Jspprogramming

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JSP – Java Server Page
Name :: Mallikarjuna G D
Reach me @ Training ::
Email :: gdmallikarjuna@gmail.com

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• It is referred as Java Server Pages and it is server side technology.
• Separates the graphical design from the dynamic content.
• It is helps to develop dynamic web applications
• It allows to insert java code within html pages
• it first converts to servlet to process the client request and it may be
referred as advanced technology of servlet.
What is JSP ?

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• Web designers can design and update pages without learning java
language.
• Programmers for java can write code without dealing with web page
design.
• Allows java to be embedded directly into an HTML page.
• Change in the code of JSP compiles automatically.
• Using custom tags and tag libraries length of code is reduced.
Benefits of JSP

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• In servlets,
- HTML code is printed from java code.
vs
• In JSP pages
- Java code is embedded in HTML code.
JAVA
Java
HTML
HTML
Relationships

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• JSP-enabled web server:
– picks up .jsp page
– parses it
– converts it to runnable form
– runs it.
• Converts page to a Java servlet (JspPage), with your code inside the
_jspService() method
– compiles it
– runs servlet protocol.
General Lines

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<%@ page language="java" contentType="text/html; charset=ISO-8859-1"
pageEncoding="ISO-8859-1"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="ISO-8859-1">
<title>Insert title here</title>
</head>
<body>
<form>
<% out.println("welcome to Jsp"); %>
</form>
</body>
</html>
Example

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JSP Request and Response Cycle
User
Request
Web Server
JSP Container
Execute Existing
Servlet
Servlet
Container
Compile
Servlet
Generate
Servlet
code
Execute
Servlet
File
Changed
Response
Response
No
Yes

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JSP Life Cycle
_jspService()
jspInit()
jspDestroy()
Request
Response
Phase Name Description
Page Translation The page is parsed and a java file containing the corresponding
servlet created.
Page Compilation The java file is compiled.
Load Class The compiled class is loaded.
Create instance An instance of the servlet is created.
Call jspInit() This method is called before any other method to allow
initialization.
Call _jspService() This method is called for each request
Call jspDestroy() Called when the servlet container decides to take the servlet out
of service.
• Has Seven phases.
• Slow in loading first time since it has to be translated into servlet, but becomes
subsequently faster.

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<H1>Current Date</H1>
<%= new Date()%>
public void _jspService(HttpServletRequest request,
HttpServletResponse response)
throws ServletException, IOException {
request.setContentType ("text/html");
HttpSession session = request.getSession (true);
JspWriter out = response.getWriter();
out.println("<H1>Current Date</H1>");
out.println (new Date());
...
}
Translation

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• Script language declarations, scriptlets, and expressions for including
Java fragments that embed dynamic content
• Standard directives guiding translation of a JSP page to a servlet
• Standard actions in the form of predefined JSP tags
• A portable tag extension mechanism, for building tag libraries—
effectively extending the JSP language
JSP Features

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• Code snippet
<!DOCTYPE html>
<html>
<head>
<title>Welcome to JSP World</title>
</head>
<body>
<form>
<% out.println("welcome to Jsp"); %>
</form>
</body>
</html>
Sample examples

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• JSP scripting elements lets you insert Java code into the servlet that
will be generated from the JSP page.
• There are three forms:
1. Expressions of the form <%= expression %> that are evaluated
and inserted into the output,
2. Scriplets of the form <% code %> that are inserted into the
servlet's service method, and
3. Declarations of the form <%! code %> that are inserted into the
body of the servlet class, outside of any existing methods
JSP Scripting Elements

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• A JSP expression is used to insert Java values directly into the output.
• It has the following form:
<%= Java Expression %>
• The Java expression is
– evaluated,
– converted to a string, and
– inserted into the page
– Not terminated by “ ; ”
• This evaluation is performed at runtime (when the page is requested),
and thus has full access to information about the request.
JSP Expressions

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• Code snippet
<%@page import="java.util.Date"%>
<html>
<head>
<title>welcome</title>
</head>
<body>
Current Date : <%=new Date()%>
</body>
</html>
Sample examples

