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Custom Tags in JSP Pages

Stephanie Bodoff

The standard JSP tags for invoking operations on JavaBeans components and performing request dispatching simplify JSP page development and maintenance. JSP technology also provides a mechanism for encapsulating other types of dynamic functionality in custom tags, which are extensions to the JSP language. Custom tags are usually distributed in the form of a tag library, which defines a set of related custom tags and contains the objects that implement the tags.

Some examples of tasks that can be performed by custom tags include operations on implicit objects, processing forms, accessing databases and other enterprise services such as e-mail and directories, and performing flow control. JSP tag libraries are created by developers who are proficient at the Java programming language and expert in accessing data and other services, and are used by Web application designers who can focus on presentation issues rather than being concerned with how to access enterprise services. As well as encouraging division of labor between library developers and library users, custom tags increase productivity by encapsulating recurring tasks so that they can be reused across more than one application.

Tag libraries are receiving a great deal of attention in the JSP technology community. For more information about tag libraries and for pointers to some freely-available libraries, see

http://java.sun.com/products/jsp/taglibraries.html
 

In This Chapter

What Is a Custom Tag?

The Example JSP Pages

Using Tags

Declaring Tag Libraries

Making the Tag Library Implementation Available

Types of Tags

Defining Tags

Tag Handlers

Tag Library Descriptors

Simple Tags

Tags with Attributes

Tags with Bodies

Tags That Define Scripting Variables

Cooperating Tags

Examples

An Iteration Tag

A Template Tag Library

How Is a Tag Handler Invoked?

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This tutorial contains information on the 1.0 version of the Java Web Services Developer Pack.

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