WEB TECHNOLOGIES JSP

WEB TECHNOLOGIES JSP
Dr R Jegadeesan Prof-CSE
Jyothishmathi Institute of Technology and Science,
karimnagar

SYLLABUS
2
UNIT- IV JSP
The Anatomy of a JSP Page, JSP Processing, Declarations,
Directives, Expressions, Code Snippets, implicit objects,
Using Beans in JSP Pages, Using Cookies and session for
session tracking, connecting to database in JSP.

UNIT-IV : Introduction to JSP
Aim & Objective :
➢ Java server pages is a technology for developing web pages that
include dynamic content.
➢A JSP page can change its output based on variable items, identity of the
user, the browsers type and other information.
The Anatomy of JSP Page
3

4
Anatomy of a JSP page
The main parts are JSP elements and template texts.
<%@ page language="java" contentType="text/html" %>
<html>
<body bgcolor="white">
<jsp:useBean id = "userInfo" class= "com.ora.jsp.beans.userInfoBean"> <jsp:setProperty name="userInfo"
property="*"/>
</jsp:useBean>
The following information was saved:
<ul>
<li> User Name: <jsp:getProperty name="userInfo" property="userName"/>
<li> Email Address:
<jsp:getProperty name="userInfo" property="emailAddr"/> </ul>
</body>
</html>
The Anatomy of JSP Page

JSP Processing
5
The following steps explain how the web server creates the Webpage using JSP:
• As with a normal page, your browser sends an HTTP request to the web server
.
• The web server recognizes that the HTTP request is for a JSP page and forwards it to a JSP
engine. This is done by using the URL or JSP page which ends with .jsp instead of .html.
• The JSP engine loads the JSP page from disk and converts it into a servlet content. This
conversion is very simple in which all template text is converted to println( ) statements and all
JSP elements are converted to Java code. This code implements the corresponding dynamic
behavior of the page.
• The JSP engine compiles the servlet into an executable class and forwards the original request
to a servlet engine.
• A part of the web server called the servlet engine loads the Servlet class and executes it.
During execution, the servlet produces an output in HTML format. This output is further passed
on to the web server by the servlet engine inside an HTTP response

6
JSP Declarations:
A declaration declares one or more variables or methods that you can use in Java code later in the JSP
file. You must declare the variable or method before you use it in the JSP file.
Following is the syntax of JSP Declarations :
<%! declaration; [ declaration; ]+ ... %>
You can write XML equivalent of the above syntax as follows:
<jsp:declaration> code fragment </jsp:declaration>
Following is the simple example for JSP Declarations:
<%! int i = 0; %>
<%! int a, b, c; %>
<%! Circle a = new Circle(2.0); %>
JSP Declarations

7
JSP Directives:
JSP Directives: A JSP directive affects the overall structure of the servlet class.
It usually has the following form:
<%@ directive attribute="value" %>
There are three types of directive tags:
JSP Directives
Directive Description
<%@ page ... %> Defines page-dependent attributes, such as
scripting language, error page, and buffering
requirements
<%@ include ... %> Includes a file during the translation phase.
<%@ taglib ... %> Declares a tag library, containing custom
actions, used in the page

8
JSP Expressions:
A JSP expression element contains a scripting language expression that is evaluated, converted to a
String, and inserted where the expression appears in the JSP file. Because the value of an expression is
converted to a String, you can use an expression within a line of text, whether or not it is tagged with HTML,
in a JSP file. The expression element can contain any expression that is valid according to the Java
Language Specification but you cannot use a semicolon to end an expression.
Following is the syntax of JSP Expression:
<%= expression %>
You can write XML equivalent of the above syntax as follows:
<jsp:expression> expression </jsp:expression>
Following is the simple example for JSP Expression:
<html>
<head>
<title>A Comment Test</title>
</head>
<body>
<p> Today's date: <%= (new java.util.Date()).toLocaleString()%> </p> </body> </html>
This would generate following result: Today's date: 11-Sep-2010 21:24:25
JSP Expressions

9
JSP Implicit Objects
JSP Implicit Objects:
JSP supports nine automatically defined variables, which are also called implicit objects. These
variables are:
Objects Description
request This is the HttpServletRequest object associated with the request.
response This is the HttpServletResponse object associated with the response to
the client.
out This is the PrintWriter object used to send output to the client.
session This is the HttpSession object associated with the request.
application This is the ServletContext object associated with application context
config This is the ServletConfig object associated with the page.
pageContext This encapsulates use of server-specific features like higher
performance JspWriters.
page This is simply a synonym for this, and is used to call the methods
defined by the translated servlet class.