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• The following predefined variables can be used:
– request, the HttpServletRequest.
– response, the HttpServletResponse.
– session, the HttpSession associated with the request (if any)
– out, the PrintWriter (a buffered version of type JspWriter) used to
send output to the client.
Predefined Variables

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• Code Snippet
pv_login.jsp
<%@ page language="java" contentType="text/html; charset=ISO-8859-1 pageEncoding="ISO-8859-1"%>
<% String path = request.getContextPath(); %>
<form name="pvform" method="post" action='<%=path%>/jsp/pv_usage.jsp'>
<Table>
<th bgcolor=red colspan=2> </th>
<tr> <td>Username</td> <td><input type="text" name="txtUsername"></td>
</tr>
<tr> <td>Password</td><td><input type="text" name="txtPassword"></td>
</tr>
</Table>
<input type="submit" value="submit">
</form>
</body>
</html>

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• Code Snippet
pv_usage.jsp
<!DOCTYPE html>
<html> <head> <meta charset="ISO-8859-1">
<title>JSP PREDEFINED VARIABLES</title> </head>
<body>
<%@ page import="java.util.Date"%>
<form name="pvForm" method="post" action="">
<h2>Predefined Expression Usage</h2>
<hr><UL>
<LI>CURRENT DATE TAND TIME() : <%=new Date()%></LI>
<LI>REQUEST PARAMETER Remote Host : <%=request.getRemoteHost()%></LI>
<LI>SESSION ID : <%=session.getId()%></LI>
<LI>REQUEST FROM PREVIOUS PAGE : <%=request.getParameter("txtUsername")%>
<LI>REQUEST FROM PREVIOUS PAGE : <%=request.getParameter("txtPassword")%>
</UL>
</form>
</body>
</html>

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• JSP scriptlets let you insert arbitrary code into the servlet method that
will be built to generate the page ( _jspService )
• Scriptlets have the following form:
<% Java Code %>
• Scriptlets have access to the same automatically defined variables as
expressions.
JSP Scriplets
• Scriplets produce output HTML by printing into the out variable
• Example:
<%
String queryData = request.getQueryString();
out.println ("Attached GET data: " + queryData);
%>

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HTML code before and after the scriplets is converted to print methods:
<% if (true) { %>
You <B>Are Rocking</B> the game!
<% } else { %>
Better <B>Luck </B> Next time!
<% } %>
if (true) {
out.println (" You <B>Are Rocking</B> the game! ");
}
else {
out.println (" Better <B>Luck </B> Next time! ");
}
HTML Code in Scriplets

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< %= calculate() %>
< % calculate(); % >
public void _jspService(HttpServletRequest request,
HttpServletResponse response)
throws ServletException, IOException {
request.setContentType ("text/html");
HttpSession session = request.getSession(true);
JspWriter out = response.getWriter();
out.println(calculate());
bar();
...
}
(Contd..)

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Example
<!DOCTYPE html>
<html>
<head>
<title>Scriptlet example</title>
</head>
<body>
<form name="usageScriptletFRM" id="usageScriptletFRM" method="post"
action="./usage_scriptlet.jsp">
<%
if (request.getParameter("hidCond") == null) {
%>

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(Contd..)
<table>
<th colspan="2">Login</th>
<tr>
<td>USER NAME ::</td>
<td><input type="text" name="txtUserName" id="txtUserName“ value=""></td>
</tr>
<tr>
<td>PASSWORD ::</td><td><input type="text" name="txtPassword" id="txtPassword“ value=""></td>
</tr>
<tr>
<td colspan='2'><input type="submit" value="submit"></td>
</tr>
<input type="hidden" name="hidCond" id="hidCond" value="true">
</table>
<%
} else {
String userName = request.getParameter("txtUserName");
String password = request.getParameter("txtPassword");
out.println("USERNAME :: " + userName + "PASSWORD ::" + password);
}
%>
</form>
</body>
</html>

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• A JSP declaration lets you define methods or fields that get inserted
into the main body of the servlet class (outside of the service method
processing the request)
• It has the following form:
<%! Variable or method %>
• Declarations do not produce output
JSP Declaration

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Code Snippet
<b>Declaration of Variable</b>
<%! int varCount=1000; %>
<%= "Value is:"+varCount %>
<br>
<b>Declaration of Method</b>
<%! int add(int firstNum, int secondNum){
return (firstNum+secondNum);
};
%>
<%= "Additional Value is:"+add(10,20) %>
</body>
JSP Declaration

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• As we have seen before, there are variables that can be used in the
code.
• There are eight automatically defined variables, sometimes called
implicit objects .
• The available variables are request, response, out, session, application,
config, pageContext, and page.

