //@WebServlet(name = "MathDispatcher", urlPatterns = {"/MathDispatcher"}) // The following will allow the example to run within the context of the JSFByExample // enterprise application (JSFByExample.war distro or Netbeans Project) @WebServlet(name = "MathDispatcher", urlPatterns = {"/chapter01/MathDispatcher"}) public class MathDispatcher extends HttpServlet { /** * Handles the HTTP * <code>POST</code> method. * * @param request servlet request * @param response servlet response * @throws ServletException if a servlet-specific error occurs * @throws IOException if an I/O error occurs */ @Override protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { System.out.println("In the servlet...");
CHAPTER 1 N INTRODUCTION TO SERVLETS 37 // Store the input parameter values into Strings String eval = request.getParameter("matheval"); ServletContext sc = getServletConfig().getServletContext(); RequestDispatcher rd = null; int evaluate = 0; int add = 0; int subtract = 1; int multiply = 2; int divide = 3; if(eval.equals("add")) evaluate = add; if (eval.equals("subtract")) evaluate = subtract; if (eval.equals("multiply")) evaluate = multiply; if(eval.equals("divide")){ evaluate = divide; } switch(evaluate){ case(0): rd = sc.getRequestDispatcher("/AddServlet"); rd.forward(request, response); break; case(1): rd = sc.getRequestDispatcher("/SubtractServlet"); rd.forward(request, response); break; case(2): rd = sc.getRequestDispatcher("/MultiplyServlet"); rd.forward(request, response); break; case(3): rd = sc.getRequestDispatcher("/DivideServlet"); rd.forward(request, response); break; } } /** * Returns a short description of the servlet. * * @return a String containing servlet description */ @Override public String getServletInfo() { return "Short description"; } }
CHAPTER 1 N INTRODUCTION TO SERVLETS 38 Next is an example of one of the servlets that the request will be dispatched to. The following is the code for the AddServlet, which will add the two numbers and return the sum to the user: package org.javaserverfaces.chapter01; import java.io.IOException; import java.io.PrintWriter; import javax.servlet.ServletException; import javax.servlet.annotation.WebServlet; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; /** * * @author juneau */ // Uncomment the following line to run example stand-alone //@WebServlet(name = "AddServlet", urlPatterns = {"/AddServlet"}) // The following will allow the example to run within the context of the JSFByExample // enterprise application (JSFByExample.war distro or Netbeans Project @WebServlet(name = "AddServlet", urlPatterns = {"/chapter01/AddServlet"}) public class AddServlet extends HttpServlet { /** * Processes requests for both HTTP * <code>GET</code> and * <code>POST</code> methods. * * @param request servlet request * @param response servlet response * @throws ServletException if a servlet-specific error occurs * @throws IOException if an I/O error occurs */ protected void processRequest(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.setContentType("text/html;charset=UTF-8"); PrintWriter out = response.getWriter(); // Store the input parameter values into Strings String numA = request.getParameter("numa"); String numB = request.getParameter("numb"); int sum = Integer.valueOf(numA) + Integer.valueOf(numB); try { out.println("<html>"); out.println("<head>"); out.println("<title>The Sum of the Numbers</title>"); out.println("</head>"); out.println("<body>"); out.println("<h1>Sum: " + sum + "</h1>"); out.println("<br/>"); out.println("<a href=example01_14.html>Try Again</a>");
CHAPTER 1 N INTRODUCTION TO SERVLETS 39 out.println("</body>"); out.println("</html>"); } finally { out.close(); } } /** * Handles the HTTP * <code>GET</code> method. * * @param request servlet request * @param response servlet response * @throws ServletException if a servlet-specific error occurs * @throws IOException if an I/O error occurs */ @Override protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { processRequest(request, response); } /** * Handles the HTTP * <code>POST</code> method. * * @param request servlet request * @param response servlet response * @throws ServletException if a servlet-specific error occurs * @throws IOException if an I/O error occurs */ @Override protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { processRequest(request, response); } /** * Returns a short description of the servlet. * * @return a String containing servlet description */ @Override public String getServletInfo() { return "Short description"; } } Each of the other servlets is very similar to AddServlet, except the mathematical evaluation is different. To see a full listing of the code, please take a look at the sources for this book.
CHAPTER 1 N INTRODUCTION TO SERVLETS 40 Explanation Sometimes it is a good idea to hide the forwarding of requests from the end user. Other times it just makes sense to hand off a request from one servlet to another so that another type of processing can take place. These are just two examples of when it is handy to perform a request dispatch within a servlet. Forwarding a request versus dispatching a request is different because a forwarded request hands off the request on the client side, whereas a dispatched request hands off the request on the server side. The difference can be quite large since the end user has no idea of server-side dispatches, whereas the browser is redirected to a different URL when the request is forwarded on the client side. Dispatching requests is an easy task. The facilities for doing so are built right into the ServletContext, so once you obtain a reference to ServletContext, then you simply call the getRequestDispatcher method to obtain a RequestDispatcher object that can be used to dispatch the request. When calling the getRequestDispatcher method, pass a String containing the name of the servlet that you want to hand off the request to. You can actually obtain a RequestDisptacher object for any valid HTTP resource within the application by passing the appropriate URL for the resource in String format to the getRequestDispatcher method. Therefore, if you’d rather dispatch to a JSP or HTML page, you can do that as well. After a RequestDispatcher object has been obtained, invoke its forward method by passing the HttpServletRequest and HttpServletResponse objects to it. The forward method performs the task of handing off the request. rd = sc.getRequestDispatcher("/AddServlet"); rd.forward(request, response); In the case of this example, you can dispatch requests to different servlets in order to perform a specific task. Once handed off, the servlet that has obtained the request is responsible for providing the response to the client. In this case, the servlet returns the result of the specified mathematical evaluation. Redirecting to Another Application or Site In certain situations, it can be useful to redirect from a servlet to a different application on the same server or a different site altogether. Example Use the HttpServletResponse object’s sendRedirect() method to redirect from the servlet to another URL. In the following example, when a URL that matches the /redirect pattern is used, then the servlet will redirect the browser to another site: import java.io.IOException; import javax.servlet.*; import javax.servlet.annotation.WebServlet; import javax.servlet.http.*; @WebServlet(name="RedirectServlet", urlPatterns={"/redirect"}) public class RedirectServlet extends HttpServlet { @Override public void doGet(HttpServletRequest req, HttpServletResponse res)
CHAPTER 1 N INTRODUCTION TO SERVLETS 41 throws IOException, ServletException { String site = "http://www.apress.com"; res.sendRedirect(site); } } In this example, the servlet will redirect to the www.apress.com web site. Explanation There are some cases in which a web application needs to redirect traffic to another site or URL within the same or another application. For such cases, the HttpServletResponse sendRedirect method can be of use. The sendRedirect method accepts a URL in String format and then redirects the web browser to the given URL. Given that sendRedirect accepts a String-based URL makes it easy to build dynamic URLs as well. For instance, some applications may redirect to a different URL based upon certain parameters that are passed from a user. Dynamic generation of a URL in such cases may look something like the following: String redirectUrl = null; If(parameter.equals("SOME STRING") redirectUrl = "/" + urlPathA; else redirectUrl = "/" + urlPathB; res.sendRedirect(redirectUrl); The sendRedirect() method can also come in handy for creating the control for web menus and other page items that can send web traffic to different locations. Note N This simple redirect, as opposed to servlet chaining, does not pass the HttpRequest object along to the target address. Utilizing Cookies Within the Browser Securely If an application must maintain state, it should be maintained in a secure manner. Cookies are oftentimes used to pass data around as a means of maintaining state. Servlets can safeguard cookies by marking them as HTTP only.
CHAPTER 1 N INTRODUCTION TO SERVLETS 42 Example Use “HTTP only” browser cookies to save the state. In the following example, one servlet is used to place some session information into a cookie in the browser. Another servlet is then called, which reads the cookie information and displays it to the user. The following servlet demonstrates how to store a cookie in the browser using a Java servlet: package org.javaserverfaces.chapter01; import java.io.IOException; import java.io.PrintWriter; import javax.servlet.ServletException; import javax.servlet.annotation.WebServlet; import javax.servlet.http.Cookie; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; /** * Securing State within the Browser * @author juneau */ @WebServlet(name = "SetCookieServlet", urlPatterns = {"/SetCookieServlet"}) public class SetCookieServlet extends HttpServlet { protected void processRequest(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.setContentType("text/html;charset=UTF-8"); PrintWriter out = response.getWriter(); Cookie cookie = new Cookie("sessionId","12345"); cookie.setHttpOnly(true); cookie.setMaxAge(-30); response.addCookie(cookie); try { out.println("<html>"); out.println("<head>"); out.println("<title>SetCookieServlet</title>"); out.println("</head>"); out.println("<body>"); out.println("<h1>Servlet SetCookieServlet is setting a cookie into the browser</h1>"); out.println("<br/><br/>"); out.println("<a href='DisplayCookieServlet'>Display the cookie contents.</a>"); out.println("</body>"); out.println("</html>"); } finally { out.close(); } }
CHAPTER 1 N INTRODUCTION TO SERVLETS 43 @Override protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { processRequest(request, response); } @Override protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { processRequest(request, response); } } The next code listing demonstrates a servlet that reads the cookies in the browser and prints out the contents: package org.javaserverfaces.chapter01; import java.io.IOException; import java.io.PrintWriter; import javax.servlet.ServletException; import javax.servlet.annotation.WebServlet; import javax.servlet.http.Cookie; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; /** * Securely Maintaining State within the Browser * @author juneau */ @WebServlet(name = "DisplayCookieServlet", urlPatterns = {"/DisplayCookieServlet"}) public class DisplayCookieServlet extends HttpServlet { protected void processRequest(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.setContentType("text/html;charset=UTF-8"); PrintWriter out = response.getWriter(); Cookie[] cookies = request.getCookies(); try { out.println("<html>"); out.println("<head>"); out.println("<title>Display Cookies</title>"); out.println("</head>"); out.println("<body>"); for(Cookie cookie:cookies){ out.println("<p>"); out.println("Cookie Name: " + cookie.getName()); out.println("<br/>"); out.println("Value: " + cookie.getValue()); out.println("</p>"); }
CHAPTER 1 N INTRODUCTION TO SERVLETS 44 out.println("</body>"); out.println("</html>"); } finally { out.close(); } } @Override protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { processRequest(request, response); } @Override protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { processRequest(request, response); } } Explanation Using cookies to store data within the browser is a technique that has been in practice for years. Since Servlet 3.0 API, the ability to mark a cookie as HTTP only has become available. This allows the cookie to be safeguarded against client-side scripting attacks, making the cookie more secure. Any standard servlet can create a cookie and place it into the current session. Similarly, any servlet that is contained within the same session can read or update a session’s cookies values. In this example, two servlets are used to demonstrate how cookies work. The first servlet that is listed is responsible for creating a new cookie and setting it into the browser session. The second servlet is responsible for displaying the contents of the cookie to the user. To create a cookie, simply instantiate a new javax.servlet.http.Cookie object and assign a name and value to it. Passing both the name and value into the Cookie constructor at the time of instantiation can assign a name and value, or it can be done by passing values to the cookie’s setName and setValue methods. Once the cookie has been instantiated, properties can be set that will help to configure the cookie. In this example, the cookie’s setMaxAge and setHttpOnly methods are called, setting the time of life for the cookie and ensuring that it will be guarded against client-side scripting. For a complete listing of cookie properties, please refer to Table 1-3. Finally, the cookie is placed into the response by passing it to the response object’s addCookie method. Cookie cookie = new Cookie("sessionId","12345"); cookie.setHttpOnly(true); cookie.setMaxAge(-30); response.addCookie(cookie);
CHAPTER 1 N INTRODUCTION TO SERVLETS 45 The second servlet, DisplayCookieServlet, is responsible for reading and displaying the session’s cookies values. When DisplayCookieServlet is invoked, its processRequest method is called, which obtains the cookies within the response object by calling response.getCookies() and setting the result to an array of Cookie objects. Cookie[] cookies = request.getCookies(); The cookie object array can now be iterated over in order to obtain each cookie and print out its contents. The servlet does so by using a for loop and printing out each cookie’s name and value. for(Cookie cookie:cookies){ out.println("<p>"); out.println("Cookie Name: " + cookie.getName()); out.println("<br/>"); out.println("Value: " + cookie.getValue()); out.println("</p>"); } Finalizing Servlet Tasks It is easy to perform cleanup tasks within the context of a servlet. Example To cleanup or perform finalization within a servlet, first provide code for performing any cleanup within the servlet destroy method. Second, in the case that there are potentially long-running methods, code them so that you will become aware of a shutdown and, if necessary, halt and return so that the servlet can shut down cleanly. The following code excerpt is a small example of a destroy method. In this code, it is being used to initialize local variables and is setting the beingDestroyed boolean value to indicate that the servlet is shutting down. Table 1-3. Cookie Property Methods Property Description setComment Sets a comment to describe the cookie. setDomain Specifies the domain in which the cookie belongs. setHttpOnly Marks the cookie as HTTP only. setMaxAge Sets the maximum lifetime of the cookie. A negative value indicates that the cookie will expire when the session ends. setPath Specifies a path for the cookie to which the client should return it. setSecure Indicates that the cookie should be sent only using a secure protocol. setValue Assigns a value to the cookie. setVersion Specifies the version of the cookie protocol that the cookie will comply with.
CHAPTER 1 N INTRODUCTION TO SERVLETS 46 ... /** * Used to finalize the servlet */ public void destroy() { // Tell the servlet it is shutting down setBeingDestroyed(true); // Perform any cleanup thisString = null; } ... The code within the destroy method may successfully achieve a full cleanup of the servlet, but in the case where there may be a long-running task, then it must be notified of a shutdown. The following excerpt is a block of code that signifies a long-running task. The task should stop processing once the shutdown is indicated by the beingDestroyed value becoming true. for (int x = 0; (x <= 100000 && !isBeingDestroyed()); x++) { doSomething(); } Explanation The finalization of a servlet can be very important, especially if the servlet is using some resources that may lead to a memory leak, making use of a reusable resource such as a database connection or in order to persist some values for another session. In such cases, it is a good idea to perform cleanup within the servlet destroy method. Every servlet contains a destroy method (which may be implemented to overload default behavior) that is initiated once the servlet container determines that a servlet should be taken out of service. The destroy method is called once all of a servlet’s service methods have stopped running. However, if there is a long-running service method, then a server grace period can be set that would cause any running service to be shut down when the grace period is reached. As mentioned earlier, the destroy method is the perfect place to clean up resources. However, the destroy method is also a good place to help clean up after long-running services. Cleanup can be done by setting a servlet-specific local variable to indicate that the servlet is being destroyed and by having the long-running service check the state of that variable periodically. If the variable indicates that the destroy method has been called, then it should stop executing. Reading and Writing with Nonblocking I/O First generation web applications oftentimes were plagued with the user clicking a button to submit a request to perform a read or write operation, and then waiting for a period of time so that the task could complete. Sometimes this was a momentary wait, and other timesit was a longer wait. Modern implementations of the Servlet API make it possible to perform asynchronous I/O, helping to alleviate this issue. Example Use the Non-Blocking I/O API that is part of the Servlet 3.1 release to create an asynchronous solution. To use the new technology, implement the new ReadListener interface when performing nonblocking reads, and implement the WriteListener interface for performing nonblocking writes. The implementation class can then be registered to a ServletInputStream or ServletOutputStream so that reads or writes can be performed when the listener finds that servlet content can be read or written without blocking.
CHAPTER 1 N INTRODUCTION TO SERVLETS 47 The following sources are those of a ReadListener implementation that reside in the source file org.javaserverfaces.chapter01.AcmeReadListenerImpl.java, and they demonstrate how to implement the ReadListener: package org.javaserverfaces.chapter01; import java.io.IOException; import java.util.logging.Level; import java.util.logging.Logger; import javax.servlet.AsyncContext; import javax.servlet.ReadListener; import javax.servlet.ServletInputStream; public class AcmeReadListenerImpl implements ReadListener { private ServletInputStream is = null; private AsyncContext async = null; public AcmeReadListenerImpl(ServletInputStream in, AsyncContext ac) { this.is = in; this.async = ac; System.out.println("read listener initialized"); } @Override public void onDataAvailable() { System.out.println("onDataAvailable"); try { StringBuilder sb = new StringBuilder(); int len = -1; byte b[] = new byte[1024]; while (is.isReady() && (len = is.read(b)) != -1) { String data = new String(b, 0, len); System.out.println(data); } } catch (IOException ex) { Logger.getLogger(AcmeReadListenerImpl.class.getName()).log(Level.SEVERE, null, ex); } } @Override public void onAllDataRead() { System.out.println("onAllDataRead"); async.complete(); }
Other documents randomly have different content
WHAT HAPPENED AT MOOSE FACTORY DURING SUMMER AND FALL, 1920 Extracts from the Post Journal from Entries by J. L. Gaudet, Post Manager July 1st—Our steamer, the "Inenew," left this morning on her first trip to Charlton Island, taking the District staff to the island for the summer, as this is our summer distributing point. Dr. Stewart and Rev. W. G. Walton were passengers. July 6th—The steamer returned with a cargo for Moose Factory of Charlton Depot stock. The steamer returned to Charlton with a load of lumber which I am shipping to the Straits. July 14th—The steamer returned with her second cargo from Charlton, and took another load of lumber for the Strait Posts. Mr. Johansen of the Biological Branch of the Naval Department of the Canadian Government, was a passenger on his way to Fort George. Mr. Fred McLeod and family were also passengers on their way to Woswonaby Post. Mr. McLeod is going there in the capacity of Post Manager. July 21st—Mr. F. D. Wilson arrived here to-day with two apprentice clerks, Messrs. Beveridge and Findlay, both from Aberdeen, Scotland. Aug. 3rd—Mr. Aurey, the government treaty paymaster, arrived here on his annual trip, paying treaty to the Indians. Mr. Aurey is assisted by Dr. Baker. Aug. 10th—Mr. Russell and family, Mr. John Louttit and family, arrived with the schooner "Fort George." These gentlemen are on their way out to civilization. Mr. Russell was in charge of Fort George Post. Aug. 14th—Mr. Romanet, general fur trade inspector, arrived here with Mrs. Romanet and two children. Mr. Romanet says he is here on an official visit from the Fur Trade Commissioner's Office. Inspector Phillips and Sgt. Joy, of the R.C.M. Police, also arrived to-day. They are on their way to the Belcher Islands to investigate some Eskimo murder case. Aug. 17th—A large seaplane, "The Caaz," with Capt. Maxwell as pilot and Mr. Doan as engineer, landed here this afternoon. This is the first flying machine to come to Moose Factory and was quite a sight for our Indians. Aug. 19th—The general inspector left on the schooner "Fort George" for Charlton Island this morning at 7 o'clock. A canoe carrying the ship's papers and two apprentice clerks, Mr. Gregory and Mr. Bremner, arrived at 1 p.m., just a few hours late to catch the schooner which I was holding for that purpose, so I had to get busy and send off our hay-boat with this mail to Charlton Island. Aug. 23rd—The seaplane landed here to-day on her second trip from Remy Lake, which is a few miles from Cochrane, with two moving picture men, Mr. Blake and Mr.
Tash. They claim that they are being sent by the Ontario Government to take pictures. Aug. 26th—We had a visit from Capt. Mack to-day. He came with our schooner "Fort Charles" from Charlton Island, and states that they had a hard and trying trip coming through the Straits. Mr. and Mrs. Mayer were also passengers. Mr. Mayer is our worthy Post Manager at Great Whale River and is on his way out to civilization on a few months' leave. Aug. 27th—The seaplane "Caaz" brought us some newspapers from Cochrane, dated Aug. 25th, with the latest news. Aug. 31st—We have at last managed to extinguish the bush fire which was started by the Rev. Mr. Haythornthwaite on the 25th inst., after working day and night since it started. This will be quite a relief to the many families who are still camped across the river, as they were afraid to come back. Sept. 2nd—Our steamer "Inenew" landed here to-day with our District Manager, Mr. Rackham, Mr. Romanet, the general inspector, Mr. Griffith, manager of Albany Post, who is acting as private secretary to the general inspector, Messrs. Blake and Tash, movie men, and the Rev. Mr. Walton were passengers. The seaplane "Caaz" also arrived from Remy Lake with Mr. Griffin, representing the Toronto Star, as passenger. Sept. 21st—Mr. A. Nicolson and family arrived this evening from Rupert's House, after a hard and trying trip around the coast. Mr. Nicolson has been in the employ of the Hudson's Bay Company for forty years. It is with much regret that we see Mr. Nicolson severing his active services with the good old Company. Sept. 23rd—Mr. and Mrs. J. W. Anderson and child landed here to-day after spending a few months' holiday in civilization. Mr. Anderson is on his way to his Post, which is Attawapiskat. Oct. 1st—The steamer "Inenew" landed here to-day with the District Office staff and the balance of our outfit. This finishes our season's transport. Oct. 7th—Capt. G. R. Redfearn, A. Guibeau, engineer, Inspector Phillips, Sgt. Joy, Mr. Johansen and Mr. Sainsbury left this morning for Clute. Oct. 9th—Hauled out the S.S. "Inenew" to winter quarters and stored away the hauling gear. Oct. 27th—Packet canoes returned from the line to-day and by them received the first issue of our magazine, The Beaver. Oct. 29th—Mr. G. R. Ray, fur trade inspector, and Mr. J. B. Neil arrived here to-day at mid day. Nov. 10th—The river is frozen over, and hardly any snow on the ground as yet. We are having fine weather.—J. L. Gaudet, Post Manager.
The Ghost is Foiled in Lac Seul's Haunted Room By R. O. OTTEN It was Christmas at Lac Seul Post, that historic place, well known to men of the North. Quite a number of the Outpost managers had come in to spend Christmas with the Post Manager and his family. The last to arrive was Mr. R. He had travelled over 200 miles by dog team and cariole to get there. After the hand-shaking was over, Mr. M., the Post Manager, drew Mr. R. aside and asked if he believed in ghosts. Mr. R. laughed and said he didn't believe in any kind of spirits, except the kind they used to have at Christmas in the old days, but wanted to know what the joke was. The Post Manager told him that he had only one room left vacant, and nobody had slept in that room for years as it was supposed to be haunted. The story was that on two different occasions at the usual Christmas gathering of the Outpost managers, there had been tragic endings to several guests who had occupied that room. Both had died from having their throats cut from ear to ear—and no one had slept there since. Mr. R. said he didn't believe in such nonsense as ghosts, and wanted to be shown to the room, as he wanted to get a shave and clean-up before dinner. He said any kind of a room would look good to him after sleeping in the snow for the past week. The Post Manager showed him to the room which was situated at the rear of the large dwelling house, away from the rest of the guests. Mr. R. had just laid out his "glad rags" and was commencing to shave—he had the razor in his hand—when a feeling came over him that he was not alone in the room. Looking into the mirror, he was horrified to see there the reflection of a horrible face peering over his shoulder. He felt his wrist grasped by a claw-like hand. His hand was being forced slowly up and up, towards his throat. Mr. R. tried to call out for help, but he was powerless to utter a sound. The hand was still forcing the razor towards his victim's throat, then it started to draw it across. Mr. R. gave himself up for lost, when he felt the grip on his wrist loosen and a baffled expression came over the horrible face. That ghost was up against modern science. Mr. R. was using a safety razor.
SASKATCHEWAN DISTRICT OFFICE NEWS Congratulations would appear to be in order for Mr. and Mrs. Armstrong, of Fort a la Corne Post, and their daughter Norah on the success attained by the latter at the recent St. Alban's College (Prince Albert) term examinations. The following is a quotation from the local paper: "Miss Norah Armstrong, the gold medalist of the year at St. Alban's college, Prince Albert, holds an enviable record in the college. Miss Armstrong has been a student at St. Alban's for the past four years, taking her grade 8 diploma in 1917. She was successful in passing her junior matriculation examination in June, and now holds the St. Alban's scholarship to the University of Saskatchewan. In addition to her marked progress in her studies, Miss Armstrong has found time to distinguish herself along athletic lines, having won the tennis cup in singles, and also with Miss Phyllis Clarke in the doubles."
"SKIPPERING A SCOW" ON THE ATHABASCA (Continued from last number) By N. A. Howland When the men in the scow realized their position they did not shout frenziedly for help. To them the most important business of the moment was to get a smoke. They Smoked While Facing Death The frenzied people were all on shore. Under the calming influence of tobacco, the wrecked crew surveyed the damage. The boat was intact though leaking a little. It was impossible for them to extricate themselves. Even if any of them could swim, an attempt to make the shore would have proved fatal. They relied on us. Their hope was founded on a rock as surely as their craft. Getting Ready for the Rescue It was not long ere some of the sixty odd men, at Mr. Cornwall's direction, on the island had run to the warehouse to get rope. Fortunately being on the scene, he took matters in hand, and as soon as the necessary tackle had been brought, essayed to rescue the endangered crew. The only way that this could be done was to get a line aboard the scow and pull her off. The distance from shore was too great to permit of a rope being thrown, but there was a rock standing well out of the water about half way between, from which it might be possible to hurl a stick; so Cornwall, taking a club in his hand to which was attached a long cord held by the men on shore, started to work his way out to the vantage point through the rock-studded stream, struggling from boulder to boulder, the swirling water gripping and tearing at his legs in an effort to sweep him away. Fighting the Torrent
To the tense crowd of men watching it seemed impossible that he could attain his object, but in spite of the great physical strain slowly and surely the figure—now waist deep in the current, now pulling himself up on to a rock, clinging always to the meagre support with a tenacity that the raging torrent could not break—reached its goal. Getting A Line Aboard the Wreck A sense of relief came to those who watched, but not for long. He rested for a moment to recover his breath; then coolly gathering the small rope into a coil he made the first throw. A gasp went up from the crowd on shore. The distance was too great; the stick hit the water fully twenty feet short. Again and again the attempt failed. Sometimes the missile fell so close that the rope could almost be reached but they had no boat-hook aboard. The thrower could not stand up with good footing to do his work, but from a precarious position threw with arms alone. He rested, tired by his exertions. Suddenly he gathered all his strength and at imminent hazard of hurling himself into the river sent the stick with unerring aim over its mark. We Pulled the Scow Off the Rock A mighty cheer went up from all the watchers. It was but a moment's work to haul in the cable and make it fast to the end of the scow; every available man on shore found a place on the line, and pulled with might and main to the cry of "Yo heave ho!" that she creaked in every seam and her square end was drawn bow-shaped under the strain on that fragile rope. Pull as we might, our efforts to dislodge her were unavailing. Something had to give, however. It was the line which parted with a snap, hurling us to the ground. A groan went up from those in danger, for in a moment they fell from the highest hope to the lowest depth of despair. They were in worse plight than before, but steadfastly the business of renewing communication with the scow proceeded without delay. Cornwall's efforts were again crowned with success. Little by little our task was accomplished and we were gratified to see the men who were in the water scramble aboard in great haste, as with a rousing cheer we let go the cable. A Tenderfoot Spectator When we had first arrived at the head of the rapids the previous day, a little man with a large outfit was found encamped on the river bank unable to proceed any further, waiting for something or somebody to turn up. Ten days had passed before help arrived. He had been brought hither by a gasoline engine and canoe, his only companions so far as is known being two spaniels. This gentleman styled himself a prospector ostensibly bound for Fond-du-Lac to investigate the silver strike there; but his proceedings and appearance belied the assertion, for if there were a man who should not have left the shelter of the paternal wings, it was he. The impression gained was that he was one of those helpless useless atoms of humanity that are misfits anywhere, but in the North, where one must be self-reliant, doubly out of place. He having arranged with Mr. Cornwall for a "lift" from there to Fort McMurray, lay all day on his bedding in the sand surrounded by his goods and chattels, playing with his dogs, bestirring himself only to take a photograph occasionally or get a bite to eat. Fondled His Spaniels and Looked On
He was apparently oblivious to the tragedy being enacted within a hundred yards of him. This man called down upon himself the contempt and scorn of all men present by remaining inert, lazily fondling his spaniels whilst men's lives trembled in the balance. His hand upon the rope would not perhaps have helped much, but we should at least have known that he was a man. The sequel to his apathy was that next day he was deposited on the main land below the rapids and where it was intimated to him that his company was no longer desirable. An All Night Mosquito Raid Whether fired by a spirit of recklessness by the events of the day, or whether the writer was too tired to return to his camp on the mainland with the men is of little consequence, but be it known that his mosquito-bar was there. Needless to say, the mosquitoes were victorious. We needed no alarm clock that morning because the enemy forced me out of bed during the night to upbraid myself for a fool. Not a wink of sleep for me as a result; however, we got an early breakfast out of it. The Tug "Crester" Wrecked My Russians were making good progress removing the rails, the freight having been all portaged, and the scows run through the previous day were being drawn up to the Island and reloaded. About 10 o'clock Captain Barber started to run the tug "Crester" through the rapids without steam, steering with auxiliary in case of accident. Disaster dogged the footsteps of the railroad party apparently. Nothing had gone well so far. The climax had arrived. Those who were watching the river gave a shout. All eyes went to the rapid immediately; there was the "Crester" shooting down through the roughest of the water well over on the land side, out of control. We learned later that her rudder had been smashed. We saw her take a few bad bumps from a distance of two hundred yards; then with a final heave she seemed to be lifted bodily and dashed on the rocks close inshore where she lay a wreck with her bottom stove in, broadside to the current with the waves breaking over her.
The "Crester" Dismantled There were no casualties. With the aid of spars, the crew were easily able to make the land. It was the middle of the afternoon before it was possible for me to go over and see the tug. In the space of six hours the captain, engineer and boatmen had her completely dismantled and all her "innards" ashore, whilst preparations were being made to pull her off and float her down the rest of the way into the Big Eddy, where she could be patched up. (To be continued)
