Document Information


Part I Introduction

1.  Overview

2.  Using the Tutorial Examples

Part II The Web Tier

3.  Getting Started with Web Applications

4.  Java Servlet Technology

5.  JavaServer Pages Technology

6.  JavaServer Pages Documents

7.  JavaServer Pages Standard Tag Library

8.  Custom Tags in JSP Pages

9.  Scripting in JSP Pages

10.  JavaServer Faces Technology

11.  Using JavaServer Faces Technology in JSP Pages

12.  Developing with JavaServer Faces Technology

13.  Creating Custom UI Components

Determining Whether You Need a Custom Component or Renderer

When to Use a Custom Component

When to Use a Custom Renderer

Component, Renderer, and Tag Combinations

Understanding the Image Map Example

Why Use JavaServer Faces Technology to Implement an Image Map?

Understanding the Rendered HTML

Understanding the JSP Page

Configuring Model Data

Summary of the Application Classes

Steps for Creating a Custom Component

Creating Custom Component Classes

Specifying the Component Family

Performing Encoding

Performing Decoding

Enabling Component Properties to Accept Expressions

Saving and Restoring State

Delegating Rendering to a Renderer

Creating the Renderer Class

Identifying the Renderer Type

Handling Events for Custom Components

Defining the Custom Component Tag in a Tag Library Descriptor

14.  Configuring JavaServer Faces Applications

15.  Internationalizing and Localizing Web Applications

Part III Web Services

16.  Building Web Services with JAX-WS

17.  Binding between XML Schema and Java Classes

18.  Streaming API for XML

19.  SOAP with Attachments API for Java

Part IV Enterprise Beans

20.  Enterprise Beans

21.  Getting Started with Enterprise Beans

22.  Session Bean Examples

23.  A Message-Driven Bean Example

Part V Persistence

24.  Introduction to the Java Persistence API

25.  Persistence in the Web Tier

26.  Persistence in the EJB Tier

27.  The Java Persistence Query Language

Part VI Services

28.  Introduction to Security in the Java EE Platform

29.  Securing Java EE Applications

30.  Securing Web Applications

31.  The Java Message Service API

32.  Java EE Examples Using the JMS API

33.  Transactions

34.  Resource Connections

35.  Connector Architecture

Part VII Case Studies

36.  The Coffee Break Application

37.  The Duke's Bank Application

Part VIII Appendixes

A.  Java Encoding Schemes

B.  About the Authors



Creating the Component Tag Handler

Now that you’ve created your component and renderer classes, you’re ready to define how a tag handler processes the tag representing the component and renderer combination. If you’ve created your own JSP custom tags before, creating a component tag handler should be easy for you.

In JavaServer Faces applications, the tag handler class associated with a component drives the render response phase of the JavaServer Faces life cycle. For more information on the JavaServer Faces life cycle, see The Life Cycle of a JavaServer Faces Page.

The first thing that the tag handler does is to retrieve the type of the component associated with the tag. Next, it sets the component’s attributes to the values given in the page. It then returns the type of the renderer (if there is one) to the JavaServer Faces implementation so that the component’s encoding can be performed when the tag is processed. Finally, it releases resources used during the processing of the tag.

The image map custom component includes two tag handlers: AreaTag and MapTag. To see how the operations on a JavaServer Faces tag handler are implemented, let’s take a look at MapTag.

The MapTag class extends UIComponentELTag, which supports jsp.tagext.Tag functionality as well as JavaServer Faces-specific functionality. UIComponentELTag is the base class for all JavaServer Faces tags that correspond to a component. Tags that need to process their tag bodies should instead subclass UIComponentBodyELTag.

Retrieving the Component Type

As explained earlier, the first thing MapTag does is to retrieve the type of the component. It does this by using the getComponentType operation:

    public String getComponentType() {
        return ("DemoMap");

The value returned from getComponentType must match the value configured for the component with the component-type element of the application’s application configuration resource file. Registering a Custom Component explains how to configure a component.

Setting Component Property Values

After retrieving the type of the component, the tag handler sets the component’s property values to those supplied as tag attributes values in the page. This section assumes that your component properties are enabled to accept expressions, as explained in Enabling Component Properties to Accept Expressions.

