JSP and struts programming

Enterprise Java Jan-June 2015
Prepared by: Mr. Hitesh Kumar Sharma & Mr. Ravi Tomar Page 1
Prepared for : B.Tech CS VI Sem (MFT+O&G+OSS+CCVT)
LECTURE NOTES
UNIT 4: JSP & STRUTS PROGRAMMING
• Introduction to JSP and problem with Servelts.
• JSP Elements
• JSP Directives: page directive, include directive, taglib directive.
• JSP Declaration,JSP Expression, JSP Scriplets
• Implicit Objects
• Attributes: Application, request, session, page.
• JSP Life Cycle.

1.JSP (JAVA SERVER PAGES)
JSP technology is used to create web application just like Servlet technology. It can be thought
of as an extension to servlet because it provides more functionality than servlet such as
expression language, jstl etc. A JSP page consists of HTML tags and JSP tags. The jsp pages are
easier to maintain than servlet because we can separate designing and development. It
provides some additional features such as Expression Language, Custom Tag etc.
1.1.ADVANTAGE OF JSP OVER SERVLET
There are many advantages of JSP over servlet. They are as follows:
1) Extension to Servlet
JSP technology is the extension to servlet technology. We can use all the features of servlet in
JSP. In addition to, we can use implicit objects, predefined tags, expression language and
Custom tags in JSP, that makes JSP development easy.
2) Easy to maintain
JSP can be easily managed because we can easily separate our business logic with presentation
logic. In servlet technology, we mix our business logic with the presentation logic.
3) Fast Development: No need to recompile and redeploy
If JSP page is modified, we don't need to recompile and redeploy the project. The servlet code
needs to be updated and recompiled if we have to change the look and feel of the application.
4) Less code than Servlet
In JSP, we can use a lot of tags such as action tags, jstl, custom tags etc. that reduces the code.
Moreover, we can use EL, implicit objects etc.
1.2.LIFE CYCLE OF A JSP PAGE
The JSP pages follows these phases:
• Translation of JSP Page
• Compilation of JSP Page
• Classloading (class file is loaded by the classloader)
• Instantiation (Object of the Generated Servlet is created).
• Initialization ( jspInit() method is invoked by the container).

• Reqeust processing ( _jspService() method is invoked by the container).
• Destroy ( jspDestroy() method is invoked by the container).
Note: jspInit(), _jspService() and jspDestroy() are the life cycle methods of JSP.
As depicted in the above diagram, JSP page is translated into servlet by the help of JSP
translator. The JSP translator is a part of webserver that is responsible to translate the JSP page
into servlet. Afterthat Servlet page is compiled by the compiler and gets converted into the
class file. Moreover, all the processes that happens in servlet is performed on JSP later like
initialization, committing response to the browser and destroy.
1.4.CREATING A SIMPLE JSP PAGE
To create the first jsp page, write some html code as given below, and save it by .jsp extension.
We have save this file as index.jsp. Put it in a folder and paste the folder in the web-apps
directory in apache tomcat to run the jsp page.

index.jsp
Let's see the simple example of JSP, here we are using the scriptlet tag to put java code in the
JSP page. We will learn scriptlet tag later.
1. <html>
2. <body>
3. <% out.print(2*5); %>
4. </body>
5. </html>
It will print 10 on the browser.
1.4. THE JSP API
The JSP API consists of two packages:
1. javax.servlet.jsp
2. javax.servlet.jsp.tagext
JAVAX.SERVLET.JSP PACKAGE
The javax.servlet.jsp package has two interfaces and classes.The two interfaces are as follows:
1. JspPage
2. HttpJspPage
The classes are as follows:
• JspWriter
• PageContext
• JspFactory
• JspEngineInfo
• JspException
• JspError
THE JSPPAGE INTERFACE
According to the JSP specification, all the generated servlet classes must implement the JspPage
interface. It extends the Servlet interface. It provides two life cycle methods.

Methods of JspPage interface
1. public void jspInit(): It is invoked only once during the life cycle of the JSP when JSP page
is requested firstly. It is used to perform initialization. It is same as the init() method of
Servlet interface.
2. public void jspDestroy(): It is invoked only once during the life cycle of the JSP before the
JSP page is destroyed. It can be used to perform some clean up operation.
THE HTTPJSPPAGE INTERFACE
The HttpJspPage interface provides the one life cycle method of JSP. It extends the JspPage
interface.
Method of HttpJspPage interface:
1. public void _jspService(): It is invoked each time when request for the JSP page comes to
the container. It is used to process the request. The underscore _ signifies that you
cannot override this method.
We will learn all other classes and interfaces later.