Moose Island Afire Clergyman's Bonfire Grows Into Conflagration, Threatening H.B.C. Post and Natives' Homes BY GEO. FINDLAY, Moose Factory A Journal extract, dated August 25th, 1920, states briefly that: "The Rev. Mr. Haythornthwaite while burning old tree stumps at the back of the Mission allowed the fire to run on, thereby setting alight the adjoining bush." That day, a Wednesday, was excessively hot, and, as the whole summer had been very warm, all the bush and undergrowth must have been perfectly dry. At 2 o'clock in the afternoon the cry of "Fire" went up, and from the southwest end of the island a big column of smoke began to darken the air, blowing in the direction of the Post. For some minutes the natives stood gazing and then the realization that the Island was afire broke upon them. Something akin to panic set in. Canoes were loaded. Food, blankets and tents were thrown haphazardly into them, and they were swiftly paddled to the opposite bank of the river by the fear-stricken natives. Imagine the scene: The river dotted with canoes, with their multicoloured loads; the roar of the ever-increasing fire, as it was fanned by a slight breeze, and the strange stillness that pervaded the Post, which can be sensed only in a deserted place. The servants returned as soon as their families were safely "entrenched" on the other side of the river, and each with his axe hurried to the scene of the outbreak. In company with Mr. Gaudet, our Post Manager, I went to see the progress made by the fire. Often we were compelled to change our route through the bush on account of the terrific heat and the choking, blinding smoke. In many places great patches of undergrowth were blazing quite a distance from the body of the fire, sparks having been blown ahead by the wind. The roar of the fire was deafening as it caught fresh trees, shooting great lurid tongues of flame up their entire thirty feet. Darker and darker grew the air; the heat became fiercer; the fire advanced as if to satisfy its terrible hunger by enveloping the entire Island in its scorching clutch; and as we walked back to the deserted Post thoughts of having to abandon it ran through our minds. However the wind dropped, and the little band of fire fighters worked hard to accomplish their task. Had the wind risen, the whole island would have been devastated. All that night, and the succeeding five days and nights, gangs of natives (who had by this time got over their fright) and servants watched the fire until it was successfully stamped out.
Assembly of Indians who received H.B.C. Long Service Medals at Fort Alexander Robust sons of Post manager W. A. Murray, at Fort Alexander, Manitoba
Javaserver Faces Introduction By Example Juneau Josh
WINNIPEG RESOLVED Jan. 1, 1921 that New Year's resolutions are not going out of fashion, as witnessed by the following answers to the query, "What is One of your New Year's Resolutions." J. H. Pearen—To remain young that I may laugh with my children. To be considerate at all times of the aged and infirm or those in need of encouragement. W. Ogden—To think more, talk less and to go through each day fully realizing that the opportunities which come to me lie in the present and not in the future. Thos. F. Reith, Card-writer—That I try to emulate the well-known Beaver and turn out heaps of Bright Effective Artistic Vigorous Enterprising and Readable show cards, tickets and signs during 1921, in which case I expect to "BE-A-VER-"Y busy Card-writer. Geo. W. Ashbrook—It is my opinion that a New Year's resolution, if sincere, should be confined to the individual's eye alone and not open to the gaze of the public. S. Kaufman—One of my resolutions for 1921 is to endeavor to reduce my weight twenty pounds by applying myself assiduously to the royal sport of curling during the winter season and by strenuously playing tennis during leisure hours in the summer time. Miss D. Bens—To be true to my word, my work and my friends. To make all I can, to save all I can and give all I can. J. W. Frankish—We are aiming at 100% efficiency in selling our merchandise. It should be sold on the same basis as we buy it. More attention by sales staff in introducing all the new merchandise as it enters the department. This is our intention in departments 3 and 5 for 1921. Chas. Healey—Do it now! This is my New Year's resolution. It is so easy to put things off when just a little "pep," a little extra energy is needed. So much can be gained and greater satisfaction can be given to all. Do it now! A. C. Dunbar—I will increase my efficiency—(power to produce)—by studying, plus analyzing, plus determination, plus application, equals increased efficiency.
J. Whalley—That every business act of mine will be executed with the full belief that it is for the best interest of the firm. Saml. Drennan—To continue placing more confidence in the washboard than in the Ouija board. I. N. Cognito—Not to engage any more handsome looking salesgirls, as those I now have are all engaged—and may get married. W. R. Ogston—One of my resolutions for the New Year will be to govern my actions, thought and speech towards my fellowmen by the well-known principle of "The Golden Rule" and to do my work in such a way that at the close of each day I may feel that I have accomplished something. Winnipeg Moustache Club Semi-Annual Report Just prior to the closing of the outfit ending January 31st, 1920, a careful inventory discloses the following state of affairs. The showing is not entirely satisfactory, but it is felt that some progress is being made. Moustaches on Hand—None. Moustaches on Upper Lip—Twenty divided among the following "heads of stocks": Messrs. Frankish, Goody, Grant, Moore (tailoring), Lade, Fuller, Hughes, Lackie, Weeden, Blowers, Leveque, Dickens, Harrison, Hardiman, Keeley, Chambers, Duckneau, Breitner, Clark, Pugsley (?). New Member—Mr. T. Nichols. (Greetings, brother). Under Suspicion—Mr. C. M. Thomas, Mr. C. Robinson, Mr. Robt. Cunningham. The Club's National Anthem—"The Bonnie Bloomin' Heather." Legend for Club's New Escutcheon—"The Weight of a Hair Will Turn the Scales."— Shakespeare. Remarks—All members and supporters are urged to consult Mr. Saalfeld re irregularities of growth observed from time to time. Renovation for spring should be undertaken early. Special rates to members for loan of Hoover electric sweepers. Use of garden rakes or weeders will result in suspension from Club privileges. Special attention is called to the alarming recurrence of the grasshopper plague prophesied for June and July.
DO YOU REMEMBER this remarkable aggregation? This is the formidable H.B.C. Football Team, Season 1911-12. From left to right—Madill, Jones, Medland, Isaacs, Everitt, Paul, Brodie, Dyde, Foulks, Sheldon, Campbell, Mr. A. H. Doc, Law, Smith, Allan. Managers' Social Dramatic Affair As merry a company as ever graced a festal board met at the store buyers', managers' and assistants' social in the lunchroom, Thursday evening, January sixth. The highly edible and diversified "wittles" were disposed of with a display of "wim" and "wigor" which did justice to all traditions. Entire arrangements for the occasion were undertaken by the ladies, and the zest with which the entertainment proceeded brought down the applause of the whole assembly. Speech, anecdote, jest, song and a three-act drama, starring the celebrated tragedian, Samuel Drennan, were features of an altogether enjoyable and profitable evening. Are We 100 Per Cent Efficient? By R. J. HUGHES I wonder how many of us could answer the question at the head of this article truthfully without a considerable amount of self-study, and if we did stop and analyze ourselves would we find that we could say, "Yes, I am 100 per cent. efficient." Now, let us consider for a minute what "efficient" really means. Turning to your dictionary, you will find the definition, "capable of producing the desired results." Are we really prepared to say "yes, I am capable of producing the desired results." If you can't, you are not 100 per cent. efficient and must find the reason why. It does not matter what position you hold or what the nature of your work is, if you are efficient, advancement is bound to be waiting. In a recent issue of The Beaver was a copy of what was called "A man-rating chart" and a statement that stores' staff promotions are governed by efficiency. Study this chart and
see how many points you can honestly claim to have mastered. Whatever you do, don't go round like some people saying, "I am 100 per cent. efficient." If you really are, the management will soon notice it and promotion will come your way. Next month I will tell you what an important part memory takes in efficiency. Y-O-U! What's the Matter With You, Anyway? By ELMER PUGSLEY There are two ways, 'tis said, by which to get into "society"—either by flattering or shocking it. But though the writer had the honeyed tongue of the anteater, this is no time to coddle and soothe you with some linseed-poultice sort of caressing lullaby. It's New Year's and I am deliberately setting out to fire up your "dander." Of course, you may be able to prove an alibi, but, otherwise, if these few plodding lines succeed in making you really boiling, red-hot "mad"—(not just angry, you understand)—that will be the best proof that you're still conscious—and there's hope for you. We shudder when we read of "so and so" being picked up unconscious, but I could pick up numbers of people in that pitiable predicament any day—people who somehow got into the business world, strange to say. You stand at the outset of a New Year. Scientists think there have been living beings on this old planet for 500,000 of those time-measures we call years—but there is only one you can be sure of—that's this year. It's a wonder you didn't think of that without being told! Glance back over the old year's glimmering trail now fading into whatever such things fade into. It is strewed with regrets and wasted opportunities that slipped through your careless fingers! Aren't you ashamed? What's the matter with you anyway? Don't you care much? Aren't you interested in the big proposition called "life", more than just enough to watch the procession of progressive mortals passing? You'll never keep up with them if you don't pad right along! Wouldn't you like to strike out for a real goal, eh? You have the stuff in you if you'd just shake yourself a little to rouse your rusting gifts. Don't turn over the key to the bailiff just because you weren't born under a favorable sign in the zodiac. Even if your teacup doesn't read right—pshaw! you wouldn't let a thing like that spoil your future! Never mind if the bumps on your head are in the wrong place; jump into the scuffle and you'll receive any other bumps you need before you're through. A chap is said to have advertised his brains for sale the other day—"good as new—never been used." He never served in The Hudson's Bay, that fellow. No, sir! The very air is surcharged with pleas to you to launch out and distinguish yourself. Self advancement is the theme of the age. No one can do as much for you as you can do for yourself. You're a regular "powerhouse" of possibilities if you have enough gumption to utilize them. You remember you turned down a smashing good chance to get ahead, when, for the sake of a few paltry frivolities, you sacrificed that special study course which you could have mastered in 1920. You know better than that. You saunter along
through life as if you had a thousand years to put in here. Train the microscope on your freckled career and set about to remedy things. Come now, get hold of yourself! It's all beginning over again—New Year—new page—new everything! Tackle something that's so much bigger than you that it scares you! That's the way to grow accustomed to accomplishing big things. This is your year! How do you know that you're going to have another as good? Make this your motto—pin it to your New Year's resolutions—"This is My Year!"—and in sooth it will be your year! Miss McCheyne's name was inadvertently omitted from the formerly published list of names of those completing ten years' service. Since the change in markets Miss Winslow, our postmistress-in-general, is worried for fear someone is going to tear in one of these days and ask what the new replacement price is on two cent postage stamps. Someone turns in an unsigned report about the prevalence of "sparklers" getting hard on the eyes around the bureau of adjustment. First Snowshoe Tramp By Land Staff Eighteen members of the Land Department staff snowshoed out to the home of Mr. B. Everitt, our genial associate editor, at East Kildonan, Saturday evening, December 18th. The party gathered at Redwood bridge and tramped north by way of Red River. About half way it was found necessary to call a halt owing to the guide being missing. His rejuvenated appearance upon eventually overtaking the main party led to some doubt as to the generally accepted meaning of "air holes," which were reported to be the cause of the delay. While there was not sufficient snow to make real good tramping, what was lacking in this respect was more than compensated for by the enjoyable time provided by the host and hostess at the conclusion of the hike. Here games and dancing were indulged in until midnight, when the party was brought to an end with the singing of "Auld Lang Syne."— F.H.N. An Error Rectified As some error in the names of the long service medalists had been made at the opening of the Anniversary Celebration, our general manager's office was the scene the other day of a pleasant little ceremony when Mr. Chas. E. Robinson was made the recipient of his long service medal. It was presented by Sir Augustus Nanton, chairman of the Canadian Advisory Committee, Mr. FitzGerald and Mr. Sparling being also present. "Charlie" has been with the Store since June 6, 1904, and is one of the bulwarks. Mr. James Thomson, former Commissioner of lands and furs, was warmly welcomed home at Winnipeg, December 23rd, after an absence of several months in the Orkney's and Scotland.
EDMONTON LAND OFFICE Our photograph shows Mr. J. R. McIntosh, H.B.C. Land Agent in charge of the Edmonton Land Office, with his secretary and Mr. Henderson (standing). Mr. McIntosh and staff who are actively associated with the Company's housing scheme, operate from these modern offices in the McLeod Building. Retail Store Notes Recent Changes Among Store's Department Heads Changes never seem to come singly, for since the first appearance of The Beaver no less than five important executive appointments have been made in the store; and another is scheduled for the very near future. Mr. Chasey, the new buyer for the men's clothing departments, and Miss M. Doherty, the new buyer for the hosiery and gloves, are now firmly established on their feet and are making noteworthy progress. We now welcome to our ranks three more recent arrivals:
Mr. Pallett is another Easterner who has heard the call of the West. Mr. Pallett succeeds Mr. Jenkins as buyer of the trimmings and ribbons. He was previously with the T. Eaton Company for several years. Mr. Pallett is very favorably impressed with the City of Edmonton and predicts a great future for the store. Mr. Secord is the new buyer of the ladies' ready-to-wear, and successor to Mr. Woodman. Mr. Secord was previously with the Robert Simpson Co., of Toronto, nine years buyer of the ladies' ready-to-wear and fur department. Since coming to the store, Mr. Secord has won the esteem of the entire staff and we predict a rosy future for the department under his supervision. Mr. J. McLeod has succeeded Mr. McKee as buyer of the cigar and candy departments. Mr. McLeod was recently floor manager on the second floor and was previously manager of the grocery department, Hudson's Bay Company, Retail, Vernon, B.C. Hail to Our New Assistant "Chief" This new appointment was effective on December 13th, 1920. Besides holding the position of assistant manager, Mr. McKenzie will also act in the capacity of merchandise manager, thereby relieving Mr. F. F. Harker of a big burden. Mr. Harker has for the past twelve months acted in the dual capacity of manager of the store as well as merchandise manager. Mr. G. M. McKenzie was born in Edinburgh, Scotland, serving his apprenticeship in the dry goods and men's wear business. In 1901 he came to Canada and joined the firm of Jaeger & Company, subsequently holding the position of stores manager and supervisor of the factory in Montreal. In 1916 Mr. McKenzie heard the call of his country and proceeded to the front, serving with His Majesty's forces in France until March, 1919. Upon returning to Canada he accepted a position with the R. J. Tooke Company as general manager of the retail stores in Montreal. His recent appointment as assistant manager of the Edmonton store will fill a long felt want.
Mr. P. A. Stone, president of the Amusement and Athletic Association, which has grown to embrace a dozen varied athletic and social activities since its inauguration in September, 1919. Mrs. Lewis recently rejoined the staff after an absence of two years. She is in charge of the lace and neckwear department. We are glad to welcome her back. Miss Law is also an old member of the staff who has recently come back to the store. During her absence she was with the Company's store at Calgary. She is resuming her duties here in the ribbon department. Miss McAdam, who has been in the Company's service for the past seven years, has left us for the coast. Miss McAdam was a very popular member of the staff and we regret
exceedingly to lose her. Mr. Howey, of the men's furnishings department, is an expert hockey player. We have no doubt he will be a valuable acquisition to the store's team. Mr. C. Stapells, house furnishings buyer, and Mr. Hewes are very busy these days supervising the draperies and furnishings for the palatial new Empire theatre. We have heard that a certain young lady on the third floor has lost her heart and is going to sign a life contract in the very near future. The A. and A. A. Concert Reveals Real Artists Another of those very enjoyable concerts which are staged periodically through the winter months by the Amusement and Athletic Association, was held in the "Hudsonia" dining room on Thursday evening, December 2nd, at which about 150 members and their friends were present. The association was again fortunate in hearing Mr. R. L. Bateman, who rendered "She Is Far from the Land" and, in response to a hearty encore, "For You Alone" was all that could be desired. Miss Kate Hamilton sang "Bird Songs" in which her beautiful voice was heard to very great advantage. Mrs. Roy Carbert sang Tosti's "Good Bye," and as an encore, "Angus MacDonald." Mr. Bert Crockett sang "There's Life in the Old Dog Yet," which was very much appreciated, he being vociferously encored. All the other artists are members of the staff and their songs were all rendered in admirable style. One exceptionally pleasing number was the duet, "Tenor and Baritone," Mr. T. A. Crockett's tenor and Mr. Digney's baritone voices blending in perfect harmony. Miss Edna Southen and Miss K. Riddle were two excellent sopranos, whilst Miss W. E. Crowther's sweet contralto voice has never been heard to greater advantage. Mr. T. A. Crockett and Mr. George Saunders have fine tenor voices, whilst Mr. G. Robert's deep bass was used with effect in "Out on the Deep." Mr. C. Digney was splendid in "Captain Mack" and later his rendering of "My Old Shako" was perfect. Miss Moore acted as accompanist throughout and in addition gave a duet in company, with her sister. One cannot speak too highly of Miss Moore's assistance, as she is always ready and willing to help in any way that will add to the enjoyment of the staff, whether it be as accompanist or soloist. Mr. P. A. Stone, president of the Amusement and Athletic Association, acted as chairman. Community Singing is Getting Results
Community singing for the staff, which was inaugurated at the Edmonton store, November 1st, 1920, is reported to be an unqualified success. The staff arrive at 8.45 a.m. and sing usually two songs before 8.55 a.m. bell sounds, when the covers are removed preparatory to the day's business. The initiative was taken by the Amusement and Athletic Association. The fact that it is still retaining the original interest proves that the all-important co-operation has been obtained; hence the success. Whilst it is impossible yet to gauge the full extent of the benefits derived from community singing, it may be said that the early morning "grouch" is dissipated, and that alone makes it worth while, as it leaves the staff in a happier frame of mind. This cannot but conduce to the betterment of the service afforded to customers. From community singing to a trained choir is but a step, since even the untrained singer gradually falls into and holds the time and rhythm of the piece being sung, so that from an untrained band of voices a perfectly functioning choir is created. This is the aim of the Edmonton Amusement and Athletic Association, and with a continuance of the staff's co-operation that end will be attained. The Ad. Man's Destiny Mr. Jack Prest was going home one night in the street car. It was late, and the man sitting next to him began to talk. "What business are you in?" he asked. "The advertising business," replied Jack. "Is that so? Well, well, I used to be in the advertising business myself. I gave it up though and went into the rag-and-old-bottle business. I was a sandwich man for the Empire Theatre for six months." "Say," and he leaned over confidentially, "Ain't it hard when the wind blows?"
CALGARY The Rank and File By F. R. REEVE The newspapers recently had much to say concerning the remarkable honors paid in England and France to the bodies of two unknown soldiers who fell on the battlefields. It was a nation's whole-hearted recognition of the fact that Victory was after all due to the efforts and self-sacrifice of the rank and file. In the scheme of life each one of us has a definite sphere to fill. Lest those who now constitute the rank and file in the service of the Company should be inclined to regard their positions with something of dissatisfaction, as being of no importance, I would have them take a lesson from the honors paid to these two unknown soldiers. Upon those who constitute the front rank, those who come in contact with the public, the whole success of this great Company depends. Behind you it is true, stretches a long line that reaches back from the junior buyer, through to the Governor himself, but the work accomplished by this wonderful organization does not reach its greatest success except through your co-operation. The transaction between a customer and salesperson is not just so much money changing hands for a certain article. It represents the crowning success of a long series of operations, that, through your hands as the H.B.C. representative, reaches the goal for which it was intended, an appreciative buying public. Upon the conduct of the rank and file—upon the impressions that are derived from your personality—is this Company judged. The courtesy, helpfulness and efficiency that are displayed by you are the greatest assets this Company has. To know and to realize that no matter what your position in the service of the Company may be, that the Company is absolutely depending on your efforts will be to create in you a greater desire for helpfulness and efficiency which cannot fail to mean greater success for yourself and Company too.
VANCOUVER Everybody Boost for Our 1921 Hockey Team It has been asked of the editor why there were not more attending the hockey games last winter, and why the H.B.C. employees were very backward in supporting their own team, being especially conspicuous by their absence. We've a dandy team this year, folks, and the boys sure would like some "rooters." Come along and bring your friends and the horn off the old Ford. Help the team make a name for themselves in the Commercial League. The following are the names of our players: W. E. Almas (Capt.) E. Herbert P. Timmins Chub Anderson R. M. Mair J. Gilroy J.C. Hamm J. McDonald J. D. Barber C. Boe We were very grieved to hear on December 10th of the death of Mr. Patterson, husband of Mrs. W. Patterson, cashier in our children's shoe department. We are also bereaved of one of our old employees, Mr. James Hallisy, who passed away at his home on December 10th. The deceased was on our night staff, and had been in the Company's employ since 1918. The army and Navy League Hall again witnessed a popular H.B.C. dance. Approximately 350 attended and tripped the light fantastic to the strains of Garden's orchestra. Mr. Skelly, chairman, and his competent committee had charge of the affair, which was carried off without a hitch to a very successful ending. Mr. Lockyer Elected President of Vancouver Exhibition Association
Holding their first meeting since taking office, the directors of the Vancouver Exhibition Association on Dec. 16th elected Mr. H. T. Lockyer, manager of the Hudson's Bay Company, Vancouver retail store, as president for the ensuing year.—Vancouver Province. Mr. W. W. Frazer, the popular buyer for china and glass, left for Europe in the interests of his section, early this month. Many laudatory remarks were overheard by Eastern and American tourists anent his last collection of lovely china. Mr. Frazer apparently knows where to get them. "Where do they get all these pretty patterns—there's not an ugly one among them"—exclaimed a lady from Ottawa recently, and went on to say she had never seen a better display in New York, Montreal or Toronto. But that's Mr. Frazer's secret. We wish him bon voyage and the best of luck this time. Miss A. K. Smith, too, buyer of notions, neckwear, laces, trimmings, hankies and fancy jewellery, has been chosen for a trip abroad after the airy fairy "nothings"—"the stuff that dreams are made of"—that are so dear to feminine hearts. Her return from Europe ladened with spoils will be looked forward to with interest by her constituency in Vancouver. You may be sure Miss Smith will not overlook any of the cute or smart little knick-knacks that are being shown in the marts over there, and we shall all have an opportunity to be more than ever up-to-date on her return. Vancouver is to be congratulated on having two buyers in whom the Company has so much faith and confidence as to entrust with this important foreign buying. The Tell-Tale Inventory A Vancouver bailiff went out to levy on the contents of a house. The inventory began in the attic and ended in the cellar. When the dining-room was reached the tally of furniture ran thus: One dining room table, oak. One set of chairs (6), oak. One sideboard, oak. Two bottles of whiskey, (full)! Then the word "full" was stricken over and replaced by "empty" and the inventory went on in a hand that struggled and lurched across the page, until it closed with: "One revolving door mat." Mr. Greer Gets a Regular Shower of Good Things By E. Bell Of the recent year end festivities enjoyed by Hudson's Bay employees perhaps none had more of the vivres and relish of the days of real sport than the banquet tendered Mr.
Greer by his staff in the display department. This event took place in the Barron Hotel to begin with and ended at a box party to the opera to witness the "Dance Shop." The menu of the dinner, which was enjoyed both wisely and well, gives some of the unlucky individuals who were not invited an appetizer even to read: Greer Soup Goose a la Greer Oyster Cocktail, Y.M.C.A. Celery a la Celestial Citizen Brussels Sprouts a la Lulu Island Fried Sweet Potatoes, Brunette Hot Toasted Rolls, Blonde Combination Salad a la Display French Pastry Translated Cake, Devilled Creme de Chaufroid Cafe d'Hots D'el (N.B.—S.O.S. Calgary. M. Laparique, please note. Can you beat it?) Having done full justice to these delectable viands the innocent occasion of so much mirth was next trotted to the opera, where his friends had taken the precaution to present him with a lorgnette or opera glass, we forget which. (Anyway it was not a monocle.) Notwithstanding, to the everlasting credit of the display department, they all turned up next morning on time and in the best of spirits. Old-Time Employees Visit the Store Among the guests of the Store last month were Mr. and Mrs. Alexander J. Baird, both old- time employees of the Company, who devoted a number of years of faithful service in the old store and two or three years in the new store. Mr. Baird was secretary to the general manager, Mr. Lockyer. In 1917, he went to Honolulu for a new field to conquer. He was there but a little while before he sent for his fiancee, Miss Beck, then the general manager's stenographer. As soon as she arrived in Honolulu they were married. Being accustomed to speculating and used to seeing money made out of land, Mr. Baird (in face of much opposition) bought a piece of land and built three cottages thereon—an investment which proved a good one and a money maker.
KAMLOOPS H.B.C. Kamloops Store Dates Back to 1812 Location Has Changed Several Times to Keep Pace With Growth of City By A.E. DODMAN The Company's store at Kamloops dates back to the year 1812 and it is therefore one of the oldest establishments at present existing in the stores department. The original location was some distance from the present store site, as, like all Western towns, the business centre has changed several times, and the Company found it necessary to change from time to time in order to keep pace with the natural growth of the city. The present premises were purchased and remodelled by the Company in 1911, and have a frontage of 75 feet on Victoria Street, extending 125 feet on Second Avenue with two entrances on Victoria and one on Second Avenue. The building consists of two stories and basement. In addition the Company also operates a wholesale and retail tobacco and candy business on rented premises situated at the corner of Victoria Street and Third Avenue. The business at Kamloops comprises eight departments—general dry goods, ladies' wear, men's furnishings, boots and shoes, crockery and hardware, house furnishing, groceries and tobaccos. Miss Brooke, of the grocery staff, resigned her position with the Company and was married on January 1st, 1921. She was presented with a travelling bag by the staff. We wish her all kinds of joy and happiness in her new venture. She was a real "good fellow" and will be greatly missed by us. Miss Muir has accepted the position made vacant by Miss Brooke of the Grocery Department. We wish Miss Muir every success. Miss Cozens says she was never "locked out" in her life, but she experienced the feeling of being "locked in." She says "never again." The Staff presented Mr. A.E. Dodman, our store manager, and Mrs. Dodman with a Christmas gift of a very handsome tea set with best wishes. A rumour is heard to the effect that Mr. McDonald, the accountant, has become an expert dancer, and has accepted an invitation to teach three ladies the fine points in dancing. Nice for Mac, but kind of tough on the ladies.
After a very busy and most successful Christmas trade the staff have settled down for the most successful January sale we have ever had.
VERNON Entire Staff a Santa Claus to Mr. Pout, Xmas On Christmas Eve, at the close of the biggest day in the history of the Vernon Store, the staff gathered for a few minutes to extend good wishes and exchange tokens of friendship. At the conclusion, Mr. Pout was captured when trying to tip-toe off, set securely within the smiling circle, and compelled to listen to the following effusion which Tom Bone, the store poet, says he did not compose. It is now being blamed on Jack Ricketts, and so far Jack hasn't denied it.
Our dear respected Mister Pout We guess you guess what we're about; If not, you won't be long in doubt, But get the sense, So we shall quickly put to rout Your dread suspense. It's Christmas time, as you well know, And we have gathered here to show That years may come and years may go, With rush and zest, But our good feelings far outgrow This timely test? It gives us joy to give to you This coffee service, bright and new, And wish that all things good and true That hope conjures, May travel all the next year through With you and yours. Mr. Pout was too full for words (honi soit qui mal y pense), but he managed to express his hearty thanks for the splendid support and co-operation he had received from the entire staff during the Christmas rush, also for the kind thought which prompted the giving of such a beautiful gift. The coffee pot was one of those long narrow "prohibition" coffee pots that you are unable to tell what is inside of until you taste the contents. Tom Harrison struck up "He's a Jolly Good Fellow." "Arry" thought it was "Auld Lang Syne" and started off on his own, while James Henderson, in an endeavour to put them both right, commenced "Will You No Come Back Again." When the company broke up, those three were still at it, and nobody could tell which was winning.—R.W. Miss Cridland, treasurer of our Sisters' Sewing Circle, has been absent from the meeting several week. We were surprised to see her at the last meeting. She says her absence has been due to the fact that she had to attend "prayer meetings." We have since learned that a certain young man's "tin Lizzie" is being overhauled. May it take all winter —so Gladys will be at every meeting.
Miss Phillys Ripley, the girl with the sparkling eyes, assisted for several weeks in the hardware department but is back once again at her old stand tying bows for the kiddies. Her eyes still sparkle and there are many beaus waiting for her to cast her spell on one of them so that two may be tied into one bow. "Wonderful how popular some men are," said Watson, when he heard what happened Christmas Eve. The girls in the dry goods department placed mistletoe on the light over Mr. Andrews' desk—and not one missed him, even Mabel had hers. Nuff sed. Mr. Tom Bone, assistant manager of the grocery department, the staff poet, has changed his vocation and now spends his evenings making musical instruments. We wonder if it will be jazz or operatic music. We are glad to learn that Mrs. Griffin, wife of C. Griffin of the men's department, is home once again after being confined to the Hospital several weeks with typhoid fever. We all wish her a speedy recovery. Vernon, Gem of the Okanagan —and the H.B.C. Store, One of Its Institutions Thirty years ago, there were only two stores in Vernon, The Hudson's Bay Company and W.F. Cameron, both firms carrying a general line of merchandise. The only other stores in the Okanagan Valley, at this period, were one at Enderby, Landsdowne, Okanagan Mission and Penticton, so that these stores supplied the necessities of life practically to the whole of the Okanagan Valley, reaching from Sicamous to fifty miles beyond Penticton and from Grand Prairie to the White Valley district. The towns of Armstrong and Kelowna, at this period, were not in existence. Travelling in the early days was by stage and boat in Summer, the boat running from Sicamous to Enderby, thence by stage to Vernon, and the only method of travelling in Winter was by stage or pack horse. Mail, also, was received by these means of transportation. The great bulk of trading, at that time, was done with Victoria, which was a greater commercial centre than Vancouver. All merchandise from the Coast was carried by freight trains to Sicamous, transferred there to a small steamer as far as Enderby and thence by wagon to Vernon. Business conditions and the manner of trading in the early days were entirely different to the present day method. There were no banks in the Valley, all banking being done through Vancouver, cheques often passing around as currency and would have as many as a dozen endorsations before reaching the bank. Yearly credit was the system of trading. Farmers, ranchers, trappers and Indians paid their accounts once a year after they had received money for their crops and catch of furs; the amusing feature in regard to the credit in these days being that the average customer would ask of his account, simply looking at the total and settling up without checking up. Considerable business was done in the bulk, tea sold by the chest, flour and sugar by the ton, and other commodities in similar large quantities.
Welcome to our website – the perfect destination for book lovers and knowledge seekers. We believe that every book holds a new world, offering opportunities for learning, discovery, and personal growth. That’s why we are dedicated to bringing you a diverse collection of books, ranging from classic literature and specialized publications to self-development guides and children's books. More than just a book-buying platform, we strive to be a bridge connecting you with timeless cultural and intellectual values. With an elegant, user-friendly interface and a smart search system, you can quickly find the books that best suit your interests. Additionally, our special promotions and home delivery services help you save time and fully enjoy the joy of reading. Join us on a journey of knowledge exploration, passion nurturing, and personal growth every day! ebookbell.com