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<a href="./jsp/pre_implicit.jsp">Implicit objects</a>
Pre_implicit.jsp
<form name="pre_implicitFrm" id="pre_implicitFrm" method="post"
action="./implicitobjects.jsp">
<%
session.setAttribute("userSession", "Mallikarjuna");
pageContext.setAttribute("USER", "Mallik", PageContext.APPLICATION_SCOPE);
pageContext.setAttribute("PASSWORD", "Arjun", PageContext.REQUEST_SCOPE);
%>
<Table>
<caption>LOGIN ::</caption>
<th bgcolor=red colspan=2></th>
<tr><td>Username</td><td><input type="text" name="txtUsername"></td>
</tr>
<tr><td>Password</td><td><input type="text" name="txtPassword"></td>
</tr></Table>
<input type="submit" value="submit">
</form>
</body>
</html>
Code snippet

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<style>
table, th, td {
border: 1px solid black;
border-collapse: collapse;
}
<Table>
<caption>IMPLICIT OBJECTS ::</caption>
<tr><td>out</td><td>JspWriter</td><td><% out.print("Today is:"+java.util.Calendar.getInstance().getTime());
%></td></tr>
<tr><td>request</td><td>HttpServletRequest</td><td><%= request.getParameter("txtUsername") %></td></tr>
<tr><td>response</td><td>HttpServletResponse</td><td><a href="./implicit_send_redirect.jsp">Test
SendRedirect</a></td></tr>
<tr><td>session</td><td>HttpSession</td><td><%= (String)session.getAttribute("userSession") %></td></tr>
<tr><td>config</td><td>ServletConfig</td><td><a href="../sampleImplicitObj">Test Config</td></tr>
<tr><td>application</td><td>ServletContext</td><td><%= application.getInitParameter("DBConn") %></td></tr>
<tr><td>pageContext</td><td>pageContext</td><td><%=
(String)pageContext.getAttribute("USER",PageContext.APPLICATION_SCOPE) %></td></tr>
<tr><td>exception</td><td>Throwable</td><td><a href="./working_implicitobj.jsp">Test Error Page</a></td></tr>
</Table>
</body>
Code snippet

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implicit_send_redirect.jsp
<!DOCTYPE html>
<html>
<head>
<title>Insert title here</title>
</head>
<body>
<% response.sendRedirect("https://www.google.com"); %>
</body>
</html>
Code snippet

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web.xml
<servlet>
<servlet-name>sampleImplicitObj</servlet-name>
<jsp-file>/jsp/implicit_config.jsp</jsp-file>
<init-param>
<param-name>Driver</param-name>
<param-value>sun.jdbc.odbc.JdbcOdbcDriver</param-value>
</init-param>
</servlet>
<servlet-mapping>
<servlet-name>sampleImplicitObj</servlet-name>
<url-pattern>/sampleImplicitObj</url-pattern>
</servlet-mapping>
implicit_config.jsp
Implicit Config: <%= config.getInitParameter("Driver") %>
Code snippet

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working_implicitobj.jsp
<form action="./working.jsp">
Number1:<input type="text" name="first" >
Number2:<input type="text" name="second" >
<input type="submit" value="divide">
</form>
Working.jsp
<%@ page language="java" contentType="text/html; charset=ISO-8859-1" pageEncoding="ISO-8859-1"
errorPage="./error.jsp"%>
<%
String num1 = request.getParameter("first");
String num2 = request.getParameter("second");
// extracting numbers from request
int x = Integer.parseInt(num1);
int y = Integer.parseInt(num2);
int z = x / y; // dividing the numbers
out.print("division of numbers is: " + z); // result
%>
error.jsp
<%@ page isErrorPage="true" %>
h3>Sorry an exception occured!</h3> Exception is: <%= exception.getMessage() %>
Code snippet