1.5.JSP SCRIPTLET TAG (SCRIPTING ELEMENTS)
In JSP, java code can be written inside the jsp page using the scriptlet tag. Let's see what are the
scripting elements first.
Scripting elements
The scripting elements provides the ability to insert java code inside the jsp. There are three
types of scripting elements:
• scriptlet tag
• expression tag
• declaration tag
1.5.1. JSP SCRIPTLET TAG
A scriptlet tag is used to execute java source code in JSP. Syntax is as follows:
1. <% java source code %>
Simple Example of JSP scriptlet tag
In this example, we are displaying a welcome message.
1. <html>
2. <body>
3. <% out.print("welcome to jsp"); %>
4. </body>
5. </html>
Example of JSP scriptlet tag that prints the user name
In this example, we have created two files index.html and welcome.jsp. The index.html file gets
the username from the user and the welcome.jsp file prints the username with the welcome
message.
index.html
1. <html>
2. <body>
3. <form action="welcome.jsp">
4. <input type="text" name="uname">
5. <input type="submit" value="go"><br/>

6. </form>
7. </body>
8. </html>
welcome.jsp
1. <html>
2. <body>
3. <%
4. String name=request.getParameter("uname");
5. out.print("welcome "+name);
6. %>
7. </form>
8. </body>
9. </html>
1.5.2. JSP EXPRESSION TAG
The code placed within expression tag is written to the output stream of the response. So you
need not write out.print() to write data. It is mainly used to print the values of variable or
method.
Syntax of JSP expression tag
1. <%= statement %>
Example of JSP expression tag
In this example of jsp expression tag, we are simply displaying a welcome message.
1. <html>
2. <body>
3. <%= "welcome to jsp" %>
4. </body>
5.
6. </html>
Note: Do not end your statement with semicolon in case of expression tag.
Example of JSP expression tag that prints current time
To display the current time, we have used the getTime() method of Calendar class. The

getTime() is an instance method of Calendar class, so we have called it after getting the
instance of Calendar class by the getInstance() method.
index.jsp
1. <html>
2. <body>
3. Current Time: <%= java.util.Calendar.getInstance().getTime() %>
4. </body>
5. </html>
Example of JSP expression tag that prints the user name
In this example, we are printing the username using the expression tag. The index.html file
gets the username and sends the request to the welcome.jsp file, which displays the
username.
index.html
1. <html>
2. <body>
3.
4. <form action="welcome.jsp">
5. <input type="text" name="uname"><br/>
6. <input type="submit" value="go">
7. </form>
8. </body>
9. </html>
welcome.jsp
1. <html>
2. <body>
3. <%= "Welcome "+request.getParameter("uname") %>
4. </form>
5. </body>
6. </html>

1.5.3. JSP DECLARATION TAG
The JSP declaration tag is used to declare fields and methods.
The code written inside the jsp declaration tag is placed outside the service() method of auto
generated servlet.
So it doesn't get memory at each request.
Syntax of JSP declaration tag
The syntax of the declaration tag is as follows:
1. <%! field or method declaration %>
Difference between the jsp scriptlet tag and jsp declaration tag ?
Jsp Scriptlet Tag Jsp Declaration Tag
The jsp scriptlet tag can only declare
variables not methods.
The jsp declaration tag can declare variables
as well as methods.
The declaration of scriptlet tag is placed
inside the _jspService() method.
The declaration of jsp declaration tag is
placed outside the _jspService() method.
Example of JSP declaration tag that declares field
In this example of JSP declaration tag, we are declaring the field and printing the value of the
declared field using the jsp expression tag.
index.jsp
1. <html>
2. <body>
3.
4. <%! int data=50; %>
5. <%= "Value of the variable is:"+data %>
6.