More Related Content

Similar to Javaserver Faces Introduction By Example Juneau Josh (20)

PDF
Jsf tutorial
Edress Oryakhail
 
PDF
Beginning Java with WebSphere Expert s Voice in Java Janson Robert W
kuclermialee
 
ODP
EmbbededGF@JavaOneHyd
Prasad Subramanian
 
PPT
Selenium-Browser-Based-Automated-Testing-for-Grails-Apps
chrisb206 chrisb206
 
PPTX
Survey of restful web services frameworks
Vijay Prasad Gupta
 
PPT
Lecture 19 dynamic web - java - part 1
Д. Ганаа
 
PPT
Spring hibernate tutorial
Rohit Jagtap
 
PDF
Servlet and jsp development with eclipse wtp
odilodif
 
PPT
Developing Java Web Applications
hchen1
 
PPTX
Jdbc
BindhuBhargaviTalasi
 
PPTX
Java script Basic
Jaya Kumari
 
ODP
Glass Fish Slides Fy2009 2
Abhishek Gupta
 
ODP
Glass Fish Slides Fy2009 2
Abhishek Gupta
 
PPT
Testing Java Web Apps With Selenium
Marakana Inc.
 
PPTX
Java Training Ahmedabad , Introduction of java web development
NicheTech Com. Solutions Pvt. Ltd.
 
PPT
Introduction to the Servlet / JSP course
JavaEE Trainers
 
PPT
Lecture 19 - Dynamic Web - JAVA - Part 1.ppt
KalsoomTahir2
 
PDF
Jsp and servlet_netbeans-webapps
OPENLANE
 
DOCX
Html servlet example
rvpprash
 
PDF
Jfxpub binding
Jérémie Nguetsop Komolo
 
Jsf tutorial
Edress Oryakhail
 
Beginning Java with WebSphere Expert s Voice in Java Janson Robert W
kuclermialee
 
EmbbededGF@JavaOneHyd
Prasad Subramanian
 
Selenium-Browser-Based-Automated-Testing-for-Grails-Apps
chrisb206 chrisb206
 
Survey of restful web services frameworks
Vijay Prasad Gupta
 
Lecture 19 dynamic web - java - part 1
Д. Ганаа
 
Spring hibernate tutorial
Rohit Jagtap
 
Servlet and jsp development with eclipse wtp
odilodif
 
Developing Java Web Applications
hchen1
 
Jdbc
BindhuBhargaviTalasi
 
Java script Basic
Jaya Kumari
 
Glass Fish Slides Fy2009 2
Abhishek Gupta
 
Glass Fish Slides Fy2009 2
Abhishek Gupta
 
Testing Java Web Apps With Selenium
Marakana Inc.
 
Java Training Ahmedabad , Introduction of java web development
NicheTech Com. Solutions Pvt. Ltd.
 
Introduction to the Servlet / JSP course
JavaEE Trainers
 
Lecture 19 - Dynamic Web - JAVA - Part 1.ppt
KalsoomTahir2
 
Jsp and servlet_netbeans-webapps
OPENLANE
 
Html servlet example
rvpprash
 
Jfxpub binding
Jérémie Nguetsop Komolo
 

Recently uploaded (20)

PDF
The dynastic history of the Chahmana.pdf
PrachiSontakke5
 
PPTX
How to Manage Large Scrollbar in Odoo 18 POS
Celine George
 
PDF
Reconstruct, Restore, Reimagine: New Perspectives on Stoke Newington’s Histor...
History of Stoke Newington
 
PPTX
MENINGITIS: NURSING MANAGEMENT, BACTERIAL MENINGITIS, VIRAL MENINGITIS.pptx
PRADEEP ABOTHU
 
PDF
LAW OF CONTRACT ( 5 YEAR LLB & UNITARY LLB)- MODULE-3 - LEARN THROUGH PICTURE
APARNA T SHAIL KUMAR
 
PDF
The Constitution Review Committee (CRC) has released an updated schedule for ...
nservice241
 
PDF
Stokey: A Jewish Village by Rachel Kolsky
History of Stoke Newington
 
PDF
Dimensions of Societal Planning in Commonism
StefanMz
 
PPTX
How to Set Up Tags in Odoo 18 - Odoo Slides
Celine George
 
PDF
Knee Extensor Mechanism Injuries - Orthopedic Radiologic Imaging
Sean M. Fox
 
PPTX
Stereochemistry-Optical Isomerism in organic compoundsptx
Tarannum Nadaf-Mansuri
 
PDF
DIGESTION OF CARBOHYDRATES,PROTEINS,LIPIDS
raviralanaresh2
 
PPTX
How to Create a PDF Report in Odoo 18 - Odoo Slides
Celine George
 
PDF
Generative AI: it's STILL not a robot (CIJ Summer 2025)
Paul Bradshaw
 
PPTX
grade 5 lesson matatag ENGLISH 5_Q1_PPT_WEEK4.pptx
SireQuinn
 
PDF
The History of Phone Numbers in Stoke Newington by Billy Thomas
History of Stoke Newington
 
PDF
ARAL-Orientation_Morning-Session_Day-11.pdf
JoelVilloso1
 
PDF
community health nursing question paper 2.pdf
Prince kumar
 
PPTX
A PPT on Alfred Lord Tennyson's Ulysses.
Beena E S
 
PDF
Isharyanti-2025-Cross Language Communication in Indonesian Language
Neny Isharyanti
 
The dynastic history of the Chahmana.pdf
PrachiSontakke5
 
How to Manage Large Scrollbar in Odoo 18 POS
Celine George
 
Reconstruct, Restore, Reimagine: New Perspectives on Stoke Newington’s Histor...
History of Stoke Newington
 
MENINGITIS: NURSING MANAGEMENT, BACTERIAL MENINGITIS, VIRAL MENINGITIS.pptx
PRADEEP ABOTHU
 
LAW OF CONTRACT ( 5 YEAR LLB & UNITARY LLB)- MODULE-3 - LEARN THROUGH PICTURE
APARNA T SHAIL KUMAR
 
The Constitution Review Committee (CRC) has released an updated schedule for ...
nservice241
 
Stokey: A Jewish Village by Rachel Kolsky
History of Stoke Newington
 
Dimensions of Societal Planning in Commonism
StefanMz
 
How to Set Up Tags in Odoo 18 - Odoo Slides
Celine George
 
Knee Extensor Mechanism Injuries - Orthopedic Radiologic Imaging
Sean M. Fox
 
Stereochemistry-Optical Isomerism in organic compoundsptx
Tarannum Nadaf-Mansuri
 
DIGESTION OF CARBOHYDRATES,PROTEINS,LIPIDS
raviralanaresh2
 
How to Create a PDF Report in Odoo 18 - Odoo Slides
Celine George
 
Generative AI: it's STILL not a robot (CIJ Summer 2025)
Paul Bradshaw
 
grade 5 lesson matatag ENGLISH 5_Q1_PPT_WEEK4.pptx
SireQuinn
 
The History of Phone Numbers in Stoke Newington by Billy Thomas
History of Stoke Newington
 
ARAL-Orientation_Morning-Session_Day-11.pdf
JoelVilloso1
 
community health nursing question paper 2.pdf
Prince kumar
 
A PPT on Alfred Lord Tennyson's Ulysses.
Beena E S
 
Isharyanti-2025-Cross Language Communication in Indonesian Language
Neny Isharyanti
 
