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Chapter 3. Tag Libraries
| Goals |
After completing this chapter, the student will be able to
- make a simple custom tag.
- make a complex custom tag.
|
| Prerequisites |
In order to complete this chapter successfully, the student must understand
- JSP directives.
- how to construct a JSP.
- how to construct and call JavaBeans.
|
| Objectives |
The purpose of this chapter is to provide the student with the necessary information about tags and tag libraries. |
Tags provide another way for a JSP developer to separate the presentation of an application from the logic of the application. The implementation of a tag differs from the implementation of a JavaBean. A tag's class must implement methods unique to tag classes in order for the tag to be executed properly in the JSP. Also, the tags in an application require a tag library descriptor XML file that contains information about each of the tags. A tag class extends javax.servlet.jsp.tagext.TagSupport or javax.servlet.jsp.tagext.BodyTagSupport.
In a Java Server Page, a tag is initialized with a declaration that looks like this:
| <%@ taglib uri="WEB-INF/lib/tag_library_name.tld" prefix="prefix_name" %> |
The tag_library_name.tld, used in the declaration of the tag, is the name of the tag library that has the information about the tag called tag_name. In JBoss, the tag_library_name.tld must be located in the /WEB-INF/lib pathway in order to be located by the JBoss engine. To use a very simple tag in the JSP:
A tag can contain a body:
<prefix_name:tag_name>
this is called the body of the tag
</prefix_name:tag_name>
|
A tag can also have attributes:
<prefix_name:tag_name attributeOne="hey" />
|
Creating a simple tag class
- the class should extend javax.servlet.jsp.tagext.TagSupport
- should override the method called public int doStartTag() extends JspTagException {
- can override the method called public int doEndTag() extends JspTagException {
- usually does not need to override public void release()
SKIP_BODY versus EVAL_BODY_INCLUDE and SKIP_PAGE versus EVAL_PAGE
SKIP_BODY is returned at the end of doStartTag to tell the JSP to not output the content contained in the body of the tag. The EVAL_BODY_INCLUDE is returned at the end of the doStartTag if the content in the body of the tag should be outputted. The SKIP_PAGE is returned from the doEndTag to tell the JSP to skip the rest of the content of the JSP, while the EVAL_PAGE signifies that the JSP should evaluate the rest of the contents of the page. The default values returned are SKIP_BODY and EVAL_PAGE.
| doStartTag |
Called when the open tag is read in the JSP - returns either SKIP_BODY or EVAL_BODY_INCLUDE |
| doEndTag |
Called when the close tag is called in the JSP - returns either SKIP_PAGE or EVAL_PAGE |
| release |
Called when the JSP is finished with the tag - resets the state of the tag |
The tag library descriptor file
The tag library descriptor file helps a JSP map a tag to a Java class. It is an XML file with a .tld suffix.
Elements used in the .tld file to describe tags:
| taglib |
signifies that a tag library will be described - required |
| tlibversion |
the tag library version - required |
| jspversion |
the version of JSP that will be used |
| shortname |
the name of the tag library - required |
| uri |
the Uniform Resource Identifier for the tag library |
| info |
the comment tag for the developer |
| tag |
signifies that a tag located in the taglib will be described - see following table for elements of a tag |
Elements used in the tag tag:
| name |
the name of the tag - required |
| tagclass |
the path information to the tag's class - required |
| teiclass |
the path information of the subclass of TagExtraInfo - this is not discussed in this chapter |
| bodycontent |
specifies the content type of the tag - can be empty, JSP, or tagdependent - empty means that the tag has no body, JSP means that there is a body that can interpreted as JSP, and tagdependent means that the tag will interpret the body as non-JSP content |
| info |
for comments |
| attribute |
signifies that an attribute of the tag will be described - see following table |
Elements used in the attribute tag
| name |
the name of the attribute that the tag might need in the declaration - required |
| required |
boolean value to specify if the attribute is required - can be either true or false |
| rtexprvalue |
specifies if the attribute can take a scriptlet expression as a value, which allows the attribute's value to determined when the attribute is set - if this element is not specified, the value is false - can be either true or false |
(If you have not already done so, you can download this and other examples used in this course. Mac OS X or other UNIX users click here instead.)
