8 Copyright © 2005, Oracle. All rights reserved. Creating the Web Tier: JavaServer Pages.

8Copyright © 2005, Oracle. All rights reserved.

Creating the Web Tier: JavaServer Pages

8-2 Copyright © 2005, Oracle. All rights reserved.

Objectives

After completing this lesson, you should be able to do the following:

• Compare servlets and JavaServer Pages (JSP)

• Build a simple JSP

• Describe the JSP life cycle

• List the basic JSP elements

• Develop JSPs with declarations, expressions, and scriptlets

• List implicit objects

• Use JavaBeans with JSP


JavaServer Pages

Generates

Dynamic content

JSP

Connects to

EJB

Client

Request

Database

Response


Comparing Servlets and JSPs

Servlets:

• Are Java programs with embedded HTML

• Generate dynamic content

• Do not separate static and dynamic content

JavaServer Pages:

• Are HTML pages with embedded Java code or they can be pure XML

• Generate dynamic content

• Separate static and dynamic content


Invoking JSPs

HTML

JSP

Invoke

Servlet

JSP


The Date JSP

<%@ page contentType="text/html;charset=WINDOWS-1252"%><html> <head><meta http-equiv="Content-Type" content="text/html; charset=WINDOWS-1252"><title> Show Date </title></head><body><h2> The current time is: </h2><p> <%= new java.util.Date() %> </p></body></html>


The Date Servlet

...public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.setContentType(CONTENT_TYPE); PrintWriter out = response.getWriter(); out.println("<html>"); out.println("<head><title>Show Date </title></head><body><h2>The current time is:</h2><p>"); out.println(new java.util.Date()); out.println("</body></html>"); out.close(); }...


Automated JSP Features

• A JSP is automatically converted into a servlet the first time it is invoked:– Java source files are generated.– Java class files are generated.– The Java Just-In-Time compiler can be used.

• A JSP can contain extensible components:– Tags: Libraries such as OC4J JSP (OJSP) or

custom-developed tags.– JavaBeans (Beans are reused and their properties

are automatically introspected.)


JSP Life Cycle

http://host/date.jsp

J2EE container

Create servletdate.java

Compile servletdate.class

1

Servlet life cycle

Firsttime

Yes

2

3

No

OC4J


Basic JSP Elements

A JSP contains three main elements:

• Text elements

• Directives

• Scripting elements– Declarations– Expressions – Scriptlets


Declarations

• Are used to define methods or variables

• Begin with the sequence <%!• End with the sequence %>• Are inserted into the body of the servlet class

during translation

• Are used in conjunction with expressions or scriptlets

<%! private int i=3; %><%! private String a="Hello", b=" World"; %>


Expressions

• Begin with the sequence <%=• Contain Java expressions that are evaluated and

inserted into the servlet’s output

• End with the sequence %>• Do not end with a semicolon

<%= i+1 %><%= a + b %><%= new java.util.Date() %>

1

2


Scriptlets

• Begin with the sequence <%• Contain a block of Java code that is executed

every time a request is made

• End with the sequence %>

<% if (i<3) out.print("i<3"); if (i==3) out.print("i==3"); else out.print("i>3");%>


Implicit Objects

There are eight implicit objects, also known as predefined variables, in JSP:• request• response• session• out

• application• config• pageContext• page


Example


Directives

• Are used to set global values such as class declaration, method implementations, and so on

• Begin with the sequence <%@• End with the sequence %>• Are of the following types:

– page– include– taglib


include: Example


page Directive

You can define the following attributes by using the page directive:

• import• contentType• isThreadSafe• session• buffer• autoflush

• extends• info• errorPage• isErrorPage• language


JSP and JavaBeans

package lesson08;import java.lang.*;import java.util.*;public class LuckyNumberBean { private int luckyNum; public LuckyNumberBean() { luckyNum = (int) (1000 * Math.random()); } public int getLuckyNum() { return luckyNum; } public void setLuckyNum(int luckyNum) { this.luckyNum = luckyNum; }}


Using JavaBeans with JSP

Accessing JavaBeans with the <jsp:useBean> tag:

<jsp:useBean id="myBean" scope="session" class="lesson08.LuckyNumberBean" />


scope Attribute of <jsp:useBean> Tag

Client

Page 1 Page 2 Page 3

Request

Forward

Response

Request

Response

page scope page scope page scope

request scope request scope

session scope


Accessing and Setting Bean Property

• Accessing bean property:

• Setting bean property:

<jsp:getProperty name="myBean" property=“luckyNum" />

<jsp:setProperty name="myBean" property=“luckyNum" value="10" />


JSP XML Document

• Contains <jsp:root> as its root element

• Includes only XML syntax and does not include the traditional JSP tags

• Can be processed directly by the JSP container

• Can be used with XML development tools


Traditional Syntax Versus XML Syntax

Traditional: XML:

• No root element

• page directive<%@ page %>

• Declaration tag<%! %>

• Expression tag<%= expression %>

• Scriptlet<% %>

• <jsp:root> is the root element

• <jsp:directive.page />

• <jsp:declaration></jsp:declaration>

• <jsp:expression></jsp:expression>

• <jsp:scriptlet></jsp:scriptlet>


JDeveloper and JSPs

• Use the JSP Wizard in JDeveloper to create JSPs containing skeleton code.

• The structure pane helps to ensure that the JSP and HTML tags are properly formatted.

• Tag Insight automatically inserts end tags after starting a scriptlet.

• JSP code is automatically created and recompiled.• JDeveloper increases productivity while

debugging JSPs:– Automatically includes source Java files such as

your JavaBean source– Enables you to set breakpoints and watch

expressions in JSPs


Creating JSPs Visually


JSP Tag Insight


Summary

In this lesson, you should have learned how to:

• Differentiate between servlets and JSPs

• Build a simple JSP

• Describe the JSP life cycle

• Use JSP elements and implicit objects

• Develop JSPs with declarations, expressions, and scriptlets

• Use JavaBeans with JSP


Practices 8-1, 8-2, and 8-3: Overview

These practices cover the following topics:

• Creating a JSP that counts the occurrence of each character in a given string

• Using JavaBean to calculate an equal discount on the total amount of purchase

• Creating a JSP that displays product_id, product_name, and price in the form of a table

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