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• This is the HttpServletRequest associated with the request
• It lets you
– look at the request parameters (via getParameter),
– the request type (GET, POST, HEAD, etc.), and
– the incoming HTTP headers (cookies, etc.)
request:
• This is the HttpServletResponse associated with the response to the
client
• The output stream is buffered,
• Thus, it is legal to set HTTP status codes and response headers, even
though this is not permitted in regular servlets once any output has
been sent to the client
response:
(Contd..)

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• This is the PrintWriter used to send output to the client.
• However, in order to make the response object useful, this is a
buffered version of PrintWriter called JspWriter.
• Note that you can adjust the buffer size, or even turn buffering off,
through use of the buffer attribute of the page directive.
out:
• This is the HttpSession object associated with the request
• Sessions are created automatically, so this variable is bound even if
there was no incoming session reference (unless session was turned
off using the session attribute of the page directive)
session:
(Contd..)

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• This is the ServletContext as obtained via getServletConfig().
getContext()
• Servlets and JSP pages can hold constant data in the ServletContext
object
• Getting and setting attributes is with getAttribute and setAttribute
• The ServletContext is shared by all the servlets in the server
application:
(Contd..)

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• JSP introduced a new class called PageContext.
• It encapsulate use of server-specific features like higher performance
JspWriters.
• The idea is that, if you access the server-specific features through this
class rather than directly, your code will still run on "regular"
servlet/JSP engines.
pageContext:
page:
• This is simply a synonym for this.
• page is not very useful in Java codes in JSP pages.
• It was created as a placeholder for the time when the scripting
language could be something other than Java.
(Contd..)

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• A JSP directive affects the overall structure of the servlet class that is
created from the JSP page
• It usually has the following form:
<%@ directive attribute="value" %>
• Multiple attribute settings for a single directive can be combined:
<%@ directive
attribute1="value1"
attribute2="value2"
...
attributeN="valueN" %>
JSP Directives

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• There are three main types of directive:
• page, which lets you do things like:
– import classes
– customize the servlet superclass
• include, which lets you:
– insert a file into the servlet class at the time the JSP file is
translated into a servlet
• taglib directive:
– indicates a library of custom tags that the page can include
(Contd..)

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The page directive lets you define the following attributes:
– import="package.class“
<%@ page import="java.util.*" %>
– contentType="MIME-Type"
<%@ page contentType="text/plain" %>
(it is the same as
<% response.setContentType("text/plain"); %>)
Page Directives

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• isThreadSafe=“true|false”
– Normal servlet processing or implementing SingleThreadModel
• session=“true|false”
– Allowing/disallowing sessions
• buffer=“sizekb|none”
– specifies the buffer size for the JspWriter out
• autoflush=“true|false”
– Flush buffer when full or throws an exception when buffer isfull
• extends=“package.class”
• info=“message”
– A message for the getServletInfo method
• errorPage=“url”
– Define a JSP page that handles uncaught exceptions
• isErrorPage=“true|false”
• language=“java”
(Contd..)

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• This directive lets you include files at the time the JSP page is
translated into a servlet.
• Content of the include file is parsed by the JSP at translation time.
• Includes a static file.
• The directive looks like this:
<%@ include file="relative url" %>
Include Directive

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We can replace the JSP tags with XML tags that represent
– Expressions
– Scriptles
– Declarations
– Directives
Writing JSP in XML
<%= Java Expression %>
<% Code %>
<%! declaration %>
<%@ directive %>
<jsp:expression>
Java Expression
</jsp:expression>
<jsp:scriptlet>
Code Java
</jsp:scriptlet>
<jsp:declaration>
Java Declaration
</jsp:declaration>
<jsp:directive.type
Attribute = value/>

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• JSP actions use constructs in XML syntax to control the behavior of
the servlet engine.
• You can
– dynamically insert a file,
– reuse JavaBeans components,
– forward the user to another page, or
– generate HTML for the Java plugin
Actions

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Actions
Available actions include:
– jsp:include :: Include a file at the time the page is requested.
– jsp:useBean :: Find or instantiate a Java Bean.
– jsp:setProperty:: Set the property of a JavaBean.
– jsp:getProperty:: Insert the property of a JavaBean into the output.
– jsp:forward :: Forward the requester to a new page .
– jsp:plugin :: Generate browser-specific code that makes an
OBJECT or EMBED tag for the Java plugin.