Do this:
- Create the directory structure. Create a SimpleTag directory, then create the usual WEB-INF and classes, then create the directory structure that represents the package structure, which in this example is com.masslight.tagExampleClasses.
| code/Chapter3/SimpleTag |
SimpleTag
|
+-- tagExample.jsp (*)
|
+-- build.xml (*)
|
+-- WEB-INF
|
+-- web.xml (*)
|
+-- tagExampleLib.tld (*)
|
+-- classes
|
+-- com
|
+-- masslight
|
+-- tagExampleClasses
|
+-- HelloWorldTag.java (*)
(*) denotes a file |
- Create the JSP in the SimpleTag directory
| code/Chapter3/SimpleTag/tagExample.jsp |
<%@ page language="java" %>
<!-- declare the tag -->
<%@ taglib uri="WEB-INF/tagExampleLib.tld" prefix="greeter" %>
<html>
<body>
<!-- use the tag -->
<greeter:Hello/>
</body>
</html>
|
- Create the web.xml file in WEB-INF
| code/Chapter3/SimpleTag/WEB-INF/web.xml |
<?xml version="1.0" encoding="ISO-8859-1"?>
<!DOCTYPE web-app
PUBLIC "-//Sun Microsystems, Inc.//DTD Web Application 2.2//EN"
"http://java.sun.com/j2ee/dtds/web-app_2_2.dtd">
<web-app>
<taglib>
<taglib-uri>/WEB-INF/tagExampleLib.tld</taglib-uri>
<taglib-location>/WEB-INF/tagExampleLib.tld</taglib-location>
</taglib>
</web-app>
|
- Create the Java file in WEB-INF/classes/com/masslight/tagExampleClasses/
| code/Chapter3/SimpleTag/WEB-INF/classes/com/masslight/tagExampleClasses/HelloWorldTag.java |
package com.masslight.tagExampleClasses;
import javax.servlet.jsp.*;
import javax.servlet.jsp.tagext.*;
import java.io.*;
public class HelloWorldTag extends javax.servlet.jsp.tagext.TagSupport {
public int doStartTag() throws JspException {
try {
pageContext.getOut().print("Hello, World!");
} catch (Exception ex) {
throw new JspException("IO problems");
}
return SKIP_BODY;
}
}
|
- Create the tag library descriptor file in WEB-INF. This maps each tag used in tagExample.jsp to a specific Java class, which in this example is com.masslight.tagExampleClasses.HelloWorldTag.
| code/Chapter3/SimpleTag/WEB-INF/tagExampleLib.tld |
<?xml version="1.0" encoding="ISO-8859-1" ?>
<!DOCTYPE taglib
PUBLIC "-//Sun Microsystems, Inc.//DTD JSP Tag Library 1.1//EN"
"http://java.sun.com/j2ee/dtds/web-jsptaglib_1_1.dtd">
<taglib>
<tlibversion>1.0</tlibversion>
<jspversion>1.1</jspversion>
<shortname>utility</shortname>
<info>
A simple tag library for the examples
</info>
<tag>
<name>Hello</name>
<tagclass>com.masslight.tagExampleClasses.HelloWorldTag</tagclass>
<bodycontent>empty</bodycontent>
<info>
Print Hello World
</info>
</tag>
</taglib>
|
- Finally, add the build.xml file, which we will use to automate building and deploying the web application. build.xml goes in the root SimpleTag directory, next to the JSPs.
