Writing the Object Model for the Listener and Component Tree Example - Java

This chapter gently introduces the JavaServer Faces technology. More importantly, it teaches you how to write your first JSF application to get a feel for how this great technology works. In addition to the sample chapters, this chapter prepares you for the next chapters by introducing the JSF Application Programming Interface (API) and the Application Configuration file. This excerpt comes from chapter two of JavaServer Faces Programming, by Budi Kurniawan (McGraw-Hill/Osborne, ISBN 0-07-222983-7, 2004).

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March 08, 2004

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For this application, you need a JavaBean to store the two numbers to add and the result of the addition. Listing 2 presents the JavaBean called NumberBean.

Listing 2 The NumberBean JavaBean

package ch02a; public class NumberBean { int firstNumber = 0; int secondNumber = 0; public NumberBean () { System.out.println("Creating NumberBean"); } public void setFirstNumber(int number) { firstNumber = number; System.out.println("setFirstNumber: " + number); } public int getFirstNumber() { System.out.println("getFirstNumber: " + firstNumber); return firstNumber; } public void setSecondNumber(int number) { secondNumber = number; System.out.println("setSecondNumber: " + number); } public int getSecondNumber() { System.out.println("getSecondNumber: " + secondNumber); return secondNumber; } public int getResult() { System.out.println("getResult " + (firstNumber + secondNumber)); return firstNumber + secondNumber; } }

Writing the Application Configuration File

As explained earlier in the chapter, the best way to make the JavaBean available to the JSF application is to register it in the application configuration file. Listing 3 shows the application configuration file (faces-config.xml) needed by the application.

Listing 3 The Application Configuration File (faces-config.xml) for the Listener and Component Tree Example

<?xml version="1.0"? > <!DOCTYPE faces-config PUBLIC "-//Sun Microsystems, Inc.//DTD JavaServer Faces Config 1.0//EN" "http://java.sun.com/dtd/web-facesconfig_1_0.dtd"> <faces-config> <managed-bean> <managed-bean-name>numberBean</managed-bean-name> <managed-bean-class>ch02a.NumberBean</managed-bean-class> <managed-bean-scope>session</managed-bean-scope> </managed-bean> </faces-config>

Authoring the JSP Page for the Listener and Component Tree Example

For the user interface, you need a JSP page called adder.jsp, which is shown in Listing 4.

Listing 4 The adder.jsp Page

<%@ taglib uri="http://java.sun.com/jsf/html" prefix="h" %><%@ taglib uri="http://java.sun.com/jsf/core" prefix="f" %><f:use_faces><h:form formName="addForm"> <%@ taglib uri="http://java.sun.com/jsf/html" prefix="h" %> <%@ taglib uri="http://java.sun.com/jsf/core" prefix="f" %> <html> <head> <title>Add 2 numbers</title> </head> <body> <f:use_faces> <h:form formName="addForm" > <br/>First Number: <h:input_number id="firstNumber" valueRef="numberBean.firstNumber"/> <br/>Second Number: <h:input_number id="secondNumber" valueRef="numberBean.secondNumber"/> <br/>Result: <h:output_number id="output" valueRef="NumberBean.result"/> <br/> <h:command_button id="submitButton" label="Add" commandName="submit" > <f:action_listener type="ch02a.MyActionListener" /> </h:command_button> </h:form> </f:use_faces> </body> </html>

Remember: This is part one of the second chapter of JavaServer Faces Programming, by Budi Kurniawan (McGraw-Hill/Osborne, ISBN 0-07-222983). Stay tuned for part 2 of "Introduction to JavaServer Faces," where we learn about JSP, JavaBeans, and Model 2.
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