Ad

Javaserver Faces Introduction By Example Juneau Josh

  • 1. Javaserver Faces Introduction By Example Juneau Josh download https://ebookbell.com/product/javaserver-faces-introduction-by- example-juneau-josh-11704300 Explore and download more ebooks at ebookbell.com
  • 2. Here are some recommended products that we believe you will be interested in. You can click the link to download. Javaserver Faces Introduction By Example 1st Edition Josh Juneau Auth https://ebookbell.com/product/javaserver-faces-introduction-by- example-1st-edition-josh-juneau-auth-4971844 Javaserver Faces Introduction By Example Josh Juneau https://ebookbell.com/product/javaserver-faces-introduction-by- example-josh-juneau-5052840 Javaserver Faces In Action 1st Edition Kito D Mann https://ebookbell.com/product/javaserver-faces-in-action-1st-edition- kito-d-mann-5470692 Javaserver Faces The Complete Reference Complete Reference Series 1st Edition Chris Schalk https://ebookbell.com/product/javaserver-faces-the-complete-reference- complete-reference-series-1st-edition-chris-schalk-1877086
  • 3. Javaserver Faces 1st Hans Bergsten https://ebookbell.com/product/javaserver-faces-1st-hans- bergsten-917936 Core Javaserver Faces 2nd Ed David M Geary Cay S Horstmann https://ebookbell.com/product/core-javaserver-faces-2nd-ed-david-m- geary-cay-s-horstmann-4099476 Mastering Javaserver Faces 22 Illustrated Leonard Anghel https://ebookbell.com/product/mastering-javaserver- faces-22-illustrated-leonard-anghel-55587594 Mastering Javaserver Faces Bill Dudney Jonathan Lehr Bill Willis https://ebookbell.com/product/mastering-javaserver-faces-bill-dudney- jonathan-lehr-bill-willis-975282 Core Javaserver Faces Cay S Horstmann https://ebookbell.com/product/core-javaserver-faces-cay-s- horstmann-976172
  • 6. For your convenience Apress has placed some of the front matter material after the index. Please use the Bookmarks and Contents at a Glance links to access them.
  • 7. v Contents at a Glance About the Author ..............................................................................................................xvii Acknowledgments.............................................................................................................xix Chapter 1: Introduction to Servlets N ...................................................................................1 Chapter 2: JavaServer Pages N ..........................................................................................55 Chapter 3: The Basics of JavaServer Faces N ....................................................................99 Chapter 4: Facelets N ........................................................................................................163 Chapter 5: JavaServer Faces Standard Components N ....................................................205 Chapter 6: Advanced JavaServer Faces and Ajax N .........................................................261 Index.................................................................................................................................325
  • 8. 1 CHAPTER 1 Introduction to Servlets Java servlets were the first technology for producing dynamic Java web applications. Sun Microsystems released the first Java Servlet specification in 1997. Since then it has undergone tremendous change, making it more powerful and easing development more with each release. The 3.0 version was released as part of Java EE 6 in December 2009. Although not always used directly by Java web developers, servlets are at the base of all Java EE applications. Many developers use servlet frameworks such as Java Server Pages (JSP) and Java Server Faces (JSF), both of those technologies compile pages into Java servlets behind the scenes via the servlet container. That said, a fundamental knowledge of Java servlet technology is very useful for any Java web developer. Servlets are Java classes that conform to the Java Servlet API, which allows a Java class to respond to requests. Although servlets can respond to any type of request, they are most commonly written to respond to HTTP requests. A servlet must be deployed to a Java servlet container in order to become usable. The Servlet API provides a number of objects that are used to enable the functionality of a servlet within a web container. Such objects include the request and response objects, pageContext, and a great deal of others, and when these objects are used properly, they enable a Java servlet to perform just about any task a web-based application needs to perform. As mentioned, servlets can produce not only static content but also dynamic content. Since a servlet is written in Java, any valid Java code can be used within the body of the servlet class. This empowers Java servlets and allows them to interact with other Java classes, the web container, the underlying file server, and much more. This chapter will get you started developing and deploying servlets, and provide you with foundational knowledge to move forward with other servlet-based web frameworks In this chapter, you will learn how to install Oracle’s GlassFish application server, a robust servlet container, which will enable you to deploy sophisticated Java enterprise applications. You will be taught the basics of developing servlets, how to use them with client web sessions, and how to link a servlet to another application. All the while, you will learn to use standards from the latest release of the Java Servlet API (3.2), which modernizes servlet development and makes it much easier and more productive than in years past. Note N You can run the examples within this chapter by deploying the JSFByExample.war file (contained in the sources) to a local Java EE application server container such as GlassFish v4.x. You can also set up the NetBeans 8.x project entitled JSFByExample that is contained in the sources, build it, and deploy to GlassFish v4.x. Otherwise, you can run the examples in Chapter 1 stand-alone using the instructions provided in the section “Packaging, Compiling, and Deploying a Servlet”. If you deploy the JSFByExample.war file to a Java EE application server container, you can visit the following URL to load the examples for this chapter: http://localhost:8080/JSFByExample/faces/chapter01/index.xhtml.
  • 9. CHAPTER 1 N INTRODUCTION TO SERVLETS 2 Setting Up a Java Enterprise Environment You’ll need an environment in which to experiment with servlets, and then later with JavaServer Faces. Oracle’s GlassFish application server is a good choice, as it is the Java EE 7 Reference Impementation. It’s easy to set up, and the following example will get you started and ready to run all the subsequent examples in the book. Example To get started, ownload and install Oracle’s GlassFish application server from the GlassFish web site. The version used for this book is the open source edition, release 4.1, and it can be downloaded from http://glassfish.java.net/ in the “Download” section. Select the .zip or .tar.gz download format, and decompress the downloaded files within a directory on your workstation. I will refer to that directory as /JAVA_DEV/GlassFish. The GlassFish distribution comes prepackaged with a domain so that developers can get up and running quickly. Once the .zip file has been unpacked, you can start the domain by opening a command prompt or terminal and starting GlassFish using the following statement: /PATH_TO_GLASSFISH /GlassFish/bin/asadmin start-domain domain1 The domain will start, and it will be ready for use. You will see output from the server that looks similar to the following: Waiting for domain1 to start ............ Successfully started the domain : domain1 domain Location: /PATH_TO_GLASSFISH/glassfish/domains/domain1 Log File: /PATH_TO_GLASSFISH/glassfish/domains/domain1/logs/server.log Admin Port: 4848 Command start-domain executed successfully. Explanation The development of Java EE applications begins with a Java EE–compliant application server. A Java EE–compliant server contains all the essential components to provide a robust environment for deploying and hosting enterprise Java applications. The GlassFish application server is the industry standard for Java EE 7. As of GlassFish 4.0, there is only an open sourced distribution of the server available, meaning that it is not possible to purchase Oracle support for GlassFish. However, in a production environment, you may want to consider purchasing GlassFish 4.x support from a third-party organization so that technical support will be available if needed. An alternative is to utilize a commercially supported server that is Java EE 7 compliant, such as Oracle WebLogic 12.1.x. Installing GlassFish is easy. It consists of downloading an archive and uncompressing it on your development machine. Once you’ve completed this, the application server will make use of your locally installed Java development kit (JDK) when it is started. JDK 8 is supported for use with GlassFish as of release 4.1. For GlassFish 4.0, please use JDK 7. Once the server starts, you can open a browser and go to http://localhost:4848 to gain access to the GlassFish administrative console. Most Java EE developers who deploy on GlassFish use the administrative console often. The administrative console provides developers with the tools needed to deploy web applications, register databases with Java Naming and Directory Interface (JNDI), set up security realms for a domain, and do much more. You should take some time to become familiar with the administrative console because the more you know about it, the easier it will be to maintain your Java EE environment. Installing the GlassFish application server is the first step toward developing Java applications for the enterprise. While other applications servers such as JBoss WildFly, Apache TomEE, and WebLogic are very well adopted, GlassFish offers developers a solid environment that is suitable for production use and easy to learn. It also has the bonus of being an open source application server and the reference implementation for Java EE 7.
  • 10. CHAPTER 1 N INTRODUCTION TO SERVLETS 3 Developing Your First Servlet Web applications are based upon a series of web views or pages. There is often a requirement to develop a view that has the ability to include content that may change at any given time. For instance, you may be developing a view that contains stock data, and you may wish to have that data updated often. Servlets provide the ability to produce dynamic content, allowing server-side computations and processes to update the data in the servlet at will. Example Develop a Java servlet class, and compile it to run within a Java servlet container. In this example, a simple servlet is created that will display some dynamic content to the web page. The The following code is the servlet code that contains the functionality for the servlet:package org.javaserverfaces.chapter01; import java.io.IOException; import java.io.PrintWriter; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; /** * Simple Dynamic Servlet * @author juneau */ public class SimpleServlet extends HttpServlet { /** * Processes requests for both HTTP * <code>GET</code> and * <code>POST</code> methods. * * @param request servlet request * @param response servlet response * @throws ServletException if a servlet-specific error occurs * @throws IOException if an I/O error occurs */ protected void processRequest(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.setContentType("text/html;charset=UTF-8"); PrintWriter out = response.getWriter(); try { /* * TODO output your page here. You may use following sample code. */ out.println("<html>"); out.println("<head>"); out.println("<title>Servlet SimpleServlet</title>"); out.println("</head>"); out.println("<body>"); out.println("<h2>Servlet SimpleServlet at " + request.getContextPath() + "</h2>"); out.println("<br/>Welcome to JavaServer Faces: Introduction By Example!");
  • 11. CHAPTER 1 N INTRODUCTION TO SERVLETS 4 out.println("</body>"); out.println("</html>"); } finally { out.close(); } } // <editor-fold defaultstate="collapsed" desc="HttpServlet methods. Click on the + sign on the left to edit the code."> /** * Handles the HTTP * <code>GET</code> method. * * @param request servlet request * @param response servlet response * @throws ServletException if a servlet-specific error occurs * @throws IOException if an I/O error occurs */ @Override protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { processRequest(request, response); } /** * Handles the HTTP * <code>POST</code> method. * * @param request servlet request * @param response servlet response * @throws ServletException if a servlet-specific error occurs * @throws IOException if an I/O error occurs */ @Override protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { processRequest(request, response); } /** * Returns a short description of the servlet. * * @return a String containing servlet description */ @Override public String getServletInfo() { return "Short description"; }// </editor-fold> }
  • 12. CHAPTER 1 N INTRODUCTION TO SERVLETS 5 The following code is the web deployment descriptor. This file is required for application deployment to a servlet container. It contains the servlet configuration and mapping that maps the servlet to a URL. Later in this chapter, will learn how to omit the servlet configuration and mapping from the web.xml file to make servlet development, deployment, and maintenance easier. <?xml version="1.0"?> <web-app xmlns="http://java.sun.com/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" version="3.0"> <servlet> <servlet-name>SimpleServlet</servlet-name> <servlet-class>org.javaeeexamples.chapter1.example01_02.SimpleServlet</servlet-class> </servlet> <servlet-mapping> <servlet-name>SimpleServlet</servlet-name> <url-pattern>/SimpleServlet</url-pattern> </servlet-mapping> <welcome-file-list> <welcome-file> /SimpleServlet </welcome-file> </welcome-file-list> </web-app> Note N Many web applications use a page named index.html or index.xhtml as their welcome file. There is nothing wrong with doing that, and as a matter of fact, it is the correct thing to do. The use of /SimpleServlet as the welcome file in this example is to make it easier to follow for demonstration purposes. To compile the Java servlet, use the javac command-line utility. The following line was excerpted from the command line, and it compiles the SimpleServlet.java file into a class file. First, traverse into the directory containing the SimpleServlet.java file; then, execute the following: javac -cp /JAVA_DEV/GlassFish/glassfish/modules/javax.servlet-api.jar SimpleServlet.java Once the servlet code has been compiled into a Java class file, it is ready to package for deployment. Note N You may want to consider installing a Java integrated development environment (IDE) to increase your develop- ment productivity. There are several very good IDEs available to developers, so be sure to choose one that contains the features you find most important and useful for development. As the author of this book on Java EE 7, I recommend installing NetBeans 8.x or newer for development. NetBeans is an open source IDE that is maintained by Oracle, and it includes support for all the cutting-edge features that the Java industry has to offer, including EJB development with Java EE 7, JavaFX 8 support, and more.
  • 13. CHAPTER 1 N INTRODUCTION TO SERVLETS 6 Explanation Java servlets provide developers with the flexibility to design applications using a request-response programming model. Servlets play a key role in the development of service-oriented and web application development on the Java platform. Different types of servlets can be created, and each of them is geared toward providing different functionality. The first type is the GenericServlet, which provides services and functionality. The second type, HttpServlet, is a subclass of GenericServlet, and servlets of this type provide functionality and a response that uses HTTP. The solution to this example demonstrates the latter type of servlet because it displays a result for the user to see within a web browser. Servlets conform to a life cycle for processing requests and posting results. First, the Java servlet container calls the servlet’s constructor. The constructor of every servlet must take no arguments. Next, the container calls the servlet init method, which is responsible for initializing the servlet. Once the servlet has been initialized, it is ready for use. At that point, the servlet can begin processing. Each servlet contains a service method, which handles the requests being made and dispatches them to the appropriate methods for request handling. Implementing the service method is optional. Finally, the container calls the servlet’s destroy method, which takes care of finalizing the servlet and taking it out of service. Every servlet class must implement the javax.servlet.Servlet interface or extend another class that does. In the solution to this example, the servlet named SimpleServlet extends the HttpServlet class, which provides methods for handling HTTP processes. In this scenario, a browser client request is sent from the container to the servlet; then the servlet service method dispatches the HttpServletRequest object to the appropriate method provided by HttpServlet. Namely, the HttpServlet class provides the doGet, doPut, doPost, and doDelete methods for working with an HTTP request. The HttpServlet class is abstract, so it must be subclassed, and then an implementation can be provided for its methods. In the solution to this example, the doGet method is implemented, and the responsibility of processing is passed to the processRequest method, which writes a response to the browser using the PrintWriter. Table 1-1 describes each of the methods available to an HttpServlet. Table 1-1. HttpServlet Methods Method Name Description doGet Used to process HTTP GET requests. Input sent to the servlet must be included in the URL address. For example: ?myName=Josh&myBook=JSF. doPost Used to process HTTP POST requests. Input can be sent to the servlet within HTML form fields. doPut Used to process HTTP PUT requests. doDelete Used to process HTTP DELETE requests. doHead Used to process HTTP HEAD requests. doOptions Called by the container to allow OPTIONS request handling. doTrace Called by the container to handle TRACE requests. getLastModified Returns the time that the HttpServletRequest object was last modified. init Initializes the servlet. destroy Finalizes the servlet. getServletInfo Provides information regarding the servlet.
  • 14. CHAPTER 1 N INTRODUCTION TO SERVLETS 7 A servlet generally performs some processing within the implementation of its methods and then returns a response to the client. The HttpServletRequest object can be used to process arguments that are sent via the request. For instance, if an HTML form contains some input fields that are sent to the server, those fields would be contained within the HttpServletRequest object. The HttpServletResponse object is used to send responses to the client browser. Both the doGet and doPost methods within a servlet accept the same arguments, namely, the HttpServletRequest and HttpServletResponse objects. Note N The doGet method is used to intercept HTTP GET requests, and doPost is used to intercept HTTP POST requests. Generally, the doGet method is used to prepare a request before displaying for a client, and the doPost method is used to process a request and gather information from an HTML form. In the solution to this example, both the doGet and doPost methods pass the HttpServletRequest and HttpServletResponse objects to the processRequest method for further processing. The HttpServletResponse object is used to set the content type of the response and to obtain a handle on the PrintWriter object in the processRequest method. The following lines of code show how this is done, assuming that the identifier referencing the HttpServletResponse object is response: response.setContentType("text/html;charset=UTF-8"); PrintWriter out = response.getWriter(); A GenericServlet can be used for providing services to web applications. This type of servlet is oftentimes used for logging events because it implements the log method. A GenericServlet implements both the Servlet and ServletConfig interfaces, and to write a generic servlet, only the service method must be overridden. How to Package, Compile, and Deploy a Servlet Once a servlet has been developed (and compiled), it needs to be deployed to a servlet container before it can be used. After deployment to the server, the servlet needs to be mapped to a URL for invocation. Example Compile the sources, set up a deployable application, and copy the contents into the GlassFish deployment directory. From the command line, use the javac command to compile the sources. javac -cp /PATH_TO_GLASSFISH/GlassFish/glassfish/modules/javax.servlet-api.jar SimpleServlet.java After the class has been compiled, deploy it along with the web.xml deployment descriptor, conforming to the appropriate directory structure. In web.xml, declare the servlet, and map it to a URL using the following format: <servlet> <servlet-name>SimpleServlet</servlet-name> <servlet-class>org.javaserverfaces.chapter01.SimpleServlet</servlet-class> </servlet> </servlet-mapping> <servlet-mapping> <servlet-name>SimpleServlet</servlet-name> <url-pattern>/SimpleServlet</url-pattern> </servlet-mapping>
  • 15. CHAPTER 1 N INTRODUCTION TO SERVLETS 8 QUICK START FOR DEPLOYING WITHOUT AN IDE To quickly get started with packaging, compiling, and deploying the example application for the servlet examples in this chapter on GlassFish or other servlet containers such as Apache Tomcat without an IDE, follow these steps: 1. Create a single application named SimpleServlet by making a directory named SimpleServlet. 2. Create a directory at the root of the application, and name it WEB-INF. Create an XML file in the new WEB-INF directory, and name it web.xml. In the web.xml, add the following markup: <?xml version="1.0" encoding="UTF-8"?> <web-app version="3.1" xmlns="http://xmlns.jcp.org/xml/ns/javaee" xmlns:xsi=" http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://xmlns.jcp.org/ xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd"> <servlet> <servlet-name>SimpleServlet</servlet-name> <servlet-class>org.javaserverfaces.chapter01.SimpleServlet</servlet-class> </servlet> <servlet-mapping> <servlet-name>SimpleServlet</servlet-name> <url-pattern>/SimpleServlet</url-pattern> </servlet-mapping> <session-config> <session-timeout> 30 </session-timeout> </session-config> </web-app> 3. Create “classes”, and “lib” drectories inside the directory that was created in step 2. Drag the Chapter 1 sources into the WEB-INF/classes directory. 4. Set your CLASSSPATH to include any necessary JAR files. For this chapter, the JavaMail API JAR (mail.jar) is required. Place it into the WEB-INF/lib directory and set your CLASSPATH accordingly. 5. At the command prompt, change directories so that you are within the “classes” directory that was created in Step 3. Compile each class within the org.javaserverfaces. chapter01 directory with the following command: javac orgjavaserverfaceschapter01*.java 6. Copy your SimpleServlet application into the /JAVA_DEV/GlassFish/glassfish/domains/ domain1/autodeploy directory for GlassFish, or the /Tomcat/webapps directory for Tomcat. Test the application by launching a browser and going to http://localhost:8080/SimpleServlet/servlet_ name, where servlet_name corresponds to the servlet name in each example. If using Tomcat, you may need to restart the server in order for the application to deploy.
  • 16. CHAPTER 1 N INTRODUCTION TO SERVLETS 9 Explanation To compile the sources, you can use your favorite Java IDE such as NetBeans or Eclipse, or you can use the command line. For the purposes of this example, I will use the command line. Note that in many of the remaining examples for this book, the NetBeans IDE is used. If you’re using the command line, you must ensure you are using the javac command that is associated with the same Java release that you will be using to run your servlet container. In this example we will assume that GlassFish 4.1 is being used with JDK 7, and therefore assume that the location of the Java SE 7 installation is at the following path: /Library/Java/JavaVirtualMachines/1.7.0.jdk/Contents/Home This path may differ in your environment if you are using a different operating system and/or installation location. To ensure you are using the Java runtime that is located at this path, set the JAVA_HOME environment variable equal to this path. On OS X and *nix operating systems, you can set the environment variable by opening the terminal and typing the following: export JAVA_HOME=/Library/Java/JavaVirtualMachines/1.7.0.jdk/Contents/Home If you are using Windows, use the SET command within the command line to set up the JAVA_HOME environment variable. set JAVA_HOME=C:your-java-se-path Next, compile your Java servlet sources, and be sure to include the javax.servlet-api.jar file that is packaged with your servlet container (use servlet-api.jar for Tomcat) in your CLASSPATH. You can set the CLASSPATH by using the –cp flag of the javac command. The following command should be executed at the command line from within the same directory that contains the sources. In this case, the source file is named SimpleServlet.java. javac -cp /path_to_jar/javax.servlet-api.jar SimpleServlet.java Next, package your application by creating a directory and naming it after your application. In this case, create a directory and name it SimpleServlet. Within that directory, create another directory named WEB-INF. Traverse into the WEB-INF directory, and create another directory named classes. Lastly, create directories within the classes directory in order to replicate your Java servlet package structure. For this example, the SimpleServlet.java class resides within the Java package org.javaserverfaces.chapter01, so create a directory for each of those packages within the classes directory. Create another directory within WEB-INF and name it lib; any JAR files containing external libraries should be placed within the lib directory. In the end, your directory structure should resemble the following: SimpleServlet |_WEB-INF |_classes |_org |_javaserverfaces |_chapter01 |_lib Place your web.xml deployment descriptor within the WEB-INF directory, and place the compiled SimpleServlet.class file within the chapter01 directory. The entire contents of the SimpleServlet directory can now be copied within the deployment directory for your application server container to deploy the application. Restart the application server if using Tomcat, and visit the URL http://localhost:8080/SimpleServlet/ SimpleServlet to see the servlet in action.
  • 17. CHAPTER 1 N INTRODUCTION TO SERVLETS 10 Registering Servlets Without WEB-XML Registering servlets in the web.xml file is cumbersome. With the later releases of the Servlet specification, it is possible to deploy servlets without the requirement for a web.xml file. In this section, we will take a look at how to register servlets without the web.xml requirement. Example Use the @WebServlet annotation to register the servlet, and omit the web.xml registration. This will alleviate the need to modify the web.xml file each time a servlet is added to your application. The following adaptation of the SimpleServlet class that was used in the previous example includes the @WebServlet annotation and demonstrates its use: package org.javaserverfaces.chapter01; import java.io.IOException; import java.io.PrintWriter; import javax.servlet.ServletException; import javax.servlet.annotation.WebServlet; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; /** * Registering Servlets without WEB-XML * @author juneau */ @WebServlet(name = "SimpleServletNoDescriptor", urlPatterns = {"/SimpleServletNoDescriptor"}) public class SimpleServletNoDescriptor extends HttpServlet { /** * Processes requests for both HTTP * <code>GET</code> and * <code>POST</code> methods. * * @param request servlet request * @param response servlet response * @throws ServletException if a servlet-specific error occurs * @throws IOException if an I/O error occurs */ protected void processRequest(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.setContentType("text/html;charset=UTF-8"); PrintWriter out = response.getWriter(); try { /* * TODO output your page here. You may use following sample code. */ out.println("<html>"); out.println("<head>"); out.println("<title>Servlet SimpleServlet</title>");
  • 18. CHAPTER 1 N INTRODUCTION TO SERVLETS 11 out.println("</head>"); out.println("<body>"); out.println("<h2>Servlet SimpleServlet at " + request.getContextPath() + "</h2>"); out.println("<br/>Look ma, no WEB-XML!"); out.println("</body>"); out.println("</html>"); } finally { out.close(); } } /** * Handles the HTTP <code>GET</code> method. * * @param request servlet request * @param response servlet response * @throws ServletException if a servlet-specific error occurs * @throws IOException if an I/O error occurs */ @Override protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { processRequest(request, response); } /** * Handles the HTTP <code>POST</code> method. * * @param request servlet request * @param response servlet response * @throws ServletException if a servlet-specific error occurs * @throws IOException if an I/O error occurs */ @Override protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { processRequest(request, response); } } In the end, the servlet will be accessible via a URL in the same way that it would if the servlet were registered within web.xml. Explanation There are a couple of ways to register servlets with a web container. The first way is to register them using the web.xml deployment descriptor, as demonstrated earlier in the chapter. The second way to register them is to use the @WebServlet annotation. The Servlet 3.0 API introduced the @WebServlet annotation, which provides an easier technique to use for mapping a servlet to a URL. The @WebServlet annotation is placed before the declaration of a class, and it accepts the elements listed in Table 1-2.
  • 19. CHAPTER 1 N INTRODUCTION TO SERVLETS 12 In the solution to this example, the @WebServlet annotation maps the servlet class named SimpleServletNoDescriptor to the URL pattern of /SimpleServletNoDescriptor, and it also names the servlet SimpleServletNoDescriptor. @WebServlet(name="SimpleServletNoDescriptor", urlPatterns={"/SimpleServletNoDescriptor"}) The new @WebServlet can be used rather than altering the web.xml file to register each servlet in an application. This provides ease of development and manageability. However, in some cases, it may make sense to continue using the deployment descriptor for servlet registration, such as if you do not want to recompile sources when a URL pattern changes. If you look at the web.xml file used earlier, you can see the following lines of XML, which map the servlet to a given URL and provide a name for the servlet. These lines of XML perform essentially the same function as the @WebServlet annotation in this example. <servlet> <servlet-name>SimpleServletNoDescriptor</servlet-name> <servlet-class>org.javaserverfaces.chapter01.SimpleServletNoDescriptor</servlet-class> </servlet> <servlet-mapping> <servlet-name>SimpleServletNoDescriptor</servlet-name> <url-pattern>/SimpleServletNoDescriptor</url-pattern> </servlet-mapping> Displaying Dynamic Content with a Servlet As mentioned previously in the chapter, it sometimes makes sense to deliver dynamic content (content that changes frequently), rather than serving static content that never changes. In this example, we will take a look at how to develop a servlet that has the ability to display dynamic content. Table 1-2. @WebServlet Annotation Elements Element Description description Description of the servlet displayName The display name of the servlet initParams Accepts list of @WebInitParam annotations largeIcon The large icon of the servlet loadOnStartup Load on start-up order of the servlet name Servlet name smallIcon The small icon of the servlet urlPatterns URL patterns that invoke the servlet