| code/Chapter3/SimpleTag/build.xml |
<project name="SimpleTag" default="dist" basedir=".">
<!-- set global properties for this build -->
<property environment="env"/>
<property name="top" value="."/>
<property name="src" value="."/>
<property name="build" value="build"/>
<property name="dist" value="dist"/>
<property name="war_dir" value="${dist}/lib"/>
<property name="war_file" value="${war_dir}/SimpleTag.war"/>
<property name="webinf" value="${top}/WEB-INF"/>
<property name="web.xml" value="${webinf}/web.xml"/>
<property name="classes" value="${webinf}/classes"/>
<property name="lib" value="${top}/WEB-INF/lib"/>
<property name="servlet.jar" value="${env.TOMCAT_HOME}/lib/servlet.jar"/>
<property name="deploy" value="${env.JBOSS_HOME}/deploy"/>
<target name="clean">
<!-- Delete our the ${build} and ${dist} directory trees -->
<delete dir="${build}"/>
<delete dir="${dist}"/>
<delete dir="${war_dir}"/>
</target>
<target name="init">
<!-- Create the build directory structure used by compile and dist -->
<mkdir dir="${build}"/>
<mkdir dir="${dist}"/>
<mkdir dir="${war_dir}"/>
</target>
<target name="compile" depends="init">
<!-- Compile the java code from ${src} into ${build} -->
<javac
srcdir="${top}/${src}"
destdir="${build}"
classpath="${servlet.jar}"/>
</target>
<target name="dist" depends="compile">
<!-- Put everything in a war file -->
<war warfile="${war_file}" webxml="${web.xml}">
<!-- include all JSPs in root level -->
<fileset dir="${top}/${src}">
<include name="*.jsp"/>
</fileset>
<!-- include all tag libraries in WEB-INF,
but not web.xml (that's handled separately) -->
<webinf dir="${webinf}">
<include name="*.tld"/>
</webinf>
<!-- include all compiled classes -->
<classes dir="${build}"/>
</war>
</target>
<target name="deploy">
<!-- Copy the war file to the JBoss deploy directory -->
<copy file="${war_file}" todir="${deploy}"/>
</target>
<target name="all" depends="clean,dist,deploy"/>
</project>
|
- Do not manually compile the Java files. Instead, use Ant to compile. Start at the root SimpleTag directory and call Ant with the compile argument. You should see output like this:
c:\j2ee\code\Chapter3\SimpleTag> ant compile
Buildfile: build.xml
init:
[mkdir] Created dir: C:\j2ee\code\Chapter3\SimpleTag\build
[mkdir] Created dir: C:\j2ee\code\Chapter3\SimpleTag\dist
[mkdir] Created dir: C:\j2ee\code\Chapter3\SimpleTag\dist\lib
compile:
[javac] Compiling 1 source file to C:\j2ee\code\Chapter3\SimpleTag\build
BUILD SUCCESSFUL
Total time: 2 seconds
|
- Do not manually create the .war distribution file. Instead, use Ant to create it.
c:\j2ee\code\Chapter3\SimpleTag> ant dist
Buildfile: build.xml
init:
dist:
[war] Building war: C:\j2ee\code\Chapter3\SimpleTag\dist\lib\SimpleTag.war
BUILD SUCCESSFUL
Total time: 2 seconds
|
- Do not manually copy the .war file into your JBoss deploy directory. Instead, use Ant to deploy it.
c:\j2ee\code\Chapter3\SimpleTag> ant deploy
Buildfile: build.xml
deploy:
[copy] Copying 1 file to C:\j2ee\jboss\deploy
BUILD SUCCESSFUL
Total time: 0 seconds
|
- Test the application at http://localhost:8080/SimpleTag/tagExample.jsp
Why Ant rocks
It doesn't look like Ant is much better than doing things manually, but's only because we intentionally did each step we could see what it looked like. In fact, Ant can easily combine steps, by specifying in the build.xml file that a particular step requires other steps to be performed in succession:
| <target name="all" depends="clean,dist,deploy"/> |
And you execute it like this:
c:\j2ee\code\Chapter3\SimpleTag> ant all
Buildfile: build.xml
clean:
[delete] Deleting directory C:\j2ee\code\Chapter3\SimpleTag\build
[delete] Deleting directory C:\j2ee\code\Chapter3\SimpleTag\dist
init:
[mkdir] Created dir: C:\j2ee\code\Chapter3\SimpleTag\build
[mkdir] Created dir: C:\j2ee\code\Chapter3\SimpleTag\dist
[mkdir] Created dir: C:\j2ee\code\Chapter3\SimpleTag\dist\lib
compile:
[javac] Compiling 1 source file to C:\j2ee\code\Chapter3\SimpleTag\build
dist:
[war] Building war: C:\j2ee\code\Chapter3\SimpleTag\dist\lib\SimpleTag.war
deploy:
[copy] Copying 1 file to C:\j2ee\jboss\deploy
all:
BUILD SUCCESSFUL
Total time: 2 seconds
|
Voila! A completely clean compile and deployment in one easy step!