7. </body>
8. </html>
Example of JSP declaration tag that declares method
In this example of JSP declaration tag, we are defining the method which returns the cube of
given number and calling this method from the jsp expression tag. But we can also use jsp
scriptlet tag to call the declared method.
index.jsp
1. <html>
2. <body>
3.
4. <%!
5. int cube(int n){
6. return n*n*n*;
7. }
8. %>
9.
10. <%= "Cube of 3 is:"+cube(3) %>
11.
12. </body>
13. </html>

1.6. JSP IMPLICIT OBJECTS
There are 9 jsp implicit objects. These objects arecreated by the web container that are
available to all the jsp pages.
The available implicit objects are out, request, config, session, application etc.
A list of the 9 implicit objects is given below:
Object Type
out JspWriter
request HttpServletRequest
response HttpServletResponse
config ServletConfig
application ServletContext
session HttpSession
pageContext PageContext
page Object
exception Throwable
1) out implicit object
For writing any data to the buffer, JSP provides an implicit object named out. It is the object of
JspWriter. In case of servlet you need to write:
1. PrintWriter out=response.getWriter();
But in JSP, you don't need to write this code.
Example of out implicit object
In this example we are simply displaying date and time.

index.jsp
1. <html>
2. <body>
3. <% out.print("Today is:"+java.util.Calendar.getInstance().getTime()); %>
4. </body>
5. </html>
Output
1.7. JSP DIRECTIVES
The jsp directives are messages that tells the web container how to translate a JSP page into the
corresponding servlet.
There are three types of directives:
• page directive
• include directive
• taglib directive
Syntax of JSP Directive
1. <%@ directive attribute="value" %>

1.7.1. JSP PAGE DIRECTIVE
The page directive defines attributes that apply to an entire JSP page.
Syntax of JSP page directive
1. <%@ page attribute="value" %>
Attributes of JSP page directive
• import
• contentType
• extends
• info
• buffer
• language
• isELIgnored
• isThreadSafe
• autoFlush
• session
• pageEncoding
• errorPage
• isErrorPage
1)import
The import attribute is used to import class,interface or all the members of a package.It is
similar to import keyword in java class or interface.
Example of import attribute
1. <html>
2. <body>
3.
4. <%@ page import="java.util.Date" %>
5. Today is: <%= new Date() %>
6.
7. </body>
8. </html>

2)contentType
The contentType attribute defines the MIME(Multipurpose Internet Mail Extension) type of the
HTTP response.The default value is "text/html;charset=ISO-8859-1".
Example of contentType attribute
1. <html>
2. <body>
3.
4. <%@ page contentType=application/msword %>
5. Today is: <%= new java.util.Date() %>
6.
7. </body>
8. </html>
3)extends
The extends attribute defines the parent class that will be inherited by the generated servlet.It
is rarely used.
4)info
This attribute simply sets the information of the JSP page which is retrieved later by using
getServletInfo() method of Servlet interface.
Example of info attribute
1. <html>
2. <body>
3.
4. <%@ page info="composed by Sonoo Jaiswal" %>
6.
7. </body>
8. </html>
The web container will create a method getServletInfo() in the resulting servlet.For example:
1. public String getServletInfo() {
2. return "composed by Sonoo Jaiswal";
3. }

5)buffer
The buffer attribute sets the buffer size in kilobytes to handle output generated by the JSP
page.The default size of the buffer is 8Kb.
Example of buffer attribute
1. <html>
2. <body>
3.
4. <%@ page buffer="16kb" %>
6.
7. </body>
8. </html>
6)language
The language attribute specifies the scripting language used in the JSP page. The default value is
"java".
7)isELIgnored
We can ignore the Expression Language (EL) in jsp by the isELIgnored attribute. By default its
value is false i.e. Expression Language is enabled by default. We see Expression Language
later.
1. <%@ page isELIgnored="true" %>//Now EL will be ignored
8)isThreadSafe
Servlet and JSP both are multithreaded.If you want to control this behaviour of JSP page, you
can use isThreadSafe attribute of page directive.The value of isThreadSafe value is true.If
you make it false, the web container will serialize the multiple requests, i.e. it will wait until
the JSP finishes responding to a request before passing another request to it.If you make the
value of isThreadSafe attribute like:
<%@ page isThreadSafe="false" %>
The web container in such a case, will generate the servlet as:
1. public class SimplePage_jsp extends HttpJspBase
2. implements SingleThreadModel{
3. .......