  • 20. CHAPTER 1 N INTRODUCTION TO SERVLETS 13 Example Define a field within your servlet to contain the dynamic content that is to be displayed. Post the dynamic content on the page by appending the field containing it using the PrintWriter println method. The following example servlet declares a Date field and updates it with the current Date each time the page is loaded: package org.javaserverfaces.chapter01; import java.io.IOException; import java.io.PrintWriter; import java.util.Date; import javax.servlet.ServletException; import javax.servlet.annotation.WebServlet; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; /** * Displaying Dynamic Content with a Servlet * * @author juneau */ @WebServlet(name = "CurrentDateAndTime", urlPatterns = {"/CurrentDateAndTime"}) public class CurrentDateAndTime extends HttpServlet { /** * Processes requests for both HTTP <code>GET</code> and <code>POST</code> * methods. * * @param request servlet request * @param response servlet response * @throws ServletException if a servlet-specific error occurs * @throws IOException if an I/O error occurs */ protected void processRequest(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.setContentType("text/html;charset=UTF-8"); PrintWriter out = response.getWriter(); try { out.println("<html>"); out.println("<head>"); out.println("<title>Servlet CurrentDateAndTime</title>"); out.println("</head>"); out.println("<body>"); out.println("<h1>Servlet CurrentDateAndTime at " + request.getContextPath() + "</h1>"); out.println("<br/>"); Date currDateAndTime = new Date(); out.println("The current date and time is: " + currDateAndTime);
  • 21. CHAPTER 1 N INTRODUCTION TO SERVLETS 14 out.println("</body>"); out.println("</html>"); } finally { out.close(); } } /** * Handles the HTTP <code>GET</code> method. * * @param request servlet request * @param response servlet response * @throws ServletException if a servlet-specific error occurs * @throws IOException if an I/O error occurs */ @Override protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { processRequest(request, response); } /** * Handles the HTTP <code>POST</code> method. * * @param request servlet request * @param response servlet response * @throws ServletException if a servlet-specific error occurs * @throws IOException if an I/O error occurs */ @Override protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { processRequest(request, response); } } The resulting output from this servlet will be the current date and time. Explanation One of the reasons why Java servlets are so useful is because they allow dynamic content to be displayed on a web page. The content can be taken from the server itself, a database, another web site, or many other web-accessible resources. Servlets are not static web pages; they are dynamic, and that is arguably their biggest strength. In the solution to this example, a servlet is used to display the current time and date on the server. When the servlet is processed, the doGet method is called, which subsequently makes a call to the processRequest method, passing the request and response objects. Therefore, the processRequest method is where the bulk of the work occurs. The processRequest method creates a PrintWriter by calling the response.getWriter method, and the PrintWriter is used to display content on the resulting web page. Next, the current date and time are obtained from the server by creating a new Date and assigning it to the currDateAndTime field. Lastly, the processRequest method sends the web content through the out.println method, and the contents of the currDateAndTime field are concatenated to a String and sent to out.println as well. Each time the servlet is processed, it will display the current date and time at the time in which the servlet is invoked because a new Date is created with each request.
  • 22. CHAPTER 1 N INTRODUCTION TO SERVLETS 15 This example just scratches the surface of what is possible with a Java servlet. Although displaying the current date and time is trivial, you could alter that logic to display the contents of any field contained within the servlet. Whether it be an int field that displays a calculation that was performed by the servlet container or a String field containing some information, the possibilities are endless. Handling Requests and Responses Most applications allow forms that accept input, and then produce a response. This is one of the main components of an HTTP application, and servlets are ideal for handling a request-response lifecycle. It can also be useful to develop forms in HTML, and have the form submitted to a processing engine, such as a servlet. Example To see a request-response example in action, create a standard HTML-based web form, and when the submit button is clicked, invoke a servlet to process the end-user input and post a response. To examine this technique, you will see two different pieces of code. The following code is HTML that is used to generate the input form. Pay particular attention to the <form> and <input> tags. You will see that the form’s action parameter lists a servlet name, MathServlet. <html> <head> <title>Simple Math Servlet</title> </head> <body> <h1>This is a simple Math Servlet</h1> <form method="POST" action="MathServlet"> <label for="numa">Enter Number A: </label> <input type="text" id="numa" name="numa"/><br><br> <label for="numb">Enter Number B: </label> <input type="text" id="numb" name="numb"/><br/><br/> <input type="submit" value="Submit Form"/> <input type="reset" value="Reset Form"/> </form> </body> </html> Next, take a look at the following code for a servlet named MathServlet. This is the Java code that receives the input from the HTML code listed earlier, processes it accordingly, and posts a response. package org.javaserverfaces.chapter01; import java.io.IOException; import java.io.PrintWriter; import java.util.Date; import javax.servlet.*; import javax.servlet.annotation.WebServlet; import javax.servlet.http.*;
  • 23. CHAPTER 1 N INTRODUCTION TO SERVLETS 16 /** * Handling Requests and Responses */ // Uncomment the following line to run example stand-alone //@WebServlet(name="SessionServlet", urlPatterns={"/MathServlet"}) // The following will allow the example to run within the context of the JSFByExample example // enterprise application (JSFByExample.war distro or Netbeans Project) @WebServlet(name = "MathServlet", urlPatterns = {"/chapter01/MathServlet"}) public class MathServlet extends HttpServlet { public void doPost(HttpServletRequest req, HttpServletResponse res) throws IOException, ServletException { res.setContentType("text/html"); // Store the input parameter values into Strings String numA = req.getParameter("numa"); String numB = req.getParameter("numb"); PrintWriter out = res.getWriter(); out.println("<html><head>"); out.println("<title>Test Math Servlet</title>"); out.println("t<style>body { font-family: 'Lucida Grande', " + "'Lucida Sans Unicode';font-size: 13px; }</style>"); out.println("</head>"); out.println("<body>"); try { int solution = Integer.valueOf(numA) + Integer.valueOf(numB); /* * Display some response to the user */ out.println("<p>Solution: " + numA + " + " + numB + " = " + solution + "</p>"); } catch (java.lang.NumberFormatException ex) { // Display error if an exception is raised out.println("<p>Please use numbers only...try again.</p>"); } out.println("</body></html>"); out.close(); } }
  • 24. CHAPTER 1 N INTRODUCTION TO SERVLETS 17 Note N To run the example, deploy the JSFByExample application to your application server container, and then enter the following address into your browser: http://localhost:8080/JSFByExample/chapter01/math.html. This assumes you are using default port numbers for your application server installation. If using the NetBeans project that was packaged with the sources, you do not need to worry about copying the code as everything is pre-configured. Explanation Servlets make it easy to create web applications that adhere to a request and response life cycle. They have the ability to provide HTTP responses and also process business logic within the same body of code. The ability to process business logic makes servlets much more powerful than standard HTML code. The solution to this example demonstrates a standard servlet structure for processing requests and sending responses. An HTML web form contains parameters that are sent to a servlet. The servlet then processes those parameters in some fashion and publishes a response that can be seen by the client. In the case of an HttpServlet object, the client is a web browser, and the response is a web page. Values can be obtained from an HTML form by using HTML <input> tags embedded within an HTML <form>. In the solution to this example, two values are accepted as input, and they are referenced by their id attributes as numa and numb. There are two more <input> tags within the form; one of them is used to submit the values to the form action, and the other is used to reset the form fields to blank. The form action is the name of the servlet that the form values will be passed to as parameters. In this case, the action is set to MathServlet. The <form> tag also accepts a form-processing method, either GET or POST. In the example, the POST method is used because form data is being sent to the action; in this case, data is being sent to MathServlet. You could, of course, create an HTML form as detailed as you would like and then have that data sent to any servlet in the same manner. This example is relatively basic; it serves to give you an understanding of how the processing is performed. The <form> action attribute states that the MathServlet should be used to process the values that are contained within the form. The MathServlet name is mapped back to the MathServlet class via the web.xml deployment descriptor or the @WebServlet annotation. Looking at the MathServlet code, you can see that a doPost method is implemented to handle the processing of the POST form values. The doPost method accepts HttpServletRequest and HttpServletResponse objects as arguments. The values contained with the HTML form are embodied within the HttpServletRequest object. To obtain those values, call the request object’s getParameter method, passing the id of the input parameter you want to obtain. In this example, those values are obtained and stored within local String fields. String numA = req.getParameter("numa"); String numB = req.getParameter("numb"); Once the values are obtained, they can be processed as needed. In this case, those String values are converted into int values, and then they are added together to generate a sum and stored into an int field. That field is then presented as a response on a resulting web page. int solution = Integer.valueOf(numA) + Integer.valueOf(numB); As mentioned, the HTML form could be much more complex, containing any number of <input> fields. Likewise, the servlet could perform more complex processing of those field values. This example is merely the tip of the iceberg, and the possibilities are without bounds. Servlet-based web frameworks such as Java Server Pages and Java Server Faces hide many of the complexities of passing form values to a servlet and processing a response. However, the same basic framework is used behind the scenes.
  • 25. CHAPTER 1 N INTRODUCTION TO SERVLETS 18 Listening for Servlet Container Events There are cases when it may be useful for an application to perform some tasks when it is being started up or shut down. In such cases, servlet context event listeners can become useful. Example Create a servlet context event listener to alert when the application has started up or when it has been shut down. The following solution demonstrates the code for a context listener, which will log application start-up and shutdown events and send e-mail alerting of such events: package org.javaserverfaces.chapter01; import java.util.Properties; import javax.mail.Message; import javax.mail.Session; import javax.mail.Transport; import javax.mail.internet.InternetAddress; import javax.mail.internet.MimeMessage; import javax.servlet.ServletContextListener; import javax.servlet.ServletContextEvent; import javax.servlet.annotation.WebListener; @WebListener public class StartupShutdownListener implements ServletContextListener { @Override public void contextInitialized(ServletContextEvent event) { System.out.println("Servlet startup..."); System.out.println(event.getServletContext().getServerInfo()); System.out.println(System.currentTimeMillis()); sendEmail("Servlet context has initialized"); } @Override public void contextDestroyed(ServletContextEvent event) { System.out.println("Servlet shutdown..."); System.out.println(event.getServletContext().getServerInfo()); System.out.println(System.currentTimeMillis()); // See error in server.log file if mail is unsuccessful sendEmail("Servlet context has been destroyed..."); } /** * This implementation uses the GMail smtp server * @param message * @return */
  • 26. CHAPTER 1 N INTRODUCTION TO SERVLETS 19 private boolean sendEmail(String message) { boolean result = false; String smtpHost = "smtp.gmail.com"; String smtpUsername = "username"; String smtpPassword = "password"; String from = "fromaddress"; String to = "toaddress"; int smtpPort = 587; System.out.println("sending email..."); try { // Send email here //Set the host smtp address Properties props = new Properties(); props.put("mail.smtp.host", smtpHost); props.put("mail.smtp.auth", "true"); props.put("mail.smtp.starttls.enable", "true"); // create some properties and get the default Session Session session = Session.getInstance(props); // create a message Message msg = new MimeMessage(session); // set the from and to address InternetAddress addressFrom = new InternetAddress(from); msg.setFrom(addressFrom); InternetAddress[] address = new InternetAddress[1]; address[0] = new InternetAddress(to); msg.setRecipients(Message.RecipientType.TO, address); msg.setSubject("Servlet container shutting down"); // Append Footer msg.setContent(message, "text/plain"); Transport transport = session.getTransport("smtp"); transport.connect(smtpHost, smtpPort, smtpUsername, smtpPassword); Transport.send(msg); result = true; } catch (javax.mail.MessagingException ex) { ex.printStackTrace(); result = false; } return result; } } Note N To run this example, you may need additional external JARs in your CLASSPATH. Specifically, make sure you have mail.jar and javaee.jar.
  • 27. CHAPTER 1 N INTRODUCTION TO SERVLETS 20 Explanation Sometimes it is useful to know when certain events occur within the application server container. This concept can be useful under many different circumstances, but most often it would likely be used for initializing an application upon start-up or cleaning up after an application upon shutdown. A servlet listener can be registered with an application to indicate when it has been started up or shut down. Therefore, by listening for such events, the servlet has the opportunity to perform some actions when they occur. To create a listener that performs actions based upon a container event, you must develop a class that implements the ServletContextListener interface. The methods that need to be implemented are contextInitialized and contextDestroyed. Both of the methods accept a ServletContextEvent as an argument, and they are automatically called each time the servlet container is initialized or shut down, respectively. To register the listener with the container, you can use one of the following techniques: Utilize the u @WebListener annotation, as demonstrated by the solution to this example. Register the listener within the u web.xml application deployment descriptor. Use the u addListener methods defined on ServletContext. For example, to register this listener within web.xml, you would need to add the following lines of XML: <listener> <listener-class> org.javaserverfaces.chapter01.StartupShutdownListener</listener-class> </listener> Neither way is better than the other. The only time that listener registration within the application deployment descriptor (web.xml) would be more helpful is if you had the need to disable the listener in some cases. On the other hand, to disable a listener when it is registered using @WebListener, you must remove the annotation and recompile the code. Altering the web deployment descriptor does not require any code to be recompiled. There are many different listener types, and the interface that the class implements is what determines the listener type. For instance, in this example, the class implements the ServletContextListener interface. Doing so creates a listener for servlet context events. If, however, the class implements HttpSessionListener, it would be a listener for HTTP session events. The following is a complete listing of listener interfaces: javax.servlet.ServletRequestListener javax.servlet.ServletRequestAttrbiteListener javax.servlet.ServletContextListener javax.servlet.ServletContextAttributeListener javax.servlet.HttpSessionListener javax.servlet.HttpSessionAttributeListener It is also possible to create a listener that implements multiple listener interfaces. To learn more about listening for different situations such as attribute changes, please see the section entitled Listening for Attribute Changes. Setting Initialization Parameters It is possible to set initialization parameters for servlets as well. Doing so can be handy in cases where you would like to implement a task with default values if none were given.
  • 28. CHAPTER 1 N INTRODUCTION TO SERVLETS 21 Example #1 Set the servlet initialization parameters using the @WebInitParam annotation. The following code sets an initialization parameter that is equal to a String value: package org.javaserverfaces.chapter01; import java.io.IOException; import java.io.PrintWriter; import javax.servlet.*; import javax.servlet.annotation.WebInitParam; import javax.servlet.annotation.WebServlet; import javax.servlet.http.*; @WebServlet(name="SimpleServletCtx1", urlPatterns={"/SimpleServletCtx1"}, initParams={ @WebInitParam(name="name", value="Duke") }) public class SimpleServletCtx1 extends HttpServlet { @Override public void doGet(HttpServletRequest req, HttpServletResponse res) throws IOException, ServletException { res.setContentType("text/html"); PrintWriter out = res.getWriter(); /* Display some response to the user */ out.println("<html><head>"); out.println("<title>Simple Servlet Context Example</title>"); out.println("t<style>body { font-family: 'Lucida Grande', " + "'Lucida Sans Unicode';font-size: 13px; }</style>"); out.println("</head>"); out.println("<body>"); out.println("<p>This is a simple servlet to demonstrate context! Hello " + getServletConfig().getInitParameter("name") + "</p>"); out.println("</body></html>"); out.close(); } } To execute the example using the sources for this book, load the following URL into your web browser: http://localhost:8080/JSFByExample/SimpleServletCtx1. The resulting web page will display the following text: This is a simple servlet to demonstrate context! Hello Duke
  • 29. CHAPTER 1 N INTRODUCTION TO SERVLETS 22 Example #2 Place the init parameters inside the web.xml deployment descriptor file. The following lines are excerpted from the web.xml deployment descriptor for the SimpleServlet application. They include the initialization parameter names and values. <web-app> <servlet> <servlet-name>SimpleServletCtx1</servlet-name> <servlet-class> org.javaserverfaces.chapter01.SimpleServletCtx1</servlet-class> <init-param> <param-name>name</param-name> <param-value>Duke</param-value> </init-param> ... </servlet> ... </web-app> Explanation Oftentimes there is a requirement to set initialization parameters for a servlet in order to initialize certain values. Servlets can accept any number of initialization parameters, and there are a couple of ways in which they can be set. The first example is to annotate the servlet class with the @WebInitParam annotation, and the second way to set an initialization parameter is to declare the parameter within the web.xml deployment descriptor, as demonstrated in the second example. Either way will work; however, the solution using @WebInitParam is based upon the newer Java Servlet 3.0 API. Therefore, Example #1 is the more contemporary approach, but Example #2 remains valid for following an older model or using an older Java servlet release. To use the @WebInitParam annotation, it must be embedded within the @WebServlet annotation. Therefore, the servlet must be registered with the web application via the @WebServlet annotation rather than within the web.xml file. For more information on registering a servlet via the @WebServlet annotation, see the section entitled Registering Servlets Without web.xml. The @WebInitParam annotation accepts a name-value pair as an initialization parameter. In the solution to this example, the parameter name is name, and the value is Duke. @WebInitParam(name="name", value="Duke") Once set, the parameter can be used within code by calling getServletConfig().getInitializationParameter() and passing the name of the parameter, as shown in the following line of code: out.println("<p>This is a simple servlet to demonstrate context! Hello " + getServletConfig().getInitParameter("name") + "</p>"); The annotations have the benefit of providing ease of development, and they also make it easier to maintain servlets as a single package rather than jumping back and forth between the servlet and the deployment descriptor. However, those benefits come at the cost of compilation because in order to change the value of an initialization parameter using the @WebInitParam annotation, you must recompile the code. Such is not the case when using the web.xml deployment descriptor. It is best to evaluate your application circumstances before committing to a standard for naming initialization parameters.
  • 30. CHAPTER 1 N INTRODUCTION TO SERVLETS 23 Filtering Web Requests Another useful technique can be to apply a filter against a specified URL for a servlet. A filter can then invoke custom processing each time the URL is visited, and the filter will be executed prior to the servlet. Example Create a servlet filter that will be processed when the specified URL format is used to access the application. In this example, the filter will be executed when a URL conforming to the format of /* is used. This format pertains to any URL in the application. Therefore, any page will cause the servlet to be invoked. package org.javaserverfaces.chapter01; import java.io.IOException; import java.io.PrintWriter; import java.util.Date; import javax.servlet.*; import javax.servlet.annotation.WebFilter; import javax.servlet.http.*; /** * This filter obtains the IP address of the remote host and logs * it. * * @author juneau */ @WebFilter("/*") public class LoggingFilter implements Filter { private FilterConfig filterConf = null; public void init(FilterConfig filterConf) { this.filterConf = filterConf; } public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException { String userAddy = request.getRemoteHost(); filterConf.getServletContext().log("Vistor User IP: " + userAddy); chain.doFilter(request, response); } @Override public void destroy() { throw new UnsupportedOperationException("Not supported yet."); } }
  • 31. CHAPTER 1 N INTRODUCTION TO SERVLETS 24 The filter could contain any processing; the important thing to note is that this servlet is processed when a specified URL is used to access the application. Note N To invoke the filter, load a URL for the application with which the filter is associated. For the purposes of this example, load the following URL (for the previous example) to see the filter add text to the server log: http://localhost:8080/JSFByExample/SimpleServletCtx1. How It Works Web filters are useful for preprocessing requests and invoking certain functionality when a given URL is visited. Rather than invoking a servlet that exists at a given URL directly, any filter that contains the same URL pattern will be invoked prior to the servlet. This can be helpful in many situations, perhaps the most useful for performing logging, authentication, or other services that occur in the background without user interaction. Filters must implement the javax.servlet.Filter interface. Methods contained within this interface include init, destroy, and doFilter. The init and destroy methods are invoked by the container. The doFilter method is used to implement tasks for the filter class. As you can see from this example, the filter class has access to the ServletRequest and ServletResponse objects. This means the request can be captured, and information can be obtained from it. This also means the request can be modified if need be. For example, including the user name in the request after an authentication filter has been used. If you want to chain filters or if more than one filter exists for a given URL pattern, they will be invoked in the order in which they are configured in the web.xml deployment descriptor. It is best to manually configure the filters if you are using more than one per URL pattern rather than using the @WebFilter annotation. To manually configure the web.xml file to include a filter, use the <filter> and <filter-mapping> XML elements along with their associated child element tags. The following excerpt from a web.xml configuration file shows how the filter that has been created for this example may be manually configured within the web.xml file: <filter> <filter-name>LoggingFilter</filter-name> <filter-class>LoggingFilter</filter-class> </filter> <filter-mapping> <filter-name>LogingFilter</filter-name> <url-pattern>/*</url-pattern> </filter-mapping> Of course, the @WebFilter annotation takes care of the configuration for you, so in this case the manual configuration is not required. Note N As of Servlet 3.1 API, if a filter invokes the next entity in the chain, each of the filter service methods must run in the same thread as all filters that apply to the servlet.
  • 32. CHAPTER 1 N INTRODUCTION TO SERVLETS 25 Listening for Attribute Changes Servlets can perform listening event tasks when HTTP session attributes are changed by implementing the HttpSessionAttributeListener interface. Example This example demonstrates how to generate an attribute listener servlet to listen for such events as attributes being added, removed, or modified. The following class demonstrates this technique by implementing HttpSessionAttributeListener and listening for attributes that are added, removed, or replaced within the HTTP session: package org.javaserverfaces.chapter01; import javax.servlet.ServletContext; import javax.servlet.ServletContextEvent; import javax.servlet.ServletContextListener; import javax.servlet.annotation.WebListener; import javax.servlet.http.HttpSession; import javax.servlet.http.HttpSessionAttributeListener; import javax.servlet.http.HttpSessionBindingEvent; /** * Attribute Listener */ @WebListener public final class AttributeListener implements ServletContextListener, HttpSessionAttributeListener { private ServletContext context = null; @Override public void attributeAdded(HttpSessionBindingEvent se) { HttpSession session = se.getSession(); String id = session.getId(); String name = se.getName(); String value = (String) se.getValue(); String message = new StringBuffer("New attribute has been added to session: n"). append("Attribute Name: ").append(name).append("n").append("Attribute Value:"). append(value).toString(); log(message); } /** * * @param se */ @Override public void attributeRemoved(HttpSessionBindingEvent se) { HttpSession session = se.getSession(); String id = session.getId();
  • 33. CHAPTER 1 N INTRODUCTION TO SERVLETS 26 String name = se.getName(); if (name == null) { name = "Unknown"; } String value = (String) se.getValue(); String message = new StringBuffer("Attribute has been removed: n") .append("Attribute Name: ").append(name).append("n").append("Attribute Value:") .append(value).toString(); log(message); } @Override public void attributeReplaced(HttpSessionBindingEvent se) { String name = se.getName(); if (name == null) { name = "Unknown"; } String value = (String) se.getValue(); String message = new StringBuffer("Attribute has been replaced: n ").append(name). toString(); log(message); } private void log(String message) { if (context != null) { context.log("SessionListener: " + message); } else { System.out.println("SessionListener: " + message); } } @Override public void contextInitialized(ServletContextEvent event) { this.context = event.getServletContext(); log("contextInitialized()"); } @Override public void contextDestroyed(ServletContextEvent event) { // Do something } } Messages will be displayed within the server log file indicating when attributes have been added, removed, or replaced.