10
JSP- Java Beans
JSP- Java Bean
A JavaBean is a specially constructed Java class written in the Java and coded according to the
JavaBeans API specifications.
Following are the unique characteristics that distinguish a JavaBean from other Java classes −
• It provides a default, no-argument constructor
.
• It should be serializable and that which can implement the Serializable interface.
• It may have a number of properties which can be read or written.
•It may have a number of "getter" and "setter" methods for the properties. JavaBeans Properties
• A JavaBean property is a named attribute that can be accessed by the user of the object.
•The attribute can be of any Java data type, including the classes that you define.
• A JavaBean property may be read, write, read only, or write only. JavaBean properties are
accessed through two methods in the JavaBean's implementation class −

11
JSP- Java Beans
JSP- Java Bean
S.No. Method & Description
1 getPropertyName() For example, if property name is firstName, your method name
would be getFirstName() to read that property. This method is called accessor
.
2 setPropertyName() For example, if property name is firstName, your method name
would be setFirstName() to write that property. This method is called mutator
.
A read-only attribute will have only a getPropertyName() method, and a write- only attribute will
have only a setPropertyName() method.

12
JSP- Java Beans
Example Java beans with JSP
package com.tutorialspoint;
public class StudentsBean implements java.io.Serializable
{
private String firstName = null;
private String lastName = null;
private int age = 0;
public StudentsBean()
{ }
public String getFirstName()
{
return firstName;
}
public String getLastName()
{ return lastName; }
public int getAge(){ return age; }
public void setFirstName(String firstName)
{ this.firstName = firstName; }
public void setLastName(String lastName)
{ this.lastName = lastName; }
public void setAge(Integer age){ this.age = age; }
}

13
JSP- COOKIES
JSP- Cookies:
Cookies are text files stored on the client computer and they are kept for various information
tracking purposes. JSP transparently supports HTTP cookies using underlying servlet
technology.
There are three steps involved in identifying and returning users −
• Server script sends a set of cookies to the browser
. For example, name, age, or identification
number, etc.
•Browser stores this information on the local machine for future use.
•When the next time the browser sends any request to the web server then it sends those
cookies information to the server and server uses that
information to identify the user or may be for some other purpose as well.
• This chapter will teach you how to set or reset cookies, how to access them and how to
delete them using JSP programs.
The Anatomy of a Cookie :
•Cookies are usually set in an HTTP header (although JavaScript can also set a cookie
directly on a browser).

14
UNIT-IV Introduction to JSP
JSP- COOKIES
A JSP that sets a cookie might send headers that look something like this −
HTTP/1.1 200 OK
Date: Fri, 04 Feb 2000 21:03:38 GMT
Server: Apache/1.3.9 (UNIX) PHP/4.0b3
Set-Cookie: name = xyz;
expires = Friday, 04-Feb-07 22:03:38 GMT;
path = /; domain = tutorialspoint.com
Connection: close
Content-Type: text/html
As you can see, the Set-Cookie header contains a name value pair, a GMT date, a path and
a domain. The name and value will be URL encoded. The expires field is an instruction
to the browser to "forget" the cookie after the given time and date.

15
JSP- Sessions
JSP- Sessions:
Session Tracking HTTP is a "stateless" protocol which means each time a client retrieves a
Webpage, the client opens a separate connection to the Web server and the server automatically
does not keep any record of previous client request. Maintaining Session Between Web Client And
Server Let us now discuss a few options to maintain the session between the Web Client and the Web
Server − Cookies A webserver can assign a unique session ID as a cookie to each web client and for
subsequent requests from the client they can be recognized using the received cookie. This may not
be an effective way as the browser at times does not support a cookie. It is not recommended to use
this procedure to maintain the sessions. Hidden Form Fields A web server can send a hidden HTML
form field along with a unique session ID as follows −
<input type = "hidden" name = "sessionid" value = "12345">
This entry means that, when the form is submitted, the specified name and value are automatically
included in the GET or the POST data. Each time the web browser sends the request back, the
session_ id value can be used to keep the track of different web browsers. This can be an effective
way of keeping track of the session but clicking on a regular (<A HREF...>) hypertext link does not
result in a form submission, so hidden form fields also cannot support general session tracking. URL
Rewriting You can append some extra data at the end of each URL. This data identifies the session;
the server can associate that session identifier with the data it has stored about that session.