Output of SimpleTag application
Attributes must be declared in the tag library descriptor, set as a class wide variable in the tag class with an accessor that uses the same name as declared in the tag library descriptor, and if the attribute is required, given a value when the tag is initialized in the JSP. If the tag in the tag library descriptor looked like this:
<tag>
<name>exampleTagName</name>
<tagclass>com.masslight.tags.ExampleTag</tagclass>
<bodycontent>empty</bodycontent>
<info>This is an example tag to demonstrate how attributes work</info>
<attribute>
<name>attributeOne</name>
<required>true</required>
</attribute>
<attribute>
<name>attributeTwo</name>
<required>false</required>
</attribute>
</tag>
|
then the class would need to include the following code:
public class ExampleTag extends TagSupport {
int attributeOne = 0;
String attributeTwo = 0;
....
....
public void setAttributeOne(String tempAttributeOne) {
attributeOne = Integer.valueOf(tempAttributeOne).intValue();
}
public void setAttributeTwo(String tempAttributeTwo) {
attributeTwo = tempAttributeTwo;
}
....
....
|
and the JSP might look something like this - remember that attributeTwo was not required:
<%@ taglib uri="WEB-INF/lib/tagLibraryName.tld" prefix="example" %>
<example:exampleTagName attributeOne="1"/>
|
Do this:
- Create the directory structure. Create an AttributeTag directory, then WEB-INF, classes, and the directory structure com/masslight/tagExampleClasses.
| code/Chapter3/AttributeTag |
AttributeTag
|
+-- tagExample.jsp (*)
|
+-- build.xml (*)
|
+-- WEB-INF
|
+-- web.xml (*)
|
+-- tagExampleLib.tld (*)
|
+-- classes
|
+-- com
|
+-- masslight
|
+-- tagExampleClasses
|
+-- GreetingAttributeTag.java (*)
(*) denotes a file |
- Create the JSP in the AttributeTag directory.
| code/Chapter3/AttributeTag/tagExample.jsp |
<%@ page language="java" %>
<%@ taglib uri="WEB-INF/tagExampleLib.tld" prefix="greeter" %>
<html>
<body>
<greeter:Greeting greeting="Hey" />
</body>
</html>
|
- Create the web.xml file in WEB-INF
| code/Chapter3/AttributeTag/WEB-INF/web.xml |
<?xml version="1.0" encoding="ISO-8859-1"?>
<!DOCTYPE web-app
PUBLIC "-//Sun Microsystems, Inc.//DTD Web Application 2.2//EN"
"http://java.sun.com/j2ee/dtds/web-app_2_2.dtd">
<web-app>
<taglib>
<taglib-uri>
</taglib-uri>
<taglib-location>
</taglib-location>
</taglib>
</web-app>
|
- Create the Java file in WEB-INF/classes/com/masslight/tagExampleClasses/
| code/Chapter3/AttributeTag/WEB-INF/classes/com/masslight/tagExampleClasses/GreetingAttributeTag.java |
package com.masslight.tagExampleClasses;
import javax.servlet.jsp.*;
import javax.servlet.jsp.tagext.*;
import java.io.*;
public class GreetingAttributeTag extends javax.servlet.jsp.tagext.TagSupport {
public String greeting = "Hello";
public int doStartTag() throws JspTagException {
try {
pageContext.getOut().print(greeting);
} catch (Exception ex) {
throw new JspTagException("IO problems");
}
return SKIP_BODY;
}
public void setGreeting(String newGreeting) {
greeting = newGreeting;
}
}
|
- Create the tag library descriptor file in WEB-INF
| code/Chapter3/AttributeTag/WEB-INF/tagExampleLib.tld |
<?xml version="1.0" encoding="ISO-8859-1" ?>
<!DOCTYPE taglib
PUBLIC "-//Sun Microsystems, Inc.//DTD JSP Tag Library 1.1//EN"
"http://java.sun.com/j2ee/dtds/web-jsptaglib_1_1.dtd">
<taglib>
<tlibversion>1.0</tlibversion>
<jspversion>1.1</jspversion>
<shortname>utility</shortname>
<info>
A simple tag library for the examples
</info>
<tag>
<name>Greeting</name>
<tagclass>com.masslight.tagExampleClasses.GreetingAttributeTag</tagclass>
<info>Print a greeting specified by the greeting attribute</info>
<bodycontent>empty</bodycontent>
<attribute>
<name>greeting</name>
<required>true</required>
</attribute>
</tag>
</taglib>
|
- Create the build.xml file in the root AttributeTag directory.