4. }
9)errorPage
The errorPage attribute is used to define the error page, if exception occurs in the current page,
it will be redirected to the error page.
Example of errorPage attribute
1. //index.jsp
2. <html>
3. <body>
4.
5. <%@ page errorPage="myerrorpage.jsp" %>
6.
7. <%= 100/0 %>
8.
9. </body>
10. </html>
10)isErrorPage
The isErrorPage attribute is used to declare that the current page is the error page.
Note: The exception object can only be used in the error page.
Example of isErrorPage attribute
1. //myerrorpage.jsp
2. <html>
3. <body>
4. <%@ page isErrorPage="true" %>
5. Sorry an exception occured!<br/>
6. The exception is: <%= exception %>
7. </body>
8. </html>

1.7.2. JSP INCLUDE DIRECTIVE
The include directive is used to include the contents of any resource it may be jsp file, html file
or text file. The include directive includes the original content of the included resource at page
translation time (the jsp page is translated only once so it will be better to include static
resource).
Advantage of Include directive
Code Reusability
Syntax of include directive
1. <%@ include file="resourceName" %>
Example of include directive
In this example, we are including the content of the header.html file. To run this example you
must create an header.html file.
1. <html>
2. <body>
3.
4. <%@ include file="header.html" %>
5.
6. Today is: <%= java.util.Calendar.getInstance().getTime() %>
7.
8. </body>
9. </html>
1.7.3. JSP TAGLIB DIRECTIVE
The JSP taglib directive is used to define a tag library that defines many tags. We use the TLD
(Tag Library Descriptor) file to define the tags. In the custom tag section we will use this tag so
it will be better to learn it in custom tag.
Syntax JSP Taglib directive
1. <%@ taglib uri="uriofthetaglibrary" prefix="prefixoftaglibrary" %>

Example of JSP Taglib directive
In this example, we are using our tag named currentDate. To use this tag we must specify the
taglib directive so the container may get information about the tag.
1. <html>
2. <body>
3.
4. <%@ taglib uri="http://www.javatpoint.com/tags" prefix="mytag" %>
5.
6. <mytag:currentDate/>
7.
8. </body>
9. </html>
1.8. EXCEPTION HANDLING IN JSP
The exception is normally an object that is thrown at runtime. Exception Handling is the process
to handle the runtime errors. There may occur exception any time in your web application. So
handling exceptions is a safer side for the web developer. In JSP, there are two ways to perform
exception handling:
1. By errorPage and isErrorPage attributes of page directive
2. By <error-page> element in web.xml file
Example of exception handling in jsp by the elements of page directive
In this case, you must define and create a page to handle the exceptions, as in the error.jsp
page. The pages where may occur exception, define the errorPage attribute of page directive,
as in the process.jsp page.
There are 3 files:
• index.jsp for input values
• process.jsp for dividing the two numbers and displaying the result
• error.jsp for handling the exception

index.jsp
1. <form action="process.jsp">
2. No1:<input type="text" name="n1" /><br/><br/>
3. No1:<input type="text" name="n2" /><br/><br/>
4. <input type="submit" value="divide"/>
5. </form>
process.jsp
1. <%@ page errorPage="error.jsp" %>
2. <%
3. String num1=request.getParameter("n1");
5. int a=Integer.parseInt(num1);
6. int b=Integer.parseInt(num2);
7. int c=a/b;
8. out.print("division of numbers is: "+c);
9. %>
error.jsp
1. <%@ page isErrorPage="true" %>
2. <h3>Sorry an exception occured!</h3>
3. Exception is: <%= exception %>
Output of this example:

Example of exception handling in jsp by specifying the error-page element in web.xml file
This approach is better because you don't need to specify the errorPage attribute in each jsp
page. Specifying the single entry in the web.xml file will handle the exception. In this case,
either specify exception-type or error-code with the location element. If you want to handle all
the exception, you will have to specify the java.lang.Exception in the exception-type element.
Let's see the simple example:
There are 4 files:
• web.xml file for specifying the error-page element
• index.jsp for input values
• process.jsp for dividing the two numbers and displaying the result
• error.jsp for displaying the exception
1) web.xml file if you want to handle any exception
1. <web-app>
2.
3. <error-page>
4. <exception-type>java.lang.Exception</exception-type>
5. <location>/error.jsp</location>

6. </error-page>
7.
8. </web-app>
This approach is better if you want to handle any exception. If you know any specific error code
and you want to handle that exception, specify the error-code element instead of exception-
type as given below:
1) web.xml file if you want to handle the exception for a specific error code
1. <web-app>
2.
3. <error-page>
4. <error-code>500</error-code>
5. <location>/error.jsp</location>
6. </error-page>
7.
8. </web-app>
2) index.jsp file is same as in the above example
3) process.jsp
Now, you don't need to specify the errorPage attribute of page directive in the jsp page.
1. <%@ page errorPage="error.jsp" %>
2. <%
3.
6.
7. int a=Integer.parseInt(num1);
8. int b=Integer.parseInt(num2);
9. int c=a/b;
10. out.print("division of numbers is: "+c);
11.
12. %>