16
JSP- Sessions
JSP- Sessions:
For example,
with http://tutorialspoint.com/file.htm;sessionid=12345, the session identifier is attached as
sessionid = 12345 which can be accessed at the web server to identify the client.
URL rewriting is a better way to maintain sessions and works for the browsers when they don't
support cookies.
The drawback here is that you will have to generate every URL dynamically to assign a session ID
though page is a simple static HTML page.
The session Object Apart from the above mentioned options, JSP makes use of the servlet
provided HttpSession Interface.
This interface provides a way to identify a user across.

17
JSP- Sessions
JSP- Sessions:
• a one page request or
•visit to a website or
• store information about that user
.
By default, JSPs have session tracking enabled and a new HttpSession object is instantiated for
each new client automatically.
Disabling session tracking requires explicitly turning it off by setting the page directive session
attribute to false as follows −
<%@ page session = "false" %>
The JSP engine exposes the HttpSession object to the JSP author through the implicit session
object.
Since session object is already provided to the JSP programmer, the programmer can
immediately begin storing and retrieving data from the object without any initialization or
getSession().

18
JSP- Sessions
JSP- Sessions:
Session Tracking Example :
This example describes how to use the HttpSession object to find out the creation time and the
last-accessed time for a session. We would associate a new session with the request if one does
not already exist.
<%@ page import = "java.io.*,java.util.*" %>
<%
// Get session creation time.
Date createTime = new Date(session.getCreationTime()); // Get last access time of this
Webpage.
Date lastAccessTime = new Date(session.getLastAccessedTime());
String title = "Welcome Back to my website";
Integer visitCount = new Integer(0);
String visitCountKey = new String("visitCount");
String userIDKey = new String("userID");
String userID = new String("ABCD");

// Check if this is new comer on your Webpage.
if (session.isNew() ){
title = "Welcome to my website";
session.setAttribute(userIDKey, userID);
session.setAttribute(visitCountKey, visitCount);
}
visitCount = (Integer)session.getAttribute(visitCountKey);
visitCount = visitCount + 1;
userID = (String)session.getAttribute(userIDKey);
%>
<html>
<head>
<title>Session Tracking</title>
</head>
JSP- Sessions
19

// Check if this is new comer on your Webpage.
if (session.isNew() ){
title = "Welcome to my website";
session.setAttribute(userIDKey, userID);
}
visitCount = (Integer)session.getAttribute(visitCountKey);
visitCount = visitCount + 1;
userID = (String)session.getAttribute(userIDKey);
%>
<html>
<head>
<title>Session Tracking</title>
</head>
JSP- Sessions
20

<body>
<center>
<h1>Session Tracking</h1>
</center>
<table border = "1" align = "center">
<tr bgcolor = "#949494">
<th>Session info</th>
<th>Value</th>
</tr>
<tr> <td>id</td>
<td><% out.print( session.getId()); %></td> </tr>
<tr> <td>Creation Time</td>
<td><% out.print(createTime); %></td> </tr>
<tr> <td>Time of Last Access</td>
<td><% out.print(lastAccessTime); %></td> </tr>
<tr> <td>User ID</td>
<td><% out.print(userID); %></td></tr>
<tr> <td>Number of visits</td>
<td><% out.print(visitCount); %></td> </tr>
</table>
</body>
</html>
JSP- Sessions
21

JSP- Sessions
22
JSP–universities & Important Questions:
1. What is JSP
2. What are advantages of JSP
3. What is the difference between include directive & jsp:include
4. What are Custom tags. Why do you need Custom tags. How do you create Custom tag
5. What is jsp:usebean. What are the scope attributes & difference between these attributes
6. What is difference between scriptlet and expression
7. What is Declaration?

WEB TECHNOLOGIES JSP

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