| code/Chapter3/AttributeTag/build.xml |
<project name="AttributeTag" default="dist" basedir=".">
<!-- set global properties for this build -->
<property environment="env"/>
<property name="top" value="."/>
<property name="src" value="."/>
<property name="build" value="build"/>
<property name="dist" value="dist"/>
<property name="war_dir" value="${dist}/lib"/>
<property name="war_file" value="${war_dir}/AttributeTag.war"/>
<property name="webinf" value="${top}/WEB-INF"/>
<property name="web.xml" value="${webinf}/web.xml"/>
<property name="classes" value="${webinf}/classes"/>
<property name="lib" value="${top}/WEB-INF/lib"/>
<property name="servlet.jar" value="${env.TOMCAT_HOME}/lib/servlet.jar"/>
<property name="deploy" value="${env.JBOSS_HOME}/deploy"/>
<target name="clean">
<!-- Delete our the ${build} and ${dist} directory trees -->
<delete dir="${build}"/>
<delete dir="${dist}"/>
<delete dir="${war_dir}"/>
</target>
<target name="init">
<!-- Create the build directory structure used by compile and dist -->
<mkdir dir="${build}"/>
<mkdir dir="${dist}"/>
<mkdir dir="${war_dir}"/>
</target>
<target name="compile" depends="init">
<!-- Compile the java code from ${src} into ${build} -->
<javac
srcdir="${top}/${src}"
destdir="${build}"
classpath="${servlet.jar}"/>
</target>
<target name="dist" depends="compile">
<!-- Put everything in a war file -->
<war warfile="${war_file}" webxml="${web.xml}">
<!-- include all JSPs in root level -->
<fileset dir="${top}/${src}">
<include name="*.jsp"/>
</fileset>
<!-- include all tag libraries in WEB-INF,
but not web.xml (that's handled separately) -->
<webinf dir="${webinf}">
<include name="*.tld"/>
<exclude name="web.xml"/>
</webinf>
<!-- include all compiled classes -->
<classes dir="${build}"/>
</war>
</target>
<target name="deploy">
<!-- Copy the war file to the JBoss deploy directory -->
<copy file="${war_file}" todir="${deploy}"/>
</target>
<target name="all" depends="clean,dist,deploy"/>
</project>
|
- ant all to compile, jar, and deploy. You should see output like this:
C:\work\j2ee\code\Chapter3\AttributeTag> ant all
Buildfile: build.xml
clean:
init:
[mkdir] Created dir: C:\work\j2ee\code\Chapter3\AttributeTag\build
[mkdir] Created dir: C:\work\j2ee\code\Chapter3\AttributeTag\dist
[mkdir] Created dir: C:\work\j2ee\code\Chapter3\AttributeTag\dist\lib
compile:
[javac] Compiling 1 source file to C:\work\j2ee\code\Chapter3\AttributeTag\build
dist:
[war] Building war: C:\work\j2ee\code\Chapter3\AttributeTag\dist\lib\AttributeTag.war
deploy:
[copy] Copying 1 file to C:\j2ee\jboss\deploy
all:
BUILD SUCCESSFUL
Total time: 8 seconds
|
- Go to http://localhost:8080/AttributeTag/tagExample.jsp to test your application
It is important to note that pageContext, session, and application objects can be accessed from a tag class. This means that attributes from any and all of the different scopes can be used in a tag class.
