Session 37 - JSP - Part 2 (final)

Java & JEE Training
Session 37 – JSP Part 2 (Final)

Classification: Restricted
Agenda
• JSP vs Servlet
• LifeCycle of Servlet
• JSP Elements
• JSP Page directive
• Directives vs Action tags

Review of last session on JSP
• JSP vs Servlet
• Model1 vs Model 2 (MVC) architecture
• JSP Elements
• Declaration
• Expression
• Scriplets

Copyright @ 2000 Jordan Anastasiade. All rights reserved. 3
JSP vs Servlet
Servlet = HTML in a Java class
JSP = Java in an HTML page
out.println(“<h1> Hello World! </h1>”);
<%= request.getParameter("title") %>

Model 1 Architecture

Model 2 Architecture

LifeCycle of Servlet

JSP Elements
• Declarations <%! code %>
• Expressions <%= expression %>
• Scriptlets <% code %>

Directives -
page, include, taglib

JSP Page Directive
• Directives are messages to the JSP container and do not produce output
into the current output stream
• Syntax:
<%@ directive attribute=“value” %>
<%@ directive attribute1=“value1”
attribute1 =“value2” … %>
There are three types of directives:
1. page
2. include
3. taglib
XML form:
<jsp:directive.directiveType attribute=“value” />

Page Directive
• Defines attributes that apply to an entire JSP page.
<%@ page
[ language="java" ]
[ extends="package.class" ]
[ import="{package.class | package.*}, ..." ]
[ session="true|false" ]
[ buffer="none|8kb|sizekb" ]
[ autoFlush="true|false" ]
[ isThreadSafe="true|false" ]
[ info="text" ]
[ errorPage="relativeURL" ]
[ contentType="mimeType [ ;charset=characterSet ]" [
isErrorPage="true|false" ]
%>

Page directive example..
<%@ page import="java.util.*" %>
<HTML>
<BODY>
<%
System.out.println( "Evaluating date now" );
Date date = new Date();
%>
Hello! The time is now <%= date %>
</BODY>
</HTML>

Include Directive
• Includes a static file in a JSP file, parsing the file's JSP elements.
• Syntax
<%@ include file="relativeURL" %>
The <%@ include %> directive inserts a file of text or code in a JSP file at
translation time, when the JSP file is compiled.
<%@ include %> process is static. A static include means that the text
of the included file is added to the JSP file.
You may include a JSP or HTML file like this. E.g. for headers and
footers.

Include directive example…
• index.jsp
<html>
<head>
<title>Main JSP Page</title>
</head>
<body>
<%@ include file="file1.jsp" %>
Main JSP Page: Content between two include directives.
<%@ include file="file2.jsp" %>
</body>
</html>
• file1.jsp
<p align="center">
This is my File1.jsp and I will include it in index.jsp using include directive
</p>
• file2.jsp
<p align="center">
This is File2.jsp
</p>

Taglib Directive
• Defines a tag library and prefix for the custom tags used in the JSP page.
<%@ taglib uri="URIToTagLibrary" prefix="tagPrefix" %>
<%@ taglib uri="http://thathost/tags" prefix="public" %>
<public:loop>
</public:loop>
The <%@ taglib %> directive declares that the JSP file uses custom tags,
names the tag library that defines them, and specifies their tag prefix.
We will look into this further when we look at frameworks like Struts
and Spring.

JSP Action Tags:
include, forward, useBean

Directives vs Action tags
• Directives are used during translation phase while actions are used during
request processing phase.
• Unlike Directives, Actions are re-evaluated each time the page is accessed.

<jsp:include>
<html>
<head>
<title>Demo of JSP include Action Tag</title>
</head>
<body>
<h3>JSP page: Demo Include</h3>
<jsp:include page="sample.jsp" />
</body>
</html>

<jsp:include> with parameters
index.jsp
<html>
<head>
<title>JSP Include example with parameters</title>
</head>
<body>
<h2>This is index.jsp Page</h2>
<jsp:include page="display.jsp">
<jsp:param name="userid" value=“Pawan" />
<jsp:param name="password" value=“Pawan" />
<jsp:param name="name" value=“Pawan Kumar" />
<jsp:param name="age" value="27" />
</jsp:include>
</body>
</html>
display.jsp
<html>
<head>
<title>Display Page</title>
</head>
<body>
<h2>Hello this is a display.jsp Page</h2>
UserID: <%=request.getParameter("userid") %><br>
Password is: <%=request.getParameter("password")
%><br>
User Name: <%=request.getParameter("name")
%><br>
Age: <%=request.getParameter("age") %>
</body>
</html>

<jsp:forward> without parameters
• first.jsp
<html>
<head>
<title>Demo of JSP Forward Action Tag</title>
</head>
<body>
<h3>JSP page: Demo forward</h3>
<jsp:forward page="second.jsp" />
</body>
</html>

<jsp:forward> with parameters
index.jsp
<html>
<head>
<title>JSP Include example with parameters</title>
</head>
<body>
<h2>This is index.jsp Page</h2>
<jsp:forward page="display.jsp">
<jsp:param name="userid" value=“Pawan" />
<jsp:param name="password" value=“Pawan" />
<jsp:param name="name" value=“Pawan Kumar" />
<jsp:param name="age" value="27" />
</jsp:forward>
</body>
</html>
display.jsp
<html>
<head>
<title>Display Page</title>
</head>
<body>
<h2>Hello this is a display.jsp Page</h2>
UserID: <%=request.getParameter("userid") %><br>
Password is: <%=request.getParameter("password")
%><br>
User Name: <%=request.getParameter("name")
%><br>
Age: <%=request.getParameter("age") %>
</body>
</html>

<jsp:useBean> : Bean class
• First write a bean Details.java with username, age, password as properties.
public class Details {
public Details() {
}
private String username;
private int age;
private String password;
// Write getter and setter methods here…
}

<jsp:useBean> : index.jsp
<html>
<head><title>
useBean, getProperty and setProperty example
</title></head>
<form action="userdetails.jsp" method="post">
User Name: <input type="text" name="username"><br>
User Password: <input type="password" name="password"><br>
User Age: <input type="text" name="age"><br>
<input type="submit" value="register">
</form>
</html>

<jsp:useBean>: userDetails.jsp
<jsp:useBean id="userinfo“ class=“mypackage.Details">
</jsp:useBean>
<jsp:setProperty property="*" name="userinfo"/>
You have enterted below details:<br>
<jsp:getProperty property="username" name="userinfo"/><br>
<jsp:getProperty property="password" name="userinfo"/><br>
<jsp:getProperty property="age" name="userinfo" /><br>

Conclusion
JavaServer Pages (JSP) lets you separate the dynamic part of your pages
from the static HTML.
1. One can simply write the regular HTML in the normal manner, using
whatever Web-page-building tools you normally use.
2. One can enclose then the code for the dynamic parts in special tags,
most of which
start with "<%"
and end with "%>"

Topics to be covered in next session
• Core Java features with Examples
• Assertions
• Varargs
• Static import
• Autoboxing and Unboxing
• Enum
• Covariant
• Annotations
• Generics
• Instrumentation
• Catch Multiple Exceptions

Thank you!

Session 37 - JSP - Part 2 (final)

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Session 37 - JSP - Part 2 (final)