1.9. JSP ACTION TAGS (ACTION ELEMENTS)
There are many JSP action tags or elements. Each tag is used to perform some specific tasks.
The action tags basically are used to control the flow between pages and to use Java Bean. Jsp
action tags are as follows:
• jsp:forward
• jsp:include
• jsp:useBean
• jsp:setProperty
• jsp:getProperty
• jsp:plugin
• jsp:param
• jsp:fallback
The jsp:useBean, jsp:setProperty and jsp:getProperty tags are used for bean development. So
we will see these tags in bean developement.
jsp:forward action tag
The jsp:forward action tag is used to forward the request to another resource it may be jsp,
html or another resource.
Syntax of jsp:forward action tag without parameter
1. <jsp:forward page="relativeURL | <%= expression %>" />
Syntax of jsp:forward action tag with parameter
1. <jsp:forward page="relativeURL | <%= expression %>">
2. <jsp:param name="parametername" value="parametervalue | <%=expression%>" />
3. </jsp:forward>
Example of jsp:forward action tag without parameter
In this example, we are simply forwarding the request to the printdate.jsp file.
index.jsp
1. <html>
2. <body>

3. <h2>this is index page</h2>
4.
5. <jsp:forward page="printdate.jsp" />
6. </body>
7. </html>
printdate.jsp
1. <html>
2. <body>
4. </body>
5. </html>
Example of jsp:forward action tag with parameter
In this example, we are forwarding the request to the printdate.jsp file with parameter and
printdate.jsp file prints the parameter value with date and time.
index.jsp
1. <html>
2. <body>
4. <jsp:forward page="printdate.jsp" >
5. <jsp:param name="name" value="javatpoint.com" />
6. </jsp:forward>
7. </body>
8. </html>
printdate.jsp
1. <html>
2. <body>
3.
5. <%= request.getParameter("name") %>
6.
7. </body>
8. </html>
jsp:include action tag

The jsp:include action tag is used to include the content of another resource it may be jsp, html
or servlet.
The jsp include action tag includes the resource at request time so it is better for dynamic
pagesbecause there might be changes in future.
Advantage of jsp:include action tag
code reusability
Syntax of jsp:include action tag without parameter
1. <jsp:include page="relativeURL | <%= expression %>" />
Syntax of jsp:include action tag with parameter
1. <jsp:include page="relativeURL | <%= expression %>">
2. <jsp:param name="parametername" value="parametervalue | <%=expression%>" />
3. </jsp:include>
Example of jsp:include action tag without parameter
In this example, index.jsp file includes the content of the printdate.jsp file.
File: index.jsp
1. <html>
2. <body>
4. <jsp:include page="printdate.jsp" />
5. <h2>end section of index page</h2>
6. </body>
7. </html>
File: printdate.jsp

1.10. JAVA BEAN
A Java Bean is a java class that should follow following conventions:
• It should have a no-arg constructor.
• It should be Serializable.
• It should provide methods to set and get the values of the properties, known as getter
and setter methods.
Simple example of java bean class
1. //Employee.java
2. package mypack;
3. public class Employee implements java.io.Serializable{
4. private int id;
5. private String name;
6. public Employee(){}
7.
8. public void setId(int id){this.id=id;}
9.
10. public int getId(){return id;}
11.
12. public void setName(String name){this.name=name;}
13.
14. public String getName(){return name;}
15.
16. }
How to access the java bean class?
To access the java bean class, we should use getter and setter methods.
1. package mypack;
2. public class Test{
3. public static void main(String args[]){
4. Employee e=new Employee();//object is created
5. e.setName("Arjun");//setting value to the object
6. System.out.println(e.getName());
7. }}