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• This action lets you insert files into the page being generated.
• The file inserted when page is requested
• The syntax looks like this:
<jsp:include page="relative URL"
flush="true" />
include Action

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• Forwards request to another page.
• Syntax: <jsp:forward page="relative URL"/>
• It has a single attribute, page, which should consist of a relative URL.
• This could be a static value, or could be computed at request time.
• Examples:
<jsp:forward page="/utils/errorReporter.jsp" />
<jsp:forward page="<%= someJavaExpression %>" />
forward Action

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• JavaBeans are reusable software components that can be manipulated
visually in a builder tool.
– Introspaction – analyze how the bean works
– Customization – the user can customize the look of the bean
– Events support
– Properties support
– Persistence – allowing saving the bean on a persistent mechanism
and loading it
Using Beans
• The bean Class should include a constructor with no arguments
• The bean class should not include public variables (fields)
• Access to the attributes of the bean is through methods that look like
– getName / setName for non-boolean fields
– isName / setName for boolean fields

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• This action lets you load in a JavaBean to be used in the JSP page.
• The simplest syntax for specifying that a bean should be used is:
<jsp:useBean id="name“
class="package.class" />
useBean Action
• Create an object of the given class.
• Bind the object to a variable with the given name.

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<jsp:useBean id=“db”
class=“dbiClasses.WebDatabase" />
<% dbiClasses.WebDatabase db = new
dbiClasses.WebDatabase(); %>
<jsp:useBean id=“handler“
class=“ConnectionHandler" type=“Runnable”/>
<% Runnable handler = new
ConnectionHandler(); %>
(Contd..)

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• Creating a Bean with jsp:useBean is like creating an object
• The scope of the bean can be beyond the page where it is declared
• Beans are used for resource collaboration
• Use jsp:getProperty to get a property of a bean
• Use the attributes name and property to get the requested property
<jsp:getProperty name=“db”
property=“login” />
<%= db.getLogin() %>
(Contd..)

3 December 2021 50
• Use jsp:setProperty to set a property of a bean.
• Use the attributes name, property and value to set the value to the
property.
<%= db.setLogin (“snoopy”); %>
<jsp:setProperty name=“db”
property=“login” value=“snoopy”/>
(Contd..)

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Example
package dbiTests;
public class SimpleBean {
private String message="No message specified";
public String getMessage() {
return(message);
}
public void setMessage(String message) {
this.message = message;
}
}

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(Contd..)
<HTML>
<HEAD> <TITLE>Reusing JavaBeans in JSP</TITLE>
</HEAD>
<BODY>
<CENTER> <TABLE BORDER=5>
<TR><TH CLASS="TITLE"> Reusing JavaBeans in JSP
</TABLE> </CENTER>
<P>
<jsp:useBean id="test" class=“dbiTest.SimpleBean" />
<jsp:setProperty name="test" property="message"
value="Hello WWW" />
<H1>Message: <I>
<jsp:getProperty name="test" property="message" />
</I></H1>
</BODY>
</HTML>

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property=“login”
value=‘<%=
request.getParameter (“login”)%>’
/>
Getting value from Request

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If we want the value of the parameter dblogin of the request will be set to
the bean db automatically we can use:
property=“login”
param=“dblogin” />
Getting Parameter Automatically
What will the following do?
property=“*” />
All Input Parameters:

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Sample-include
<%out.println("Welcome to " +request.getParameter("companyName")); %>
<jsp:forward page="welcome.jsp"></jsp:forward>
<jsp:include page="header.jsp" flush="true">
<jsp:param name="companyName" value=“E box training"/>
</jsp:include>
header.jsp
Forward in standard action

Jspprogramming

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