  • 34. CHAPTER 1 N INTRODUCTION TO SERVLETS 27 Explanation In some situations, it can be useful to know when an attribute has been set or what an attribute value has been set to. This example demonstrates how to create an attribute listener in order to determine this information. To create a servlet listener, you must implement one or more of the servlet listener interfaces. To listen for HTTP session attribute changes, implement HttpSessionAttributeListener. In doing so, the listener will implement the attributeAdded, attributeRemoved, and attributeReplaced methods. Each of these methods accepts HttpSessionBindingEvent as an argument, and their implementation defines what will occur when an HTTP session attribute is added, removed, or changed, respectively. In this example, you can see that each of the three methods listed in the previous paragraph contains a similar implementation. Within each method, the HttpSessionBindingEvent is interrogated and broken down into String values, which represent the ID, name, and value of the attribute that caused the listener to react. For instance, in the attributeAdded method, the session is obtained from HttpSessionBindingEvent, and then the session ID is retrieved from that via the use of getSession. The attribute information can be obtained directly from the HttpSessionBindingEvent using the getId and getName methods, as shown in the following lines of code: HttpSession session = se.getSession(); String id = session.getId(); String name = se.getName(); String value = (String) se.getValue(); After these values are obtained, the application can do whatever it needs to do with them. In this example, the attribute ID, name, and session ID are simply logged and printed. String message = new StringBuffer("New attribute has been added to session: n") .append("Attribute Name: ").append(name).append("n") .append("Attribute Value:").append(value).toString(); log(message); The body of the attributeReplaced and attributeRemoved methods contain similar functionality. In the end, the same routine is used within each to obtain the attribute name and value, and then something is done with those values. A few different options can be used to register the listener with the container. The @WebListener annotation is the easiest way to do so, and the only downfall to using it is that you will need to recompile code in order to remove the listener annotation if you ever need to do so. The listener can be registered within the web deployment descriptor, or it can be registered using one of the addListener methods contained in ServletContext. Although the example does not perform any life-changing events, it does demonstrate how to create and use an attribute listener. In the real world, such a listener could become handy if an application needed to capture the user name of everyone who logs in or needed to send an e-mail whenever a specified attribute is set. Applying a Listener to a Session In the same way that a listener can be applied to an HTTP session to listen for attribute changes, a listener can be applied for performing tasks when sessions are created and destroyedAssume in the following example that you wish to listen for sessions to be created so that you can count how many active sessions your application currently contains, as well as perform some initialization for each session.
  • 35. CHAPTER 1 N INTRODUCTION TO SERVLETS 28 Example Create a session listener, and implement the sessionCreated and sessionDestroyed methods accordingly. In the following example, a servlet is used to keep track of active sessions. Each time someone works with the application, a counter has one added to it. Likewise, each time a person leaves the application, then the counter goes down by one. package org.javaserverfaces.chapter01; import javax.servlet.annotation.WebListener; import javax.servlet.http.HttpSession; import javax.servlet.http.HttpSessionEvent; import javax.servlet.http.HttpSessionListener; /** * Applying a Session Listener * * @author juneau */ @WebListener public class SessionListener implements HttpSessionListener { private int numberOfSessions; public SessionListener() { numberOfSessions = 0; } public int getNumberOfSessions() { return numberOfSessions; } @Override public void sessionCreated(HttpSessionEvent arg) { HttpSession session = arg.getSession(); session.setMaxInactiveInterval(60); session.setAttribute("testAttr", "testVal"); synchronized (this) { numberOfSessions++; } System.out.println("Session created, current count: " + numberOfSessions); } @Override public void sessionDestroyed(HttpSessionEvent arg) { HttpSession session = arg.getSession(); synchronized (this) { numberOfSessions--; } System.out.println("Session destroyed, current count: " + numberOfSessions); System.out.println("The attribute value: " + session.getAttribute(("testAttr"))); } }
  • 36. CHAPTER 1 N INTRODUCTION TO SERVLETS 29 Each time a new visitor visits the application, a new session is started, and testAttr is set. When the session times out, then it will be destroyed, and any attributes that have been set for the session will be removed. Explanation A meaningful way to track web application users is to place values in their HttpSession object. Using a Java servlet, session attributes can be set, which will exist for the life of the HttpSession. Once the session is invalidated, the attributes will be removed. To set up a session listener, create a Java servlet, annotate it with the @WebListener annotation, and implement javax.servlet.http.HttpSessionListener. Doing so will force the implementation of both the sessionCreated and sessionDestroyed methods, which is where the session magic occurs. In this example, the sessionCreated method first obtains a handle on the current HttpSession object by calling the HttpSessionEvent object’s getSession method. The handle is assigned to an HttpSession variable named session. Now that you have that variable initialized with the session object, it can be used to set the time of life and place attributes that will live and die with the session’s life. The first session configuration performed in the example is to set the maximum inactive life to 60 (seconds), after which time the servlet container will invalidate the session. Next an attribute named testAttr is set in the session and given a value of testVal. HttpSession session = arg.getSession(); session.setMaxInactiveInterval(60); session.setAttribute("testAttr", "testVal"); A field within the servlet named numberOfSessions is declared, and it is incremented each time a new session is started. Following the session.setAttribute() call, the counter is incremented within a synchronized statement. Finally, a message is printed to the server log indicating that a new session was created and providing the total active session count. Note N Placing the increment within the synchronized statement helps avoid concurrency issues with the field. For more information on Java synchronization and concurrency, please see the online documentation at http://docs.oracle.com/javase/tutorial/essential/concurrency/locksync.html. The sessionDestroyed method is called on a session once the maximum number of inactive seconds has passed. In this example, the method will be called after 60 seconds of inactivity. Within the sessionDestroyed method, another synchronization statement decrements the numberOfSessions field value by one, and then a couple of lines are printed to the server log indicating that a session has been destroyed and providing the new total number of active sessions. Session listeners can be used to set cookies and perform other useful tactics to help manage a user’s experience. They are easy to use and very powerful. Managing Session Attributes It is possible to maintain information throughout the life of an individual session. Servlets can make use of session attributes to retain information on a per-session basis. That information can then be used at any time, so long as the session remains available.
  • 37. CHAPTER 1 N INTRODUCTION TO SERVLETS 30 Example Make use of session attributes to retain session-based information. To do so, use the HttpServletRequest object to obtain access to the session, and then use the getAttribute() and setAttribute() methods accordingly to set information into the session. In the following scenario, an HTML page is used to capture a user’s e-mail address, and then the e-mail address is placed into a session attribute. The attribute is then used by Java servlets across different pages of the application in order to maintain state. The following code demonstrates what the HTML form (chapter01/sessionAttributeDemo.html) may look like in this scenario: <html> <head> <title></title> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> </head> <body> <h1>Provide an email address to use with this transaction</h1> <br/> <form method="POST" action="SessionServlet"> <input type="text" id="email" name="email"/> <br/> <input type="submit" value="Submit"/> </form> </body> </html> Next, the Java servlet named SessionServlet using a URL pattern of /SessionServlet is initiated when the form is submitted. Any form input values are passed to SessionServlet and processed accordingly. package org.javaserverfaces.chapter01; import java.io.*; import javax.servlet.*; import javax.servlet.annotation.WebServlet; import javax.servlet.http.*; // Uncomment the following line to run example stand-alone //@WebServlet(name="SessionServlet", urlPatterns={"/SessionServlet"}) // The following will allow the example to run within the context of the JSFByExample example // enterprise application (JSFByExample.war distro or Netbeans Project) @WebServlet(name="SessionServlet", urlPatterns={"/chapter01/SessionServlet"}) public class SessionServlet extends HttpServlet { public void doPost (HttpServletRequest req, HttpServletResponse res) throws ServletException, IOException { // Obtain he Session object HttpSession session = req.getSession(true);
  • 38. CHAPTER 1 N INTRODUCTION TO SERVLETS 31 // Set up a session attribute String email = (String) session.getAttribute ("session.email"); if (email == null) { email = req.getParameter("email"); session.setAttribute ("session.email", email); } String sessionId = session.getId(); res.setContentType("text/html"); PrintWriter out = res.getWriter(); out.println("<html>"); out.println("<head><title>Working with sessions</title></head>"); out.println("<body>"); out.println("<h1>Session Test</h1>"); out.println ("Your email address is: " + email + "<br/><br/>"); out.println ("Your session id: " + sessionId); out.println("</body></html>"); } } In the end, the e-mail address that was entered within the original HTML form was captured and used throughout the different pages in the application. How It Works Since the beginning of web development, session attributes have been used to retain important information regarding a user’s session. This concept holds true when developing using Java servlets as well, and servlets make it easy to maintain attribute values. All HttpServlet classes must implement doGet or doPost methods in order to process web application events. In doing so, these methods have access to the HttpServletRequest object as it is passed to them as an argument. An HttpSession object can be gleaned from the HttpServletRequest, and therefore, it can be used to retrieve and set attributes as needed. In this example, an HTTP session attribute is used to store an e-mail address. That address is then used throughout the application within different servlet classes by obtaining the session object and then retrieving the attribute value. // Obtain the Session object HttpSession session = req.getSession(true); // Set up a session attribute String email = (String) session.getAttribute ("session.email"); if (email == null) { email = req.getParameter("email"); session.setAttribute ("session.email", email); } Any attributes will remain in the HttpSession object as long as the session remains valid. The session ID will remain consistent when traversing between pages. You can see that the solution to this example obtains and prints the current session ID for reference. Using attributes in the HttpSession is a good way to pass data around to maintain a session’s state.
  • 39. CHAPTER 1 N INTRODUCTION TO SERVLETS 32 Downloading a File Using a Servlet Servlet applications have the ability to download a given file using a series of InputStreams and OutputStreams. Example Write a servlet that will accept the name and path of a chosen file and then read the file and stream it to the file requestor. The following web page can be used to select a file for the servlet to download. Although the following HTML (chapter01/download.html) contains a statically typed file name, it could very well contain a dynamic list of files from a database or other source: <!DOCTYPE html> <html> <head> <title></title> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> </head> <body> <h1>Click on the link below to download the file.</h1> <br/> <a href="DownloadServlet?filename=downloadTest.txt">Download test file</a> <br/> </body> </html> Note N For the example, you can create and edit a file in your root directory next to the WEB-INF folder, and name the file downloadTest.txt to see the servlet transfer the data to your browser client. When a user clicks the link presented on the web page from the previous HTML, the following servlet will be used to download the given file by passing the HttpServletRequest and HttpServletResponse objects to it along with the file that should be downloaded: package org.javaserverfaces.chapter01; import java.io.DataInputStream; import java.io.File; import java.io.FileInputStream; import java.io.IOException; import java.io.InputStream; import java.io.PrintWriter; import javax.servlet.ServletContext; import javax.servlet.ServletException; import javax.servlet.ServletOutputStream; import javax.servlet.annotation.WebServlet; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse;
  • 40. CHAPTER 1 N INTRODUCTION TO SERVLETS 33 /** * * @author juneau */ // Uncomment the following line to run example stand-alone //@WebServlet(name = "DownloadServlet", urlPatterns = {"/DownloadServlet"}) // The following will allow the example to run within the context of the JSFByExample // enterprise application (JSFByExample.war distro or Netbeans Project) @WebServlet(name = "DownloadServlet", urlPatterns = {"/chapter01/DownloadServlet"}) public class DownloadServlet extends HttpServlet { /** * Handles the HTTP * <code>GET</code> method. * * @param request servlet request * @param response servlet response * @throws ServletException if a servlet-specific error occurs * @throws IOException if an I/O error occurs */ @Override protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { // Read parameter from form that contains the filename to download String fileToDownload = request.getParameter("filename"); // Call the download method with the given file System.err.println("Downloading file now..."); doDownload(request, response, fileToDownload); } /** * Sends a file to the output stream. * * @param req The request * @param resp The response * @param original_filename The name the browser should receive. */ private void doDownload( HttpServletRequest request, HttpServletResponse response, String originalFile) throws IOException { final int BYTES = 1024; int length = 0; ServletOutputStream outStream = response.getOutputStream(); ServletContext context = getServletConfig().getServletContext(); response.setContentType( (context.getMimeType( originalFile ) != null) ? context.getMimeType( originalFile ) : "text/plain" ); response.setHeader( "Content-Disposition", "attachment; filename="" + originalFile + """ );
  • 41. CHAPTER 1 N INTRODUCTION TO SERVLETS 34 InputStream in = context.getResourceAsStream("/" + originalFile); byte[] bbuf = new byte[BYTES]; while ((in != null) && ((length = in.read(bbuf)) != -1)) { outStream.write(bbuf,0,length); } outStream.flush(); outStream.close(); } /** * Returns a short description of the servlet. * * @return a String containing servlet description */ @Override public String getServletInfo() { return "Short description"; } } The servlet will not produce a response; it will simply download the given file to the end user when the user clicks the link to download the file. Explanation Downloading files is an essential task for almost any web application. Performing the steps that are provided by this example will make it easy to achieve this task. This example demonstrates an easy case in which users can visit a web page, click a file to download, and have the file retrieved from the server and copied to their machine. The HTML is very simplistic in this example, and it lists a URL link that invokes the servlet and passes the name of the file that is to be downloaded. When the user clicks the link, the name of the file is passed to /DownloadServlet as a parameter with the name filename. When the link is clicked, the servlet doGet method is invoked. The first task that is performed in the doGet method is to read the filename parameter from the invoking web page. That information is then passed to the doDownload method along with the HttpServletRequest and HttpServletResponse objects. In the doDownload method, the ServletOutputStream is obtained from the HttpServletResponse object, and the ServletContext is obtained for later use. To download a file, the servlet must provide a response of the same type that matches that of the file to be downloaded. It must also indicate in the response header that an attachment is to be included. Therefore, the first tasks to be performed by the doDownload method involve setting up the HttpServletResponse appropriately. response.setContentType( (context.getMimeType( originalFile ) != null) ? context.getMimeType( originalFile ) : "text/plain" ); response.setHeader( "Content-Disposition", "attachment; filename="" + originalFile + """ ); The file name, in this case originalFile, is used to obtain the MIME type of the file. If the MIME type of the file is null, then text/plain will be returned. The attachment is set up in the response header as well, by appending the file name as an attachment to the Content-Disposition. Next, the doDownload method obtains a reference to the file that is to be downloaded by calling the ServletContext getResourceAsStream method and passing the name of the file. This will return an InputStream object that can be used to read the contents of the indicated file. A byte buffer is then
  • 42. CHAPTER 1 N INTRODUCTION TO SERVLETS 35 created, which will be used to obtain chunks of data from the file when it is being read. The final real task is to read the file contents and copy them to the output stream. This is done using a while loop, which will continue to read from the InputStream until everything has been processed. Chunks of data are read in and written to the output stream using the loop. while ((in != null) && ((length = in.read(bbuf)) != -1)) { outStream.write(bbuf,0,length); } Lastly, the ServletOutputStream object’s flush method is called to clear the contents, and it is then closed to release resources. The magic of downloading files using a Java servlet may be a bit obfuscated by this example, however, because a static file is being used as the download source in this example. In real life, the HTML page would probably contain a list of files that are contained within a database or on a file system, and then when the user selects a file to download, the servlet will process that file accordingly, even extracting the file from the database if necessary. Dispatching Requests The concept of handing off tasks to other workers to perform action can be mirrored with real-world scenarios. If your car stops functioning properly, you take it to a mechanic. Servlet processing can follow a similar technique by handing off tasks to the appropriate worker servlets. This process is also known as dispatching. Furthermore, servlets have the ability to hand off tasks without redirecting the client to another site, and therefore, the URL in the browser does not change. Example To begin, create a request dispatcher servlet, which will decide which task needs to be completed and then send the request to an appropriate servlet to achieve that task. The following example demonstrates this concept via an HTML form that accepts two numbers from the user and allows the user to decide what type of mathematical evaluation should be performed by the server. The servlet processes the request by first determining which type of mathematical evaluation should be performed and then dispatching the request to the appropriate servlet to perform the task. The following HTML form accepts two numbers from the user and allows them to choose which type of math to perform against the numbers:<html> <head> <title></title> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> </head> <body> <h1>Request Dispatch Example</h1> <p>Perform a mathematical evaluation. Insert two numbers to be evaluated and then choose the type of evaluation to perform.</p> <form method="POST" action="MathDispatcher"> <label for="numa">Enter Number A: </label> <input type="text" id="numa" name="numa"/><br><br> <label for="numb">Enter Number B: </label> <input type="text" id="numb" name="numb"/><br/><br/> <select id="matheval" name="matheval"> <option value="add">Add the numbers</option> <option value="subtract">Subtract the numbers</option>
  • 43. CHAPTER 1 N INTRODUCTION TO SERVLETS 36 <option value="multiply">Multiply the numbers</option> <option value="divide">Divide the numbers</option> </select> <input type="submit" value="Submit Form"/> <input type="reset" value="Reset Form"/> </form> </body> </html> The next piece of code is the servlet that will dispatch requests accordingly depending upon the value of the matheval field: package org.javaserverfaces.chapter01; import java.io.IOException; import javax.servlet.RequestDispatcher; import javax.servlet.ServletContext; import javax.servlet.ServletException; import javax.servlet.ServletRequest; import javax.servlet.annotation.WebServlet; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; /** * * @author juneau */ // Uncomment the following line to run example stand-alone //@WebServlet(name = "MathDispatcher", urlPatterns = {"/MathDispatcher"}) // The following will allow the example to run within the context of the JSFByExample // enterprise application (JSFByExample.war distro or Netbeans Project) @WebServlet(name = "MathDispatcher", urlPatterns = {"/chapter01/MathDispatcher"}) public class MathDispatcher extends HttpServlet { /** * Handles the HTTP * <code>POST</code> method. * * @param request servlet request * @param response servlet response * @throws ServletException if a servlet-specific error occurs * @throws IOException if an I/O error occurs */ @Override protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { System.out.println("In the servlet...");
  • 44. CHAPTER 1 N INTRODUCTION TO SERVLETS 37 // Store the input parameter values into Strings String eval = request.getParameter("matheval"); ServletContext sc = getServletConfig().getServletContext(); RequestDispatcher rd = null; int evaluate = 0; int add = 0; int subtract = 1; int multiply = 2; int divide = 3; if(eval.equals("add")) evaluate = add; if (eval.equals("subtract")) evaluate = subtract; if (eval.equals("multiply")) evaluate = multiply; if(eval.equals("divide")){ evaluate = divide; } switch(evaluate){ case(0): rd = sc.getRequestDispatcher("/AddServlet"); rd.forward(request, response); break; case(1): rd = sc.getRequestDispatcher("/SubtractServlet"); rd.forward(request, response); break; case(2): rd = sc.getRequestDispatcher("/MultiplyServlet"); rd.forward(request, response); break; case(3): rd = sc.getRequestDispatcher("/DivideServlet"); rd.forward(request, response); break; } } /** * Returns a short description of the servlet. * * @return a String containing servlet description */ @Override public String getServletInfo() { return "Short description"; } }
  • 45. CHAPTER 1 N INTRODUCTION TO SERVLETS 38 Next is an example of one of the servlets that the request will be dispatched to. The following is the code for the AddServlet, which will add the two numbers and return the sum to the user: package org.javaserverfaces.chapter01; import java.io.IOException; import java.io.PrintWriter; import javax.servlet.ServletException; import javax.servlet.annotation.WebServlet; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; /** * * @author juneau */ // Uncomment the following line to run example stand-alone //@WebServlet(name = "AddServlet", urlPatterns = {"/AddServlet"}) // The following will allow the example to run within the context of the JSFByExample // enterprise application (JSFByExample.war distro or Netbeans Project @WebServlet(name = "AddServlet", urlPatterns = {"/chapter01/AddServlet"}) public class AddServlet extends HttpServlet { /** * Processes requests for both HTTP * <code>GET</code> and * <code>POST</code> methods. * * @param request servlet request * @param response servlet response * @throws ServletException if a servlet-specific error occurs * @throws IOException if an I/O error occurs */ protected void processRequest(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.setContentType("text/html;charset=UTF-8"); PrintWriter out = response.getWriter(); // Store the input parameter values into Strings String numA = request.getParameter("numa"); String numB = request.getParameter("numb"); int sum = Integer.valueOf(numA) + Integer.valueOf(numB); try { out.println("<html>"); out.println("<head>"); out.println("<title>The Sum of the Numbers</title>"); out.println("</head>"); out.println("<body>"); out.println("<h1>Sum: " + sum + "</h1>"); out.println("<br/>"); out.println("<a href=example01_14.html>Try Again</a>");
  • 46. CHAPTER 1 N INTRODUCTION TO SERVLETS 39 out.println("</body>"); out.println("</html>"); } finally { out.close(); } } /** * Handles the HTTP * <code>GET</code> method. * * @param request servlet request * @param response servlet response * @throws ServletException if a servlet-specific error occurs * @throws IOException if an I/O error occurs */ @Override protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { processRequest(request, response); } /** * Handles the HTTP * <code>POST</code> method. * * @param request servlet request * @param response servlet response * @throws ServletException if a servlet-specific error occurs * @throws IOException if an I/O error occurs */ @Override protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { processRequest(request, response); } /** * Returns a short description of the servlet. * * @return a String containing servlet description */ @Override public String getServletInfo() { return "Short description"; } } Each of the other servlets is very similar to AddServlet, except the mathematical evaluation is different. To see a full listing of the code, please take a look at the sources for this book.
  • 47. CHAPTER 1 N INTRODUCTION TO SERVLETS 40 Explanation Sometimes it is a good idea to hide the forwarding of requests from the end user. Other times it just makes sense to hand off a request from one servlet to another so that another type of processing can take place. These are just two examples of when it is handy to perform a request dispatch within a servlet. Forwarding a request versus dispatching a request is different because a forwarded request hands off the request on the client side, whereas a dispatched request hands off the request on the server side. The difference can be quite large since the end user has no idea of server-side dispatches, whereas the browser is redirected to a different URL when the request is forwarded on the client side. Dispatching requests is an easy task. The facilities for doing so are built right into the ServletContext, so once you obtain a reference to ServletContext, then you simply call the getRequestDispatcher method to obtain a RequestDispatcher object that can be used to dispatch the request. When calling the getRequestDispatcher method, pass a String containing the name of the servlet that you want to hand off the request to. You can actually obtain a RequestDisptacher object for any valid HTTP resource within the application by passing the appropriate URL for the resource in String format to the getRequestDispatcher method. Therefore, if you’d rather dispatch to a JSP or HTML page, you can do that as well. After a RequestDispatcher object has been obtained, invoke its forward method by passing the HttpServletRequest and HttpServletResponse objects to it. The forward method performs the task of handing off the request. rd = sc.getRequestDispatcher("/AddServlet"); rd.forward(request, response); In the case of this example, you can dispatch requests to different servlets in order to perform a specific task. Once handed off, the servlet that has obtained the request is responsible for providing the response to the client. In this case, the servlet returns the result of the specified mathematical evaluation. Redirecting to Another Application or Site In certain situations, it can be useful to redirect from a servlet to a different application on the same server or a different site altogether. Example Use the HttpServletResponse object’s sendRedirect() method to redirect from the servlet to another URL. In the following example, when a URL that matches the /redirect pattern is used, then the servlet will redirect the browser to another site: import java.io.IOException; import javax.servlet.*; import javax.servlet.annotation.WebServlet; import javax.servlet.http.*; @WebServlet(name="RedirectServlet", urlPatterns={"/redirect"}) public class RedirectServlet extends HttpServlet { @Override public void doGet(HttpServletRequest req, HttpServletResponse res)
  • 48. CHAPTER 1 N INTRODUCTION TO SERVLETS 41 throws IOException, ServletException { String site = "http://www.apress.com"; res.sendRedirect(site); } } In this example, the servlet will redirect to the www.apress.com web site. Explanation There are some cases in which a web application needs to redirect traffic to another site or URL within the same or another application. For such cases, the HttpServletResponse sendRedirect method can be of use. The sendRedirect method accepts a URL in String format and then redirects the web browser to the given URL. Given that sendRedirect accepts a String-based URL makes it easy to build dynamic URLs as well. For instance, some applications may redirect to a different URL based upon certain parameters that are passed from a user. Dynamic generation of a URL in such cases may look something like the following: String redirectUrl = null; If(parameter.equals("SOME STRING") redirectUrl = "/" + urlPathA; else redirectUrl = "/" + urlPathB; res.sendRedirect(redirectUrl); The sendRedirect() method can also come in handy for creating the control for web menus and other page items that can send web traffic to different locations. Note N This simple redirect, as opposed to servlet chaining, does not pass the HttpRequest object along to the target address. Utilizing Cookies Within the Browser Securely If an application must maintain state, it should be maintained in a secure manner. Cookies are oftentimes used to pass data around as a means of maintaining state. Servlets can safeguard cookies by marking them as HTTP only.
  • 49. CHAPTER 1 N INTRODUCTION TO SERVLETS 42 Example Use “HTTP only” browser cookies to save the state. In the following example, one servlet is used to place some session information into a cookie in the browser. Another servlet is then called, which reads the cookie information and displays it to the user. The following servlet demonstrates how to store a cookie in the browser using a Java servlet: package org.javaserverfaces.chapter01; import java.io.IOException; import java.io.PrintWriter; import javax.servlet.ServletException; import javax.servlet.annotation.WebServlet; import javax.servlet.http.Cookie; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; /** * Securing State within the Browser * @author juneau */ @WebServlet(name = "SetCookieServlet", urlPatterns = {"/SetCookieServlet"}) public class SetCookieServlet extends HttpServlet { protected void processRequest(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.setContentType("text/html;charset=UTF-8"); PrintWriter out = response.getWriter(); Cookie cookie = new Cookie("sessionId","12345"); cookie.setHttpOnly(true); cookie.setMaxAge(-30); response.addCookie(cookie); try { out.println("<html>"); out.println("<head>"); out.println("<title>SetCookieServlet</title>"); out.println("</head>"); out.println("<body>"); out.println("<h1>Servlet SetCookieServlet is setting a cookie into the browser</h1>"); out.println("<br/><br/>"); out.println("<a href='DisplayCookieServlet'>Display the cookie contents.</a>"); out.println("</body>"); out.println("</html>"); } finally { out.close(); } }