1.10.1. JSP:USEBEAN ACTION TAG
The jsp:useBean action tag is used to locate or instantiate a bean class. If bean object of the
Bean class is already created, it doesn't create the bean depending on the scope. But if object
of bean is not created, it instantiates the bean.
SYNTAX OF JSP:USEBEAN ACTION TAG
1. <jsp:useBean id= "instanceName" scope= "page | request | session | application"
2. class= "packageName.className" type= "packageName.className"
3. beanName="packageName.className | <%= expression >" >
4. </jsp:useBean>
Attributes and Usage of jsp:useBean action tag
1. id: is used to identify the bean in the specified scope.
2. scope: represents the scope of the bean. It may be page, request, session or application.
The default scope is page.
o page: specifies that you can use this bean within the JSP page. The default scope
is page.
o request: specifies that you can use this bean from any JSP page that processes
the same request. It has wider scope than page.
o session: specifies that you can use this bean from any JSP page in the same
session whether processes the same request or not. It has wider scope than
request.
o application: specifies that you can use this bean from any JSP page in the same
application. It has wider scope than session.
3. class: instantiates the specified bean class (i.e. creates an object of the bean class) but it
must have no-arg or no constructor and must not be abstract.
4. type: provides the bean a data type if the bean already exists in the scope. It is mainly
used with class or beanName attribute. If you use it without class or beanName, no
bean is instantiated.
5. beanName: instantiates the bean using the java.beans.Beans.instantiate() method.
Simple example of jsp:useBean action tag
In this example, we are simply invoking the method of the Bean class.
For the example of setProperty, getProperty and useBean tags, visit next page.

Calculator.java (a simple Bean class)
1. package com.javatpoint;
2. public class Calculator{
3. public int cube(int n){return n*n*n;}
4. }
index.jsp file
1. <jsp:useBean id="obj" class="com.javatpoint.Calculator"/>
2.
3. <%
4. int m=obj.cube(5);
5. out.print("cube of 5 is "+m);
6. %>

1.11. JSTL (JSP STANDARD TAG LIBRARY)
The JSP Standard Tag Library (JSTL) represents a set of tags to simplify the JSP development.
Advantage of JSTL
1. Fast Developement JSTL provides many tags that simplifies the JSP.
2. Code Reusability We can use the JSTL tags in various pages.
3. No need to use scriptlet tag It avoids the use of scriptlet tag.
There JSTL mainly provides 5 types of tags:
Tag Name Description
core tags The JSTL core tag provide variable support, URL management, flow
control etc. The url for the core tag is http://java.sun.com/jsp/jstl/core .
The prefix of core tag is c.
sql tags The JSTL sql tags provide SQL support. The url for the sql tags
ishttp://java.sun.com/jsp/jstl/sql and prefix is sql.
xml tags The xml sql tags provide flow control, transformation etc. The url for
the xml tags is http://java.sun.com/jsp/jstl/xml and prefix is x.
internationalization
tags
The internationalization tags provide support for message formatting,
number and date formatting etc. The url for the internationalization
tags ishttp://java.sun.com/jsp/jstl/fmt and prefix is fmt.
functions tags The functions tags provide support for string manipulation and string
length. The url for the functions tags
is http://java.sun.com/jsp/jstl/functions and prefix is fn.
For creating JSTL application, you need to load jstl.jar file.

1.11.1. JSTL CORE TAGS
The JSTL core tags mainly provides 4 types of tags:
• miscellaneous tags: catch and out.
• url management tags: import, redirect and url.
• variable support tags: remove and set.
• flow control tags: forEach, forTokens, if and choose.
Syntax for defining core tags
1. <%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>
c:catch
It is an alternative apporach of global exception handling of JSP. It handles the exception and
doesn't propagate the exception to error page. The exception object thrown at runtime is
stored in a variable named var.
Example of c:catch
Let's see the simple example of c:catch.
2. <c:catch>
3. int a=10/0;
4. </c:catch>
c:out
It is just like JSP expression tag but it is used for exression. It renders data to the page.
Example of c:out
Let's see the simple example of c:out.
index.jsp
1. <form action="process.jsp" method="post">
2. FirstName:<input type="text" name="fname"/><br/>
3. LastName:<input type="text" name="lname"/><br/>
4. <input type="submit" value="submit"/>

5. </form>
process.jsp
2. First Name:<c:out value="${param.fname}"></c:out><br/>
3. Last Name:<c:out value="${param.lname}"></c:out>
c:import
It is just like jsp include but it can include the content of any resource either within server or
outside the server.
Example of c:import
Let's see the simple example of c:import to display the content of other site.
index.jsp
2. <h1>ABC.com</h1>
3. <hr/>
4. <c:import url="http://www.javatpoint.com"></c:import>
Example of c:import to display the source code
Let's see the simple example of c:import to display the source code of other site.
index.jsp
2. <h1>ABC.com</h1>
3. <hr/>
4. <c:import var="data" url="http://www.javatpoint.com"></c:import>
5.
6. <h2>Data is:</h2>
7. <c:out value="${data}"></c:out>
c:forEach
It repeats the nested body content for fixed number of times or over collection.
Example of c:forEach

