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These are:
– TagExtraInfo: Provides additional information, over and above that
contained within the TLD, about a custom tag.
– BeanInfo class: Tag handlers are themselves JavaBeans, and the Web
container will inspect them to obtain properties and methods. This can be
aided by a BeanInfo class for each tag handler.
The programmer downloads these files and puts them where they will be
available to the application. A directive is added to the JSP that refers to the
library and assigns it a prefix. In the JSP code, the prefix is used to invoke tags
within the library. The Web application deployment descriptor (web.xml) provides
the link between the directive used in the application and the actual JAR file
containing the classes that execute the function.
9.1.5 An inside look at a taglib
Let us take a look at a simple tag that displays a hello message. The elements of
a taglib include:
► An implementation bean
► A tag handler class
► A tag library descriptor
It is important to note that if you are simply using an existing taglib, the only thing
you really need to know is that these things exist. We want to show you a quick
example to take the mystery out of taglibs.
Implementation bean
The actual tag implementation is contained within a JavaBean called HelloBean,
shown in Example 9-1. The bean supplies one method, hello(), which accepts a
String argument. The method outputs a message.
Example 9-1 Simple custom tag example: HelloBean.java
//Simple custom tag example: HelloBean.java
package com.ibm.itso.j2eebook.tagexamples.beans;
/**
* JavaBean which displays a Hello message.
*
* @author: Adrian Spender
*/
public class HelloBean {
/**
* HelloBean default constructor.
280 IBM WebSphere Application Server - Express V5.0.2 Developer Handbook