  • 50. CHAPTER 1 N INTRODUCTION TO SERVLETS 43 @Override protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { processRequest(request, response); } @Override protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { processRequest(request, response); } } The next code listing demonstrates a servlet that reads the cookies in the browser and prints out the contents: package org.javaserverfaces.chapter01; import java.io.IOException; import java.io.PrintWriter; import javax.servlet.ServletException; import javax.servlet.annotation.WebServlet; import javax.servlet.http.Cookie; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; /** * Securely Maintaining State within the Browser * @author juneau */ @WebServlet(name = "DisplayCookieServlet", urlPatterns = {"/DisplayCookieServlet"}) public class DisplayCookieServlet extends HttpServlet { protected void processRequest(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.setContentType("text/html;charset=UTF-8"); PrintWriter out = response.getWriter(); Cookie[] cookies = request.getCookies(); try { out.println("<html>"); out.println("<head>"); out.println("<title>Display Cookies</title>"); out.println("</head>"); out.println("<body>"); for(Cookie cookie:cookies){ out.println("<p>"); out.println("Cookie Name: " + cookie.getName()); out.println("<br/>"); out.println("Value: " + cookie.getValue()); out.println("</p>"); }
  • 51. CHAPTER 1 N INTRODUCTION TO SERVLETS 44 out.println("</body>"); out.println("</html>"); } finally { out.close(); } } @Override protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { processRequest(request, response); } @Override protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { processRequest(request, response); } } Explanation Using cookies to store data within the browser is a technique that has been in practice for years. Since Servlet 3.0 API, the ability to mark a cookie as HTTP only has become available. This allows the cookie to be safeguarded against client-side scripting attacks, making the cookie more secure. Any standard servlet can create a cookie and place it into the current session. Similarly, any servlet that is contained within the same session can read or update a session’s cookies values. In this example, two servlets are used to demonstrate how cookies work. The first servlet that is listed is responsible for creating a new cookie and setting it into the browser session. The second servlet is responsible for displaying the contents of the cookie to the user. To create a cookie, simply instantiate a new javax.servlet.http.Cookie object and assign a name and value to it. Passing both the name and value into the Cookie constructor at the time of instantiation can assign a name and value, or it can be done by passing values to the cookie’s setName and setValue methods. Once the cookie has been instantiated, properties can be set that will help to configure the cookie. In this example, the cookie’s setMaxAge and setHttpOnly methods are called, setting the time of life for the cookie and ensuring that it will be guarded against client-side scripting. For a complete listing of cookie properties, please refer to Table 1-3. Finally, the cookie is placed into the response by passing it to the response object’s addCookie method. Cookie cookie = new Cookie("sessionId","12345"); cookie.setHttpOnly(true); cookie.setMaxAge(-30); response.addCookie(cookie);
  • 52. CHAPTER 1 N INTRODUCTION TO SERVLETS 45 The second servlet, DisplayCookieServlet, is responsible for reading and displaying the session’s cookies values. When DisplayCookieServlet is invoked, its processRequest method is called, which obtains the cookies within the response object by calling response.getCookies() and setting the result to an array of Cookie objects. Cookie[] cookies = request.getCookies(); The cookie object array can now be iterated over in order to obtain each cookie and print out its contents. The servlet does so by using a for loop and printing out each cookie’s name and value. for(Cookie cookie:cookies){ out.println("<p>"); out.println("Cookie Name: " + cookie.getName()); out.println("<br/>"); out.println("Value: " + cookie.getValue()); out.println("</p>"); } Finalizing Servlet Tasks It is easy to perform cleanup tasks within the context of a servlet. Example To cleanup or perform finalization within a servlet, first provide code for performing any cleanup within the servlet destroy method. Second, in the case that there are potentially long-running methods, code them so that you will become aware of a shutdown and, if necessary, halt and return so that the servlet can shut down cleanly. The following code excerpt is a small example of a destroy method. In this code, it is being used to initialize local variables and is setting the beingDestroyed boolean value to indicate that the servlet is shutting down. Table 1-3. Cookie Property Methods Property Description setComment Sets a comment to describe the cookie. setDomain Specifies the domain in which the cookie belongs. setHttpOnly Marks the cookie as HTTP only. setMaxAge Sets the maximum lifetime of the cookie. A negative value indicates that the cookie will expire when the session ends. setPath Specifies a path for the cookie to which the client should return it. setSecure Indicates that the cookie should be sent only using a secure protocol. setValue Assigns a value to the cookie. setVersion Specifies the version of the cookie protocol that the cookie will comply with.
  • 53. CHAPTER 1 N INTRODUCTION TO SERVLETS 46 ... /** * Used to finalize the servlet */ public void destroy() { // Tell the servlet it is shutting down setBeingDestroyed(true); // Perform any cleanup thisString = null; } ... The code within the destroy method may successfully achieve a full cleanup of the servlet, but in the case where there may be a long-running task, then it must be notified of a shutdown. The following excerpt is a block of code that signifies a long-running task. The task should stop processing once the shutdown is indicated by the beingDestroyed value becoming true. for (int x = 0; (x <= 100000 && !isBeingDestroyed()); x++) { doSomething(); } Explanation The finalization of a servlet can be very important, especially if the servlet is using some resources that may lead to a memory leak, making use of a reusable resource such as a database connection or in order to persist some values for another session. In such cases, it is a good idea to perform cleanup within the servlet destroy method. Every servlet contains a destroy method (which may be implemented to overload default behavior) that is initiated once the servlet container determines that a servlet should be taken out of service. The destroy method is called once all of a servlet’s service methods have stopped running. However, if there is a long-running service method, then a server grace period can be set that would cause any running service to be shut down when the grace period is reached. As mentioned earlier, the destroy method is the perfect place to clean up resources. However, the destroy method is also a good place to help clean up after long-running services. Cleanup can be done by setting a servlet-specific local variable to indicate that the servlet is being destroyed and by having the long-running service check the state of that variable periodically. If the variable indicates that the destroy method has been called, then it should stop executing. Reading and Writing with Nonblocking I/O First generation web applications oftentimes were plagued with the user clicking a button to submit a request to perform a read or write operation, and then waiting for a period of time so that the task could complete. Sometimes this was a momentary wait, and other timesit was a longer wait. Modern implementations of the Servlet API make it possible to perform asynchronous I/O, helping to alleviate this issue. Example Use the Non-Blocking I/O API that is part of the Servlet 3.1 release to create an asynchronous solution. To use the new technology, implement the new ReadListener interface when performing nonblocking reads, and implement the WriteListener interface for performing nonblocking writes. The implementation class can then be registered to a ServletInputStream or ServletOutputStream so that reads or writes can be performed when the listener finds that servlet content can be read or written without blocking.
  • 54. CHAPTER 1 N INTRODUCTION TO SERVLETS 47 The following sources are those of a ReadListener implementation that reside in the source file org.javaserverfaces.chapter01.AcmeReadListenerImpl.java, and they demonstrate how to implement the ReadListener: package org.javaserverfaces.chapter01; import java.io.IOException; import java.util.logging.Level; import java.util.logging.Logger; import javax.servlet.AsyncContext; import javax.servlet.ReadListener; import javax.servlet.ServletInputStream; public class AcmeReadListenerImpl implements ReadListener { private ServletInputStream is = null; private AsyncContext async = null; public AcmeReadListenerImpl(ServletInputStream in, AsyncContext ac) { this.is = in; this.async = ac; System.out.println("read listener initialized"); } @Override public void onDataAvailable() { System.out.println("onDataAvailable"); try { StringBuilder sb = new StringBuilder(); int len = -1; byte b[] = new byte[1024]; while (is.isReady() && (len = is.read(b)) != -1) { String data = new String(b, 0, len); System.out.println(data); } } catch (IOException ex) { Logger.getLogger(AcmeReadListenerImpl.class.getName()).log(Level.SEVERE, null, ex); } } @Override public void onAllDataRead() { System.out.println("onAllDataRead"); async.complete(); }
  • 55. Other documents randomly have different content
  • 56. WHAT HAPPENED AT MOOSE FACTORY DURING SUMMER AND FALL, 1920 Extracts from the Post Journal from Entries by J. L. Gaudet, Post Manager July 1st—Our steamer, the "Inenew," left this morning on her first trip to Charlton Island, taking the District staff to the island for the summer, as this is our summer distributing point. Dr. Stewart and Rev. W. G. Walton were passengers. July 6th—The steamer returned with a cargo for Moose Factory of Charlton Depot stock. The steamer returned to Charlton with a load of lumber which I am shipping to the Straits. July 14th—The steamer returned with her second cargo from Charlton, and took another load of lumber for the Strait Posts. Mr. Johansen of the Biological Branch of the Naval Department of the Canadian Government, was a passenger on his way to Fort George. Mr. Fred McLeod and family were also passengers on their way to Woswonaby Post. Mr. McLeod is going there in the capacity of Post Manager. July 21st—Mr. F. D. Wilson arrived here to-day with two apprentice clerks, Messrs. Beveridge and Findlay, both from Aberdeen, Scotland. Aug. 3rd—Mr. Aurey, the government treaty paymaster, arrived here on his annual trip, paying treaty to the Indians. Mr. Aurey is assisted by Dr. Baker. Aug. 10th—Mr. Russell and family, Mr. John Louttit and family, arrived with the schooner "Fort George." These gentlemen are on their way out to civilization. Mr. Russell was in charge of Fort George Post. Aug. 14th—Mr. Romanet, general fur trade inspector, arrived here with Mrs. Romanet and two children. Mr. Romanet says he is here on an official visit from the Fur Trade Commissioner's Office. Inspector Phillips and Sgt. Joy, of the R.C.M. Police, also arrived to-day. They are on their way to the Belcher Islands to investigate some Eskimo murder case. Aug. 17th—A large seaplane, "The Caaz," with Capt. Maxwell as pilot and Mr. Doan as engineer, landed here this afternoon. This is the first flying machine to come to Moose Factory and was quite a sight for our Indians. Aug. 19th—The general inspector left on the schooner "Fort George" for Charlton Island this morning at 7 o'clock. A canoe carrying the ship's papers and two apprentice clerks, Mr. Gregory and Mr. Bremner, arrived at 1 p.m., just a few hours late to catch the schooner which I was holding for that purpose, so I had to get busy and send off our hay-boat with this mail to Charlton Island. Aug. 23rd—The seaplane landed here to-day on her second trip from Remy Lake, which is a few miles from Cochrane, with two moving picture men, Mr. Blake and Mr.
  • 57. Tash. They claim that they are being sent by the Ontario Government to take pictures. Aug. 26th—We had a visit from Capt. Mack to-day. He came with our schooner "Fort Charles" from Charlton Island, and states that they had a hard and trying trip coming through the Straits. Mr. and Mrs. Mayer were also passengers. Mr. Mayer is our worthy Post Manager at Great Whale River and is on his way out to civilization on a few months' leave. Aug. 27th—The seaplane "Caaz" brought us some newspapers from Cochrane, dated Aug. 25th, with the latest news. Aug. 31st—We have at last managed to extinguish the bush fire which was started by the Rev. Mr. Haythornthwaite on the 25th inst., after working day and night since it started. This will be quite a relief to the many families who are still camped across the river, as they were afraid to come back. Sept. 2nd—Our steamer "Inenew" landed here to-day with our District Manager, Mr. Rackham, Mr. Romanet, the general inspector, Mr. Griffith, manager of Albany Post, who is acting as private secretary to the general inspector, Messrs. Blake and Tash, movie men, and the Rev. Mr. Walton were passengers. The seaplane "Caaz" also arrived from Remy Lake with Mr. Griffin, representing the Toronto Star, as passenger. Sept. 21st—Mr. A. Nicolson and family arrived this evening from Rupert's House, after a hard and trying trip around the coast. Mr. Nicolson has been in the employ of the Hudson's Bay Company for forty years. It is with much regret that we see Mr. Nicolson severing his active services with the good old Company. Sept. 23rd—Mr. and Mrs. J. W. Anderson and child landed here to-day after spending a few months' holiday in civilization. Mr. Anderson is on his way to his Post, which is Attawapiskat. Oct. 1st—The steamer "Inenew" landed here to-day with the District Office staff and the balance of our outfit. This finishes our season's transport. Oct. 7th—Capt. G. R. Redfearn, A. Guibeau, engineer, Inspector Phillips, Sgt. Joy, Mr. Johansen and Mr. Sainsbury left this morning for Clute. Oct. 9th—Hauled out the S.S. "Inenew" to winter quarters and stored away the hauling gear. Oct. 27th—Packet canoes returned from the line to-day and by them received the first issue of our magazine, The Beaver. Oct. 29th—Mr. G. R. Ray, fur trade inspector, and Mr. J. B. Neil arrived here to-day at mid day. Nov. 10th—The river is frozen over, and hardly any snow on the ground as yet. We are having fine weather.—J. L. Gaudet, Post Manager.
  • 58. The Ghost is Foiled in Lac Seul's Haunted Room By R. O. OTTEN It was Christmas at Lac Seul Post, that historic place, well known to men of the North. Quite a number of the Outpost managers had come in to spend Christmas with the Post Manager and his family. The last to arrive was Mr. R. He had travelled over 200 miles by dog team and cariole to get there. After the hand-shaking was over, Mr. M., the Post Manager, drew Mr. R. aside and asked if he believed in ghosts. Mr. R. laughed and said he didn't believe in any kind of spirits, except the kind they used to have at Christmas in the old days, but wanted to know what the joke was. The Post Manager told him that he had only one room left vacant, and nobody had slept in that room for years as it was supposed to be haunted. The story was that on two different occasions at the usual Christmas gathering of the Outpost managers, there had been tragic endings to several guests who had occupied that room. Both had died from having their throats cut from ear to ear—and no one had slept there since. Mr. R. said he didn't believe in such nonsense as ghosts, and wanted to be shown to the room, as he wanted to get a shave and clean-up before dinner. He said any kind of a room would look good to him after sleeping in the snow for the past week. The Post Manager showed him to the room which was situated at the rear of the large dwelling house, away from the rest of the guests. Mr. R. had just laid out his "glad rags" and was commencing to shave—he had the razor in his hand—when a feeling came over him that he was not alone in the room. Looking into the mirror, he was horrified to see there the reflection of a horrible face peering over his shoulder. He felt his wrist grasped by a claw-like hand. His hand was being forced slowly up and up, towards his throat. Mr. R. tried to call out for help, but he was powerless to utter a sound. The hand was still forcing the razor towards his victim's throat, then it started to draw it across. Mr. R. gave himself up for lost, when he felt the grip on his wrist loosen and a baffled expression came over the horrible face. That ghost was up against modern science. Mr. R. was using a safety razor.
  • 59. SASKATCHEWAN DISTRICT OFFICE NEWS Congratulations would appear to be in order for Mr. and Mrs. Armstrong, of Fort a la Corne Post, and their daughter Norah on the success attained by the latter at the recent St. Alban's College (Prince Albert) term examinations. The following is a quotation from the local paper: "Miss Norah Armstrong, the gold medalist of the year at St. Alban's college, Prince Albert, holds an enviable record in the college. Miss Armstrong has been a student at St. Alban's for the past four years, taking her grade 8 diploma in 1917. She was successful in passing her junior matriculation examination in June, and now holds the St. Alban's scholarship to the University of Saskatchewan. In addition to her marked progress in her studies, Miss Armstrong has found time to distinguish herself along athletic lines, having won the tennis cup in singles, and also with Miss Phyllis Clarke in the doubles."
  • 60. "SKIPPERING A SCOW" ON THE ATHABASCA (Continued from last number) By N. A. Howland When the men in the scow realized their position they did not shout frenziedly for help. To them the most important business of the moment was to get a smoke. They Smoked While Facing Death The frenzied people were all on shore. Under the calming influence of tobacco, the wrecked crew surveyed the damage. The boat was intact though leaking a little. It was impossible for them to extricate themselves. Even if any of them could swim, an attempt to make the shore would have proved fatal. They relied on us. Their hope was founded on a rock as surely as their craft. Getting Ready for the Rescue It was not long ere some of the sixty odd men, at Mr. Cornwall's direction, on the island had run to the warehouse to get rope. Fortunately being on the scene, he took matters in hand, and as soon as the necessary tackle had been brought, essayed to rescue the endangered crew. The only way that this could be done was to get a line aboard the scow and pull her off. The distance from shore was too great to permit of a rope being thrown, but there was a rock standing well out of the water about half way between, from which it might be possible to hurl a stick; so Cornwall, taking a club in his hand to which was attached a long cord held by the men on shore, started to work his way out to the vantage point through the rock-studded stream, struggling from boulder to boulder, the swirling water gripping and tearing at his legs in an effort to sweep him away. Fighting the Torrent
  • 61. To the tense crowd of men watching it seemed impossible that he could attain his object, but in spite of the great physical strain slowly and surely the figure—now waist deep in the current, now pulling himself up on to a rock, clinging always to the meagre support with a tenacity that the raging torrent could not break—reached its goal. Getting A Line Aboard the Wreck A sense of relief came to those who watched, but not for long. He rested for a moment to recover his breath; then coolly gathering the small rope into a coil he made the first throw. A gasp went up from the crowd on shore. The distance was too great; the stick hit the water fully twenty feet short. Again and again the attempt failed. Sometimes the missile fell so close that the rope could almost be reached but they had no boat-hook aboard. The thrower could not stand up with good footing to do his work, but from a precarious position threw with arms alone. He rested, tired by his exertions. Suddenly he gathered all his strength and at imminent hazard of hurling himself into the river sent the stick with unerring aim over its mark. We Pulled the Scow Off the Rock A mighty cheer went up from all the watchers. It was but a moment's work to haul in the cable and make it fast to the end of the scow; every available man on shore found a place on the line, and pulled with might and main to the cry of "Yo heave ho!" that she creaked in every seam and her square end was drawn bow-shaped under the strain on that fragile rope. Pull as we might, our efforts to dislodge her were unavailing. Something had to give, however. It was the line which parted with a snap, hurling us to the ground. A groan went up from those in danger, for in a moment they fell from the highest hope to the lowest depth of despair. They were in worse plight than before, but steadfastly the business of renewing communication with the scow proceeded without delay. Cornwall's efforts were again crowned with success. Little by little our task was accomplished and we were gratified to see the men who were in the water scramble aboard in great haste, as with a rousing cheer we let go the cable. A Tenderfoot Spectator When we had first arrived at the head of the rapids the previous day, a little man with a large outfit was found encamped on the river bank unable to proceed any further, waiting for something or somebody to turn up. Ten days had passed before help arrived. He had been brought hither by a gasoline engine and canoe, his only companions so far as is known being two spaniels. This gentleman styled himself a prospector ostensibly bound for Fond-du-Lac to investigate the silver strike there; but his proceedings and appearance belied the assertion, for if there were a man who should not have left the shelter of the paternal wings, it was he. The impression gained was that he was one of those helpless useless atoms of humanity that are misfits anywhere, but in the North, where one must be self-reliant, doubly out of place. He having arranged with Mr. Cornwall for a "lift" from there to Fort McMurray, lay all day on his bedding in the sand surrounded by his goods and chattels, playing with his dogs, bestirring himself only to take a photograph occasionally or get a bite to eat. Fondled His Spaniels and Looked On
  • 62. He was apparently oblivious to the tragedy being enacted within a hundred yards of him. This man called down upon himself the contempt and scorn of all men present by remaining inert, lazily fondling his spaniels whilst men's lives trembled in the balance. His hand upon the rope would not perhaps have helped much, but we should at least have known that he was a man. The sequel to his apathy was that next day he was deposited on the main land below the rapids and where it was intimated to him that his company was no longer desirable. An All Night Mosquito Raid Whether fired by a spirit of recklessness by the events of the day, or whether the writer was too tired to return to his camp on the mainland with the men is of little consequence, but be it known that his mosquito-bar was there. Needless to say, the mosquitoes were victorious. We needed no alarm clock that morning because the enemy forced me out of bed during the night to upbraid myself for a fool. Not a wink of sleep for me as a result; however, we got an early breakfast out of it. The Tug "Crester" Wrecked My Russians were making good progress removing the rails, the freight having been all portaged, and the scows run through the previous day were being drawn up to the Island and reloaded. About 10 o'clock Captain Barber started to run the tug "Crester" through the rapids without steam, steering with auxiliary in case of accident. Disaster dogged the footsteps of the railroad party apparently. Nothing had gone well so far. The climax had arrived. Those who were watching the river gave a shout. All eyes went to the rapid immediately; there was the "Crester" shooting down through the roughest of the water well over on the land side, out of control. We learned later that her rudder had been smashed. We saw her take a few bad bumps from a distance of two hundred yards; then with a final heave she seemed to be lifted bodily and dashed on the rocks close inshore where she lay a wreck with her bottom stove in, broadside to the current with the waves breaking over her.
  • 63. The "Crester" Dismantled There were no casualties. With the aid of spars, the crew were easily able to make the land. It was the middle of the afternoon before it was possible for me to go over and see the tug. In the space of six hours the captain, engineer and boatmen had her completely dismantled and all her "innards" ashore, whilst preparations were being made to pull her off and float her down the rest of the way into the Big Eddy, where she could be patched up. (To be continued)
  • 64. Moose Island Afire Clergyman's Bonfire Grows Into Conflagration, Threatening H.B.C. Post and Natives' Homes BY GEO. FINDLAY, Moose Factory A Journal extract, dated August 25th, 1920, states briefly that: "The Rev. Mr. Haythornthwaite while burning old tree stumps at the back of the Mission allowed the fire to run on, thereby setting alight the adjoining bush." That day, a Wednesday, was excessively hot, and, as the whole summer had been very warm, all the bush and undergrowth must have been perfectly dry. At 2 o'clock in the afternoon the cry of "Fire" went up, and from the southwest end of the island a big column of smoke began to darken the air, blowing in the direction of the Post. For some minutes the natives stood gazing and then the realization that the Island was afire broke upon them. Something akin to panic set in. Canoes were loaded. Food, blankets and tents were thrown haphazardly into them, and they were swiftly paddled to the opposite bank of the river by the fear-stricken natives. Imagine the scene: The river dotted with canoes, with their multicoloured loads; the roar of the ever-increasing fire, as it was fanned by a slight breeze, and the strange stillness that pervaded the Post, which can be sensed only in a deserted place. The servants returned as soon as their families were safely "entrenched" on the other side of the river, and each with his axe hurried to the scene of the outbreak. In company with Mr. Gaudet, our Post Manager, I went to see the progress made by the fire. Often we were compelled to change our route through the bush on account of the terrific heat and the choking, blinding smoke. In many places great patches of undergrowth were blazing quite a distance from the body of the fire, sparks having been blown ahead by the wind. The roar of the fire was deafening as it caught fresh trees, shooting great lurid tongues of flame up their entire thirty feet. Darker and darker grew the air; the heat became fiercer; the fire advanced as if to satisfy its terrible hunger by enveloping the entire Island in its scorching clutch; and as we walked back to the deserted Post thoughts of having to abandon it ran through our minds. However the wind dropped, and the little band of fire fighters worked hard to accomplish their task. Had the wind risen, the whole island would have been devastated. All that night, and the succeeding five days and nights, gangs of natives (who had by this time got over their fright) and servants watched the fire until it was successfully stamped out.
  • 65. Assembly of Indians who received H.B.C. Long Service Medals at Fort Alexander Robust sons of Post manager W. A. Murray, at Fort Alexander, Manitoba
  • 67. WINNIPEG RESOLVED Jan. 1, 1921 that New Year's resolutions are not going out of fashion, as witnessed by the following answers to the query, "What is One of your New Year's Resolutions." J. H. Pearen—To remain young that I may laugh with my children. To be considerate at all times of the aged and infirm or those in need of encouragement. W. Ogden—To think more, talk less and to go through each day fully realizing that the opportunities which come to me lie in the present and not in the future. Thos. F. Reith, Card-writer—That I try to emulate the well-known Beaver and turn out heaps of Bright Effective Artistic Vigorous Enterprising and Readable show cards, tickets and signs during 1921, in which case I expect to "BE-A-VER-"Y busy Card-writer. Geo. W. Ashbrook—It is my opinion that a New Year's resolution, if sincere, should be confined to the individual's eye alone and not open to the gaze of the public. S. Kaufman—One of my resolutions for 1921 is to endeavor to reduce my weight twenty pounds by applying myself assiduously to the royal sport of curling during the winter season and by strenuously playing tennis during leisure hours in the summer time. Miss D. Bens—To be true to my word, my work and my friends. To make all I can, to save all I can and give all I can. J. W. Frankish—We are aiming at 100% efficiency in selling our merchandise. It should be sold on the same basis as we buy it. More attention by sales staff in introducing all the new merchandise as it enters the department. This is our intention in departments 3 and 5 for 1921. Chas. Healey—Do it now! This is my New Year's resolution. It is so easy to put things off when just a little "pep," a little extra energy is needed. So much can be gained and greater satisfaction can be given to all. Do it now! A. C. Dunbar—I will increase my efficiency—(power to produce)—by studying, plus analyzing, plus determination, plus application, equals increased efficiency.
  • 68. J. Whalley—That every business act of mine will be executed with the full belief that it is for the best interest of the firm. Saml. Drennan—To continue placing more confidence in the washboard than in the Ouija board. I. N. Cognito—Not to engage any more handsome looking salesgirls, as those I now have are all engaged—and may get married. W. R. Ogston—One of my resolutions for the New Year will be to govern my actions, thought and speech towards my fellowmen by the well-known principle of "The Golden Rule" and to do my work in such a way that at the close of each day I may feel that I have accomplished something. Winnipeg Moustache Club Semi-Annual Report Just prior to the closing of the outfit ending January 31st, 1920, a careful inventory discloses the following state of affairs. The showing is not entirely satisfactory, but it is felt that some progress is being made. Moustaches on Hand—None. Moustaches on Upper Lip—Twenty divided among the following "heads of stocks": Messrs. Frankish, Goody, Grant, Moore (tailoring), Lade, Fuller, Hughes, Lackie, Weeden, Blowers, Leveque, Dickens, Harrison, Hardiman, Keeley, Chambers, Duckneau, Breitner, Clark, Pugsley (?). New Member—Mr. T. Nichols. (Greetings, brother). Under Suspicion—Mr. C. M. Thomas, Mr. C. Robinson, Mr. Robt. Cunningham. The Club's National Anthem—"The Bonnie Bloomin' Heather." Legend for Club's New Escutcheon—"The Weight of a Hair Will Turn the Scales."— Shakespeare. Remarks—All members and supporters are urged to consult Mr. Saalfeld re irregularities of growth observed from time to time. Renovation for spring should be undertaken early. Special rates to members for loan of Hoover electric sweepers. Use of garden rakes or weeders will result in suspension from Club privileges. Special attention is called to the alarming recurrence of the grasshopper plague prophesied for June and July.