Creating a complex tag class
- the class should extend javax.servlet.jsp.tagext.BodyTagSupport
- should override the method called public int doStartTag() throws JspTagException {
- can override the method public void doInitBody() throws JspTagException {
- needs the method public int doAfterBody() throws JspTagException {
- should override the method called public int doEndTag() throws JspTagException {
- does not need to override the public void release() method
- the bodycontent tag in the tag descriptor library should be JSP
The tag class that extends TagBody allows the developer to execute code before and after the body of the tag. Instead of returning SKIP_BODY or EVAL_BODY_INCLUDE, the doStartTag method returns SKIP_BODY or EVAL_BODY_TAG. The doAfterBody method returns either the SKIP_BODY or the EVAL_BODY_TAG which allows the tag to loop through the tag's body until some condition is met. The content of the tag's body can be accessed by a call to getBodyContent() which returns a BodyContent object. The developer needs to write the contents of the body to the output stream by making a call to the writeOut() method of the BodyContent object. To write out the content of the body, one must write out contents of the getPreviousOut() method. If the developer does not make this call, then nothing from the body of the tag will be shown. The doInitBody method returns void and is not such an important method as the doAfterBody method.
| doInitBody |
Called when the JSP enters the body of the tag - returns nothing |
| doAfterBody |
Called when the JSP leaves the body of the tag - returns SKIP_BODY or EVAL_BODY_TAG |
Do this:
- Create the directory structure. The root directory is named ComplexTag; the rest is the same as the previous examples.
- Create tagExample.jsp, RepeatHelloTag.java, web.xml, tagExampleLib.tld, and build.xml
| code/Chapter3/ComplexTag |
ComplexTag
|
+-- tagExample.jsp (*)
|
+-- build.xml (*)
|
+-- WEB-INF
|
+-- web.xml (*)
|
+-- tagExampleLib.tld (*)
|
+-- classes
|
+-- com
|
+-- masslight
|
+-- tagExampleClasses
|
+-- RepeatHelloTag.java (*)
(*) denotes a file |
| code/Chapter3/ComplexTag/tagExample.jsp |
<%@ page language="java" %>
<%@ taglib uri="WEB-INF/tagExampleLib.tld" prefix="greeter" %>
<html>
<body>
<greeter:RepeatHello>
Hello Again<br>
</greeter:RepeatHello>
</body>
</html>
|
| code/Chapter3/ComplexTag/WEB-INF/classes/com/masslight/tagExampleClasses/RepeatHelloTag.java |
package com.masslight.tagExampleClasses;
import javax.servlet.jsp.*;
import javax.servlet.jsp.tagext.*;
import java.io.*;
public class RepeatHelloTag extends javax.servlet.jsp.tagext.BodyTagSupport {
int count = 1;
int numberOfIterations = 3;
String greeting = new String("Hello <BR>");
public int doStartTag() throws JspTagException {
try {
pageContext.getOut().print(greeting);
} catch (Exception ex) {
throw new JspTagException("IO problems");
}
return EVAL_BODY_TAG;
}
public int doAfterBody() throws JspTagException {
try {
if (count < numberOfIterations) {
count++;
return EVAL_BODY_TAG;
}
else {
BodyContent bodyContent = getBodyContent();
bodyContent.writeOut(getPreviousOut());
return SKIP_BODY;
}
}
catch (Exception e) {
throw (new JspTagException("error"));
}
}
}
|
| code/Chapter3/ComplexTag/WEB-INF/web.xml |
<?xml version="1.0" encoding="ISO-8859-1"?>
<!DOCTYPE web-app
PUBLIC "-//Sun Microsystems, Inc.//DTD Web Application 2.2//EN"
"http://java.sun.com/j2ee/dtds/web-app_2_2.dtd">
<web-app>