Let's see the simple example of c:forEach.
2. <c:forEach var="number" begin="5" end="10">
3. <c:out value="${number}"></c:out>
4. </c:forEach>
c:if
It tests the condition.
Example of c:if
Let's see the simple example of c:if.
2. <c:set var="number" value="${200}">
3. <c:if test="${number<500}">
4. <c:out value="number is less than 500"></c:out>
5. </c:if>
c:redirect
It redirects the request to the given url.
2. <c:redirect url="http://www.javatpoint.com"></c:redirect>

1.11.2. CUSTOM TAGS IN JSP
Custom tags are user-defined tags. They eliminates the possibility of scriptlet tag and separates
the business logic from the JSP page.
The same business logic can be used many times by the use of costom tag.
Advantages of Custom Tags
The key advantages of Custom tags are as follows:
1. Eliminates the need of srciptlet tag The custom tags eliminates the need of scriptlet tag
which is considered bad programming approach in JSP.
2. Separation of business logic from JSP The custom tags separate the the business logic
from the JSP page so that it may be easy to maintain.
3. Reusability The custom tags makes the possibility to reuse the same business logic again
and again.
Syntax to use custom tag
There are two ways to use the custom tag. They are given below:
1. <prefix:tagname attr1=value1....attrn=valuen />
1. <prefix:tagname attr1=value1....attrn=valuen >
2. body code
3. </prefix:tagname>
JSP Custom Tag API
The javax.servlet.jsp.tagext package contains classes and interfaces for JSP custom tag API. The
JspTag is the root interface in the Custom Tag hierarchy.

JspTag interface
The JspTag is the root interface for all the interfaces and classes used in custom tag. It is a
marker interface.
Tag interface
The Tag interface is the sub interface of JspTag interface. It provides methods to perform action
at the start and end of the tag.

Fields of Tag interface
There are four fields defined in the Tag interface. They are:
Field Name Description
public static int EVAL_BODY_INCLUDE it evaluates the body content.
public static int EVAL_PAGE it evaluates the JSP page content after the custom tag.
public static int SKIP_BODY it skips the body content of the tag.
public static int SKIP_PAGE it skips the JSP page content after the custom tag.
Methods of Tag interface
The methods of the Tag interface are as follows:
Method Name Description
public void
setPageContext(PageContext pc)
it sets the given PageContext object.
public void setParent(Tag t) it sets the parent of the tag handler.
public Tag getParent() it returns the parent tag handler object.
public int doStartTag()throws
JspException
it is invoked by the JSP page implementation object. The
JSP programmer should override this method and define
the business logic to be performed at the start of the tag.
public int doEndTag()throws
JspException
it is invoked by the JSP page implementation object. The
JSP programmer should override this method and define
the business logic to be performed at the end of the tag.
public void release() it is invoked by the JSP page implementation object to
release the state.
IterationTag interface
The IterationTag interface is the sub interface of the Tag interface. It provides an additional
method to reevaluate the body.

Field of IterationTag interface
There is only one field defined in the IterationTag interface.
• public static int EVAL_BODY_AGAIN it reevaluates the body content.
Method of Tag interface
There is only one method defined in the IterationTag interface.
• public int doAfterBody()throws JspException it is invoked by the JSP page
implementation object after the evaluation of the body. If this method returns
EVAL_BODY_INCLUDE, body content will be reevaluated, if it returns SKIP_BODY, no
more body cotent will be evaluated.
TagSupport class
The TagSupport class implements the IterationTag interface. It acts as the base class for new
Tag Handlers. It provides some additional methods also.
Example of JSP Custom Tag
In this example, we are going to create a custom tag that prints the current date and time. We
are performing action at the start of tag.
For creating any custom tag, we need to follow following steps:
1. Create the Tag handler class and perform action at the start or at the end of the tag.
2. Create the Tag Library Descriptor (TLD) file and define tags
3. Create the JSP file that uses the Custom tag defined in the TLD file
Understanding flow of custom tag in jsp