  • 69. DO YOU REMEMBER this remarkable aggregation? This is the formidable H.B.C. Football Team, Season 1911-12. From left to right—Madill, Jones, Medland, Isaacs, Everitt, Paul, Brodie, Dyde, Foulks, Sheldon, Campbell, Mr. A. H. Doc, Law, Smith, Allan. Managers' Social Dramatic Affair As merry a company as ever graced a festal board met at the store buyers', managers' and assistants' social in the lunchroom, Thursday evening, January sixth. The highly edible and diversified "wittles" were disposed of with a display of "wim" and "wigor" which did justice to all traditions. Entire arrangements for the occasion were undertaken by the ladies, and the zest with which the entertainment proceeded brought down the applause of the whole assembly. Speech, anecdote, jest, song and a three-act drama, starring the celebrated tragedian, Samuel Drennan, were features of an altogether enjoyable and profitable evening. Are We 100 Per Cent Efficient? By R. J. HUGHES I wonder how many of us could answer the question at the head of this article truthfully without a considerable amount of self-study, and if we did stop and analyze ourselves would we find that we could say, "Yes, I am 100 per cent. efficient." Now, let us consider for a minute what "efficient" really means. Turning to your dictionary, you will find the definition, "capable of producing the desired results." Are we really prepared to say "yes, I am capable of producing the desired results." If you can't, you are not 100 per cent. efficient and must find the reason why. It does not matter what position you hold or what the nature of your work is, if you are efficient, advancement is bound to be waiting. In a recent issue of The Beaver was a copy of what was called "A man-rating chart" and a statement that stores' staff promotions are governed by efficiency. Study this chart and
  • 70. see how many points you can honestly claim to have mastered. Whatever you do, don't go round like some people saying, "I am 100 per cent. efficient." If you really are, the management will soon notice it and promotion will come your way. Next month I will tell you what an important part memory takes in efficiency. Y-O-U! What's the Matter With You, Anyway? By ELMER PUGSLEY There are two ways, 'tis said, by which to get into "society"—either by flattering or shocking it. But though the writer had the honeyed tongue of the anteater, this is no time to coddle and soothe you with some linseed-poultice sort of caressing lullaby. It's New Year's and I am deliberately setting out to fire up your "dander." Of course, you may be able to prove an alibi, but, otherwise, if these few plodding lines succeed in making you really boiling, red-hot "mad"—(not just angry, you understand)—that will be the best proof that you're still conscious—and there's hope for you. We shudder when we read of "so and so" being picked up unconscious, but I could pick up numbers of people in that pitiable predicament any day—people who somehow got into the business world, strange to say. You stand at the outset of a New Year. Scientists think there have been living beings on this old planet for 500,000 of those time-measures we call years—but there is only one you can be sure of—that's this year. It's a wonder you didn't think of that without being told! Glance back over the old year's glimmering trail now fading into whatever such things fade into. It is strewed with regrets and wasted opportunities that slipped through your careless fingers! Aren't you ashamed? What's the matter with you anyway? Don't you care much? Aren't you interested in the big proposition called "life", more than just enough to watch the procession of progressive mortals passing? You'll never keep up with them if you don't pad right along! Wouldn't you like to strike out for a real goal, eh? You have the stuff in you if you'd just shake yourself a little to rouse your rusting gifts. Don't turn over the key to the bailiff just because you weren't born under a favorable sign in the zodiac. Even if your teacup doesn't read right—pshaw! you wouldn't let a thing like that spoil your future! Never mind if the bumps on your head are in the wrong place; jump into the scuffle and you'll receive any other bumps you need before you're through. A chap is said to have advertised his brains for sale the other day—"good as new—never been used." He never served in The Hudson's Bay, that fellow. No, sir! The very air is surcharged with pleas to you to launch out and distinguish yourself. Self advancement is the theme of the age. No one can do as much for you as you can do for yourself. You're a regular "powerhouse" of possibilities if you have enough gumption to utilize them. You remember you turned down a smashing good chance to get ahead, when, for the sake of a few paltry frivolities, you sacrificed that special study course which you could have mastered in 1920. You know better than that. You saunter along
  • 71. through life as if you had a thousand years to put in here. Train the microscope on your freckled career and set about to remedy things. Come now, get hold of yourself! It's all beginning over again—New Year—new page—new everything! Tackle something that's so much bigger than you that it scares you! That's the way to grow accustomed to accomplishing big things. This is your year! How do you know that you're going to have another as good? Make this your motto—pin it to your New Year's resolutions—"This is My Year!"—and in sooth it will be your year! Miss McCheyne's name was inadvertently omitted from the formerly published list of names of those completing ten years' service. Since the change in markets Miss Winslow, our postmistress-in-general, is worried for fear someone is going to tear in one of these days and ask what the new replacement price is on two cent postage stamps. Someone turns in an unsigned report about the prevalence of "sparklers" getting hard on the eyes around the bureau of adjustment. First Snowshoe Tramp By Land Staff Eighteen members of the Land Department staff snowshoed out to the home of Mr. B. Everitt, our genial associate editor, at East Kildonan, Saturday evening, December 18th. The party gathered at Redwood bridge and tramped north by way of Red River. About half way it was found necessary to call a halt owing to the guide being missing. His rejuvenated appearance upon eventually overtaking the main party led to some doubt as to the generally accepted meaning of "air holes," which were reported to be the cause of the delay. While there was not sufficient snow to make real good tramping, what was lacking in this respect was more than compensated for by the enjoyable time provided by the host and hostess at the conclusion of the hike. Here games and dancing were indulged in until midnight, when the party was brought to an end with the singing of "Auld Lang Syne."— F.H.N. An Error Rectified As some error in the names of the long service medalists had been made at the opening of the Anniversary Celebration, our general manager's office was the scene the other day of a pleasant little ceremony when Mr. Chas. E. Robinson was made the recipient of his long service medal. It was presented by Sir Augustus Nanton, chairman of the Canadian Advisory Committee, Mr. FitzGerald and Mr. Sparling being also present. "Charlie" has been with the Store since June 6, 1904, and is one of the bulwarks. Mr. James Thomson, former Commissioner of lands and furs, was warmly welcomed home at Winnipeg, December 23rd, after an absence of several months in the Orkney's and Scotland.
  • 72. EDMONTON LAND OFFICE Our photograph shows Mr. J. R. McIntosh, H.B.C. Land Agent in charge of the Edmonton Land Office, with his secretary and Mr. Henderson (standing). Mr. McIntosh and staff who are actively associated with the Company's housing scheme, operate from these modern offices in the McLeod Building. Retail Store Notes Recent Changes Among Store's Department Heads Changes never seem to come singly, for since the first appearance of The Beaver no less than five important executive appointments have been made in the store; and another is scheduled for the very near future. Mr. Chasey, the new buyer for the men's clothing departments, and Miss M. Doherty, the new buyer for the hosiery and gloves, are now firmly established on their feet and are making noteworthy progress. We now welcome to our ranks three more recent arrivals:
  • 73. Mr. Pallett is another Easterner who has heard the call of the West. Mr. Pallett succeeds Mr. Jenkins as buyer of the trimmings and ribbons. He was previously with the T. Eaton Company for several years. Mr. Pallett is very favorably impressed with the City of Edmonton and predicts a great future for the store. Mr. Secord is the new buyer of the ladies' ready-to-wear, and successor to Mr. Woodman. Mr. Secord was previously with the Robert Simpson Co., of Toronto, nine years buyer of the ladies' ready-to-wear and fur department. Since coming to the store, Mr. Secord has won the esteem of the entire staff and we predict a rosy future for the department under his supervision. Mr. J. McLeod has succeeded Mr. McKee as buyer of the cigar and candy departments. Mr. McLeod was recently floor manager on the second floor and was previously manager of the grocery department, Hudson's Bay Company, Retail, Vernon, B.C. Hail to Our New Assistant "Chief" This new appointment was effective on December 13th, 1920. Besides holding the position of assistant manager, Mr. McKenzie will also act in the capacity of merchandise manager, thereby relieving Mr. F. F. Harker of a big burden. Mr. Harker has for the past twelve months acted in the dual capacity of manager of the store as well as merchandise manager. Mr. G. M. McKenzie was born in Edinburgh, Scotland, serving his apprenticeship in the dry goods and men's wear business. In 1901 he came to Canada and joined the firm of Jaeger & Company, subsequently holding the position of stores manager and supervisor of the factory in Montreal. In 1916 Mr. McKenzie heard the call of his country and proceeded to the front, serving with His Majesty's forces in France until March, 1919. Upon returning to Canada he accepted a position with the R. J. Tooke Company as general manager of the retail stores in Montreal. His recent appointment as assistant manager of the Edmonton store will fill a long felt want.
  • 74. Mr. P. A. Stone, president of the Amusement and Athletic Association, which has grown to embrace a dozen varied athletic and social activities since its inauguration in September, 1919. Mrs. Lewis recently rejoined the staff after an absence of two years. She is in charge of the lace and neckwear department. We are glad to welcome her back. Miss Law is also an old member of the staff who has recently come back to the store. During her absence she was with the Company's store at Calgary. She is resuming her duties here in the ribbon department. Miss McAdam, who has been in the Company's service for the past seven years, has left us for the coast. Miss McAdam was a very popular member of the staff and we regret
  • 75. exceedingly to lose her. Mr. Howey, of the men's furnishings department, is an expert hockey player. We have no doubt he will be a valuable acquisition to the store's team. Mr. C. Stapells, house furnishings buyer, and Mr. Hewes are very busy these days supervising the draperies and furnishings for the palatial new Empire theatre. We have heard that a certain young lady on the third floor has lost her heart and is going to sign a life contract in the very near future. The A. and A. A. Concert Reveals Real Artists Another of those very enjoyable concerts which are staged periodically through the winter months by the Amusement and Athletic Association, was held in the "Hudsonia" dining room on Thursday evening, December 2nd, at which about 150 members and their friends were present. The association was again fortunate in hearing Mr. R. L. Bateman, who rendered "She Is Far from the Land" and, in response to a hearty encore, "For You Alone" was all that could be desired. Miss Kate Hamilton sang "Bird Songs" in which her beautiful voice was heard to very great advantage. Mrs. Roy Carbert sang Tosti's "Good Bye," and as an encore, "Angus MacDonald." Mr. Bert Crockett sang "There's Life in the Old Dog Yet," which was very much appreciated, he being vociferously encored. All the other artists are members of the staff and their songs were all rendered in admirable style. One exceptionally pleasing number was the duet, "Tenor and Baritone," Mr. T. A. Crockett's tenor and Mr. Digney's baritone voices blending in perfect harmony. Miss Edna Southen and Miss K. Riddle were two excellent sopranos, whilst Miss W. E. Crowther's sweet contralto voice has never been heard to greater advantage. Mr. T. A. Crockett and Mr. George Saunders have fine tenor voices, whilst Mr. G. Robert's deep bass was used with effect in "Out on the Deep." Mr. C. Digney was splendid in "Captain Mack" and later his rendering of "My Old Shako" was perfect. Miss Moore acted as accompanist throughout and in addition gave a duet in company, with her sister. One cannot speak too highly of Miss Moore's assistance, as she is always ready and willing to help in any way that will add to the enjoyment of the staff, whether it be as accompanist or soloist. Mr. P. A. Stone, president of the Amusement and Athletic Association, acted as chairman. Community Singing is Getting Results
  • 76. Community singing for the staff, which was inaugurated at the Edmonton store, November 1st, 1920, is reported to be an unqualified success. The staff arrive at 8.45 a.m. and sing usually two songs before 8.55 a.m. bell sounds, when the covers are removed preparatory to the day's business. The initiative was taken by the Amusement and Athletic Association. The fact that it is still retaining the original interest proves that the all-important co-operation has been obtained; hence the success. Whilst it is impossible yet to gauge the full extent of the benefits derived from community singing, it may be said that the early morning "grouch" is dissipated, and that alone makes it worth while, as it leaves the staff in a happier frame of mind. This cannot but conduce to the betterment of the service afforded to customers. From community singing to a trained choir is but a step, since even the untrained singer gradually falls into and holds the time and rhythm of the piece being sung, so that from an untrained band of voices a perfectly functioning choir is created. This is the aim of the Edmonton Amusement and Athletic Association, and with a continuance of the staff's co-operation that end will be attained. The Ad. Man's Destiny Mr. Jack Prest was going home one night in the street car. It was late, and the man sitting next to him began to talk. "What business are you in?" he asked. "The advertising business," replied Jack. "Is that so? Well, well, I used to be in the advertising business myself. I gave it up though and went into the rag-and-old-bottle business. I was a sandwich man for the Empire Theatre for six months." "Say," and he leaned over confidentially, "Ain't it hard when the wind blows?"
  • 77. CALGARY The Rank and File By F. R. REEVE The newspapers recently had much to say concerning the remarkable honors paid in England and France to the bodies of two unknown soldiers who fell on the battlefields. It was a nation's whole-hearted recognition of the fact that Victory was after all due to the efforts and self-sacrifice of the rank and file. In the scheme of life each one of us has a definite sphere to fill. Lest those who now constitute the rank and file in the service of the Company should be inclined to regard their positions with something of dissatisfaction, as being of no importance, I would have them take a lesson from the honors paid to these two unknown soldiers. Upon those who constitute the front rank, those who come in contact with the public, the whole success of this great Company depends. Behind you it is true, stretches a long line that reaches back from the junior buyer, through to the Governor himself, but the work accomplished by this wonderful organization does not reach its greatest success except through your co-operation. The transaction between a customer and salesperson is not just so much money changing hands for a certain article. It represents the crowning success of a long series of operations, that, through your hands as the H.B.C. representative, reaches the goal for which it was intended, an appreciative buying public. Upon the conduct of the rank and file—upon the impressions that are derived from your personality—is this Company judged. The courtesy, helpfulness and efficiency that are displayed by you are the greatest assets this Company has. To know and to realize that no matter what your position in the service of the Company may be, that the Company is absolutely depending on your efforts will be to create in you a greater desire for helpfulness and efficiency which cannot fail to mean greater success for yourself and Company too.
  • 78. VANCOUVER Everybody Boost for Our 1921 Hockey Team It has been asked of the editor why there were not more attending the hockey games last winter, and why the H.B.C. employees were very backward in supporting their own team, being especially conspicuous by their absence. We've a dandy team this year, folks, and the boys sure would like some "rooters." Come along and bring your friends and the horn off the old Ford. Help the team make a name for themselves in the Commercial League. The following are the names of our players: W. E. Almas (Capt.) E. Herbert P. Timmins Chub Anderson R. M. Mair J. Gilroy J.C. Hamm J. McDonald J. D. Barber C. Boe We were very grieved to hear on December 10th of the death of Mr. Patterson, husband of Mrs. W. Patterson, cashier in our children's shoe department. We are also bereaved of one of our old employees, Mr. James Hallisy, who passed away at his home on December 10th. The deceased was on our night staff, and had been in the Company's employ since 1918. The army and Navy League Hall again witnessed a popular H.B.C. dance. Approximately 350 attended and tripped the light fantastic to the strains of Garden's orchestra. Mr. Skelly, chairman, and his competent committee had charge of the affair, which was carried off without a hitch to a very successful ending. Mr. Lockyer Elected President of Vancouver Exhibition Association
  • 79. Holding their first meeting since taking office, the directors of the Vancouver Exhibition Association on Dec. 16th elected Mr. H. T. Lockyer, manager of the Hudson's Bay Company, Vancouver retail store, as president for the ensuing year.—Vancouver Province. Mr. W. W. Frazer, the popular buyer for china and glass, left for Europe in the interests of his section, early this month. Many laudatory remarks were overheard by Eastern and American tourists anent his last collection of lovely china. Mr. Frazer apparently knows where to get them. "Where do they get all these pretty patterns—there's not an ugly one among them"—exclaimed a lady from Ottawa recently, and went on to say she had never seen a better display in New York, Montreal or Toronto. But that's Mr. Frazer's secret. We wish him bon voyage and the best of luck this time. Miss A. K. Smith, too, buyer of notions, neckwear, laces, trimmings, hankies and fancy jewellery, has been chosen for a trip abroad after the airy fairy "nothings"—"the stuff that dreams are made of"—that are so dear to feminine hearts. Her return from Europe ladened with spoils will be looked forward to with interest by her constituency in Vancouver. You may be sure Miss Smith will not overlook any of the cute or smart little knick-knacks that are being shown in the marts over there, and we shall all have an opportunity to be more than ever up-to-date on her return. Vancouver is to be congratulated on having two buyers in whom the Company has so much faith and confidence as to entrust with this important foreign buying. The Tell-Tale Inventory A Vancouver bailiff went out to levy on the contents of a house. The inventory began in the attic and ended in the cellar. When the dining-room was reached the tally of furniture ran thus: One dining room table, oak. One set of chairs (6), oak. One sideboard, oak. Two bottles of whiskey, (full)! Then the word "full" was stricken over and replaced by "empty" and the inventory went on in a hand that struggled and lurched across the page, until it closed with: "One revolving door mat." Mr. Greer Gets a Regular Shower of Good Things By E. Bell Of the recent year end festivities enjoyed by Hudson's Bay employees perhaps none had more of the vivres and relish of the days of real sport than the banquet tendered Mr.
  • 80. Greer by his staff in the display department. This event took place in the Barron Hotel to begin with and ended at a box party to the opera to witness the "Dance Shop." The menu of the dinner, which was enjoyed both wisely and well, gives some of the unlucky individuals who were not invited an appetizer even to read: Greer Soup Goose a la Greer Oyster Cocktail, Y.M.C.A. Celery a la Celestial Citizen Brussels Sprouts a la Lulu Island Fried Sweet Potatoes, Brunette Hot Toasted Rolls, Blonde Combination Salad a la Display French Pastry Translated Cake, Devilled Creme de Chaufroid Cafe d'Hots D'el (N.B.—S.O.S. Calgary. M. Laparique, please note. Can you beat it?) Having done full justice to these delectable viands the innocent occasion of so much mirth was next trotted to the opera, where his friends had taken the precaution to present him with a lorgnette or opera glass, we forget which. (Anyway it was not a monocle.) Notwithstanding, to the everlasting credit of the display department, they all turned up next morning on time and in the best of spirits. Old-Time Employees Visit the Store Among the guests of the Store last month were Mr. and Mrs. Alexander J. Baird, both old- time employees of the Company, who devoted a number of years of faithful service in the old store and two or three years in the new store. Mr. Baird was secretary to the general manager, Mr. Lockyer. In 1917, he went to Honolulu for a new field to conquer. He was there but a little while before he sent for his fiancee, Miss Beck, then the general manager's stenographer. As soon as she arrived in Honolulu they were married. Being accustomed to speculating and used to seeing money made out of land, Mr. Baird (in face of much opposition) bought a piece of land and built three cottages thereon—an investment which proved a good one and a money maker.
  • 81. KAMLOOPS H.B.C. Kamloops Store Dates Back to 1812 Location Has Changed Several Times to Keep Pace With Growth of City By A.E. DODMAN The Company's store at Kamloops dates back to the year 1812 and it is therefore one of the oldest establishments at present existing in the stores department. The original location was some distance from the present store site, as, like all Western towns, the business centre has changed several times, and the Company found it necessary to change from time to time in order to keep pace with the natural growth of the city. The present premises were purchased and remodelled by the Company in 1911, and have a frontage of 75 feet on Victoria Street, extending 125 feet on Second Avenue with two entrances on Victoria and one on Second Avenue. The building consists of two stories and basement. In addition the Company also operates a wholesale and retail tobacco and candy business on rented premises situated at the corner of Victoria Street and Third Avenue. The business at Kamloops comprises eight departments—general dry goods, ladies' wear, men's furnishings, boots and shoes, crockery and hardware, house furnishing, groceries and tobaccos. Miss Brooke, of the grocery staff, resigned her position with the Company and was married on January 1st, 1921. She was presented with a travelling bag by the staff. We wish her all kinds of joy and happiness in her new venture. She was a real "good fellow" and will be greatly missed by us. Miss Muir has accepted the position made vacant by Miss Brooke of the Grocery Department. We wish Miss Muir every success. Miss Cozens says she was never "locked out" in her life, but she experienced the feeling of being "locked in." She says "never again." The Staff presented Mr. A.E. Dodman, our store manager, and Mrs. Dodman with a Christmas gift of a very handsome tea set with best wishes. A rumour is heard to the effect that Mr. McDonald, the accountant, has become an expert dancer, and has accepted an invitation to teach three ladies the fine points in dancing. Nice for Mac, but kind of tough on the ladies.
  • 82. After a very busy and most successful Christmas trade the staff have settled down for the most successful January sale we have ever had.
  • 83. VERNON Entire Staff a Santa Claus to Mr. Pout, Xmas On Christmas Eve, at the close of the biggest day in the history of the Vernon Store, the staff gathered for a few minutes to extend good wishes and exchange tokens of friendship. At the conclusion, Mr. Pout was captured when trying to tip-toe off, set securely within the smiling circle, and compelled to listen to the following effusion which Tom Bone, the store poet, says he did not compose. It is now being blamed on Jack Ricketts, and so far Jack hasn't denied it.
  • 84. Our dear respected Mister Pout We guess you guess what we're about; If not, you won't be long in doubt, But get the sense, So we shall quickly put to rout Your dread suspense. It's Christmas time, as you well know, And we have gathered here to show That years may come and years may go, With rush and zest, But our good feelings far outgrow This timely test? It gives us joy to give to you This coffee service, bright and new, And wish that all things good and true That hope conjures, May travel all the next year through With you and yours. Mr. Pout was too full for words (honi soit qui mal y pense), but he managed to express his hearty thanks for the splendid support and co-operation he had received from the entire staff during the Christmas rush, also for the kind thought which prompted the giving of such a beautiful gift. The coffee pot was one of those long narrow "prohibition" coffee pots that you are unable to tell what is inside of until you taste the contents. Tom Harrison struck up "He's a Jolly Good Fellow." "Arry" thought it was "Auld Lang Syne" and started off on his own, while James Henderson, in an endeavour to put them both right, commenced "Will You No Come Back Again." When the company broke up, those three were still at it, and nobody could tell which was winning.—R.W. Miss Cridland, treasurer of our Sisters' Sewing Circle, has been absent from the meeting several week. We were surprised to see her at the last meeting. She says her absence has been due to the fact that she had to attend "prayer meetings." We have since learned that a certain young man's "tin Lizzie" is being overhauled. May it take all winter —so Gladys will be at every meeting.
  • 85. Miss Phillys Ripley, the girl with the sparkling eyes, assisted for several weeks in the hardware department but is back once again at her old stand tying bows for the kiddies. Her eyes still sparkle and there are many beaus waiting for her to cast her spell on one of them so that two may be tied into one bow. "Wonderful how popular some men are," said Watson, when he heard what happened Christmas Eve. The girls in the dry goods department placed mistletoe on the light over Mr. Andrews' desk—and not one missed him, even Mabel had hers. Nuff sed. Mr. Tom Bone, assistant manager of the grocery department, the staff poet, has changed his vocation and now spends his evenings making musical instruments. We wonder if it will be jazz or operatic music. We are glad to learn that Mrs. Griffin, wife of C. Griffin of the men's department, is home once again after being confined to the Hospital several weeks with typhoid fever. We all wish her a speedy recovery. Vernon, Gem of the Okanagan —and the H.B.C. Store, One of Its Institutions Thirty years ago, there were only two stores in Vernon, The Hudson's Bay Company and W.F. Cameron, both firms carrying a general line of merchandise. The only other stores in the Okanagan Valley, at this period, were one at Enderby, Landsdowne, Okanagan Mission and Penticton, so that these stores supplied the necessities of life practically to the whole of the Okanagan Valley, reaching from Sicamous to fifty miles beyond Penticton and from Grand Prairie to the White Valley district. The towns of Armstrong and Kelowna, at this period, were not in existence. Travelling in the early days was by stage and boat in Summer, the boat running from Sicamous to Enderby, thence by stage to Vernon, and the only method of travelling in Winter was by stage or pack horse. Mail, also, was received by these means of transportation. The great bulk of trading, at that time, was done with Victoria, which was a greater commercial centre than Vancouver. All merchandise from the Coast was carried by freight trains to Sicamous, transferred there to a small steamer as far as Enderby and thence by wagon to Vernon. Business conditions and the manner of trading in the early days were entirely different to the present day method. There were no banks in the Valley, all banking being done through Vancouver, cheques often passing around as currency and would have as many as a dozen endorsations before reaching the bank. Yearly credit was the system of trading. Farmers, ranchers, trappers and Indians paid their accounts once a year after they had received money for their crops and catch of furs; the amusing feature in regard to the credit in these days being that the average customer would ask of his account, simply looking at the total and settling up without checking up. Considerable business was done in the bulk, tea sold by the chest, flour and sugar by the ton, and other commodities in similar large quantities.
  • 86. Welcome to our website – the perfect destination for book lovers and knowledge seekers. We believe that every book holds a new world, offering opportunities for learning, discovery, and personal growth. That’s why we are dedicated to bringing you a diverse collection of books, ranging from classic literature and specialized publications to self-development guides and children's books. More than just a book-buying platform, we strive to be a bridge connecting you with timeless cultural and intellectual values. With an elegant, user-friendly interface and a smart search system, you can quickly find the books that best suit your interests. Additionally, our special promotions and home delivery services help you save time and fully enjoy the joy of reading. Join us on a journey of knowledge exploration, passion nurturing, and personal growth every day! ebookbell.com