Getting the Attribute Values

Before setting the values in the component class, the MapTag handler first gets the attribute values from the page by means of JavaBeans component properties that correspond to the attributes. The following code shows the property used to access the value of the immediate attribute.

private javax.el.ValueExpression immediate = null;

public void setImmediate(javax.el.ValueExpression immediate)
    this.immediate = immediate;

As this code shows, the setImmediate method takes a ValueExpression object. This means that the immediate attribute of the map tag accepts value expressions.

Similarly, the setActionListener and setAction methods take MethodExpression objects, which means that these attributes accept method expressions. The following code shows the properties used to access the values of the actionListener and the action attributes

private javax.el.MethodExpression actionListener = null;

public void setActionListener(
    javax.el.MethodExpression actionListener) {
    this.actionListener = actionListener;
private javax.el.MethodExpression action = null;

public void setAction(javax.el.MethodExpression action) {
        this.action = action;
Setting the Component Property Values

To pass the value of the tag attributes to MapComponent, the tag handler implements the setProperties method. The way setProperties passes the attribute values to the component class depends on whether the values are value expressions or method expressions.

Setting Value Expressions on Component Properties

When the attribute value is a value expression, setProperties first checks if it is not a literal expression. If the expression is not a literal, setProperties stores the expression into a collection, from which the component class can retrieve it and resolve it at the appropriate time. If the expression is a literal, setProperties performs any required type conversion and then does one of the following:

  • If the attribute is renderer-independent, meaning that it is defined by the component class, then setProperties calls the corresponding setter method of the component class.

  • If the attribute is renderer-dependent, setProperties stores the converted value into the component’s map of generic renderer attributes.

The following piece of the MapTag handler’s setProperties method sets the renderer-dependent property, styleClass, and the renderer-independent property, immediate:

if (styleClass != null) {
    if (!styleClass.isLiteralText()) {
        map.setValueExpression("styleClass", styleClass);
    } else {
if (immediate != null) {
    if (!immediate.isLiteralText()) {
        map.setValueExpression("immediate", immediate);
    } else {
Setting Method Expressions on Component Properties

The process of setting the properties that accept method expressions is done differently depending on the purpose of the method. The actionListener attribute uses a method expression to reference a method that handles action events. The action attribute uses a method expression to either specify a logical outcome or to reference a method that returns a logical outcome, which is used for navigation purposes.

To handle the method expression referenced by actionListener, the setProperties method must wrap the expression in a special action listener object called MethodExpressionActionListener. This listener executes the method referenced by the expression when it receives the action event. The setProperties method then adds this MethodExpressionActionListener object to the list of listeners to be notified when the event of a user clicking on the map occurs. The following piece of setProperties does all of this:

if (actionListener != null) {
        new MethodExpressionActionListener(actionListener));

If your component fires value change events, your tag handler’s setProperties method does a similar thing, except it wraps the expression in a MethodExpressionValueChangeListener object and adds the listener using the addValueChangeListener method.

In the case of the method expression referenced by the action attribute, the setProperties method uses the setActionExpression method of ActionSource2 to set the corresponding property on MapComponent:

if (action != null) {

Providing the Renderer Type

After setting the component properties, the tag handler provides a renderer type (if there is a renderer associated with the component) to the JavaServer Faces implementation. It does this using the getRendererType method:

public String getRendererType() {return "DemoMap";}

The renderer type that is returned is the name under which the renderer is registered with the application. See Delegating Rendering to a Renderer for more information.

If your component does not have a renderer associated with it, getRendererType should return null. In this case, the renderer-type element in the application configuration file should also be set to null.

Releasing Resources

It’s recommended practice that all tag handlers implement a release method, which releases resources allocated during the execution of the tag handler. The release method of MapTag as follows:

public void release() {
    current = null;
    styleClass = null;
    actionListener = null;
    immediate = null;
    action = null;

This method first calls the UIComponentTag.release method to release resources associated with UIComponentTag. Next, the method sets all attribute values to null.