<taglib>
<taglib-uri>/WEB-INF/tagExampleLib.tld</taglib-uri>
<taglib-location>/WEB-INF/tagExampleLib.tld</taglib-location>
</taglib>
</web-app>
|
| code/Chapter3/ComplexTag/WEB-INF/tagExampleLib.tld |
<?xml version="1.0" encoding="ISO-8859-1" ?>
<!DOCTYPE taglib
PUBLIC "-//Sun Microsystems, Inc.//DTD JSP Tag Library 1.1//EN"
"http://java.sun.com/j2ee/dtds/web-jsptaglib_1_1.dtd">
<taglib>
<tlibversion>1.0</tlibversion>
<jspversion>1.1</jspversion>
<shortname>utility</shortname>
<info>
A simple tag library for the examples
</info>
<tag>
<name>RepeatHello</name>
<tagclass>com.masslight.tagExampleClasses.RepeatHelloTag</tagclass>
<bodycontent>JSP</bodycontent>
<info>Print Hello Multiple Times</info>
</tag>
</taglib>
|
| code/Chapter3/ComplexTag/build.xml |
<project name="ComplexTag" default="dist" basedir=".">
<!-- set global properties for this build -->
<property environment="env"/>
<property name="top" value="."/>
<property name="src" value="."/>
<property name="build" value="build"/>
<property name="dist" value="dist"/>
<property name="war_dir" value="${dist}/lib"/>
<property name="war_file" value="${war_dir}/ComplexTag.war"/>
<property name="webinf" value="${top}/WEB-INF"/>
<property name="web.xml" value="${webinf}/web.xml"/>
<property name="classes" value="${webinf}/classes"/>
<property name="lib" value="${top}/WEB-INF/lib"/>
<property name="servlet.jar" value="${env.TOMCAT_HOME}/lib/servlet.jar"/>
<property name="deploy" value="${env.JBOSS_HOME}/deploy"/>
<target name="clean">
<!-- Delete our the ${build} and ${dist} directory trees -->
<delete dir="${build}"/>
<delete dir="${dist}"/>
<delete dir="${war_dir}"/>
</target>
<target name="init">
<!-- Create the build directory structure used by compile and dist -->
<mkdir dir="${build}"/>
<mkdir dir="${dist}"/>
<mkdir dir="${war_dir}"/>
</target>
<target name="compile" depends="init">
<!-- Compile the java code from ${src} into ${build} -->
<javac
srcdir="${top}/${src}"
destdir="${build}"
classpath="${servlet.jar}"/>
</target>
<target name="dist" depends="compile">
<!-- Put everything in a war file -->
<war warfile="${war_file}" webxml="${web.xml}">
<!-- include all JSPs in root level -->
<fileset dir="${top}/${src}">
<include name="*.jsp"/>
</fileset>
<!-- include all tag libraries in WEB-INF,
but not web.xml (that's handled separately) -->
<webinf dir="${webinf}">
<include name="*.tld"/>
<exclude name="web.xml"/>
</webinf>
<!-- include all compiled classes -->
<classes dir="${build}"/>
</war>
</target>
<target name="deploy">
<!-- Copy the war file to the JBoss deploy directory -->
<copy file="${war_file}" todir="${deploy}"/>
</target>
<target name="all" depends="clean,dist,deploy"/>
</project>
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- ant all to compile, jar, and deploy.
- Go to http://localhost:8080/ComplexTag/tagExample.jsp to test your application
Exercise 1. Fibonacci
Make an application that calculates the Fibonacci sequence with a tag that uses a repeating body. The application should produce the first n elements of the arithmetic sequence, using a tag that takes an attribute specifying the value of n. The actual element should be calculated using a JavaBean. The JavaBean method should be in the body of the tag. The tag would look something like this:
<arithmetic_sum:first_sequence numberOfElements = "7">
<%= bean.calculateElement() %>
</arithmetic_sum:first_sequence>
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