1) Create the Tag handler class
To create the Tag Handler, we are inheriting the TagSupport class and overriding its
methoddoStartTag().To write data for the jsp, we need to use the JspWriter class.
The PageContext class provides getOut() method that returns the instance of JspWriter class.
TagSupport class provides instance of pageContext bydefault.
File: MyTagHandler.java
1. package com.javatpoint.sonoo;
2. import java.util.Calendar;
3. import javax.servlet.jsp.JspException;
4. import javax.servlet.jsp.JspWriter;
5. import javax.servlet.jsp.tagext.TagSupport;
6. public class MyTagHandler extends TagSupport{
7.
8. public int doStartTag() throws JspException {
9. JspWriter out=pageContext.getOut();//returns the instance of JspWriter
10. try{
11. out.print(Calendar.getInstance().getTime());//printing date and time using JspWriter
12. }catch(Exception e){System.out.println(e);}
13. return SKIP_BODY;//will not evaluate the body content of the tag
14. }
15. }
2) Create the TLD file
Tag Library Descriptor (TLD) file contains information of tag and Tag Hander classes. It must be
contained inside the WEB-INF directory.
File: mytags.tld
1. <?xml version="1.0" encoding="ISO-8859-1" ?>
2. <!DOCTYPE taglib

3. PUBLIC "-//Sun Microsystems, Inc.//DTD JSP Tag Library 1.2//EN"
4. "http://java.sun.com/j2ee/dtd/web-jsptaglibrary_1_2.dtd">
5.
6. <taglib>
7.
8. <tlib-version>1.0</tlib-version>
9. <jsp-version>1.2</jsp-version>
10. <short-name>simple</short-name>
11. <uri>http://tomcat.apache.org/example-taglib</uri>
12.
13. <tag>
14. <name>today</name>
15. <tag-class>com.javatpoint.sonoo.MyTagHandler</tag-class>
16. </tag>
17. </taglib>
3) Create the JSP file
Let's use the tag in our jsp file. Here, we are specifying the path of tld file directly. But it is
recommended to use the uri name instead of full path of tld file. We will learn about uri later.
It uses taglib directive to use the tags defined in the tld file.
File: index.jsp
1. <%@ taglib uri="WEB-INF/mytags.tld" prefix="m" %>
2. Current Date and Time is: <m:today/>
Output

1.11.3. ATTRIBUTES IN JSP CUSTOM TAG
There can be defined too many attributes for any custom tag. To define the attribute, you need
to perform two tasks:
• Define the property in the TagHandler class with the attribute name and define the
setter method
• define the attribute element inside the tag element in the TLD file
Example to use attribute in JSP Custom Tag
In this example, we are going to use the cube tag which return the cube of any given number.
Here, we are defining the number attribute for the cube tag. We are using the three file here:
• index.jsp
• CubeNumber.java
• mytags.tld
index.jsp
1. <%@ taglib uri="WEB-INF/mytags.tld" prefix="m" %>
2.
3. Cube of 4 is: <m:cube number="4"></m:cube>
CubeNumber.java
1. package com.javatpoint.taghandler;
2.
3. import javax.servlet.jsp.JspException;
4. import javax.servlet.jsp.JspWriter;
5. import javax.servlet.jsp.tagext.TagSupport;
6.
7. public class CubeNumber extends TagSupport{
8. private int number;
9.
10. public void setNumber(int number) {
11. this.number = number;
12. }
13.
14. public int doStartTag() throws JspException {
15. JspWriter out=pageContext.getOut();
16. try{
17. out.print(number*number*number);
18. }catch(Exception e){e.printStackTrace();}
19.

20. return SKIP_BODY;
21. }
22. }
mytags.tld
1. <?xml version="1.0" encoding="ISO-8859-1" ?>
2. <!DOCTYPE taglib
3. PUBLIC "-//Sun Microsystems, Inc.//DTD JSP Tag Library 1.2//EN"
4. "http://java.sun.com/j2ee/dtd/web-jsptaglibrary_1_2.dtd">
5.
6. <taglib>
7. <tlib-version>1.0</tlib-version>
8. <jsp-version>1.2</jsp-version>
9. <short-name>simple</short-name>
10. <uri>http://tomcat.apache.org/example-taglib</uri>
11. <description>A simple tab library for the examples</description>
12.
13. <tag>
14. <name>cube</name>
15. <tag-class>com.javatpoint.taghandler.CubeNumber</tag-class>
16. <attribute>
17. <name>number</name>
18. <required>true</required>
19. </attribute>
20. </tag>
21. </taglib>

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