JAVASERVER FACES - Introduction to Java Programming: Comprehensive Version - page 1233

Three text input components along with their labels are placed in the grid panel (lines 11-24).
Four button components are placed in the grid panel (lines 26-35).
The bean property number1 is bound to the text input for Number 1 (line 15). The CSS
style text-align: right (line 14) specifies that the text is right-aligned in the input box.
The action attribute for the Add button is set to the add method in the calculator bean
(line 28). When the Add button is clicked, the add method in the bean is invoked to add
number1 with number2 and assign the result to result . Since the result property is bound
to the Result input text (line 23), the new result is now displayed in the text input field.

33.6 Session Tracking
You can create a managed bean at the application scope, session scope, view scope,
or request scope.

Key
Point

JSF supports session tracking using JavaBeans at the application scope, session scope, view
scope, and request scope. The scope is the lifetime of a bean. A request -scoped bean is alive
in a single HTTP request. After the request is processed, the bean is no longer alive. A view -
scoped bean lives as long as you are in the same JSF page. A session -scoped bean is alive
for the entire Web session between a client and the server. An application -scoped bean lives
as long as the Web application runs. In essence, a request-scoped bean is created once for a
request; a view-scoped bean is created once for the view; a session-scoped bean is created
once for the entire session; and an application-scoped bean is created once for the entire
application.
Consider the following example that prompts the user to guess a number. When the page starts,
the program randomly generates a number between 0 and 99 . This number is stored in a bean.
When the user enters a guess, the program checks the guess with the random number in the bean
and tells the user whether the guess is too high, too low, or just right, as shown in Figure 33.15.
Here are the steps to develop this project:

scope
request scope
view scope
session scope
application scope

Step 1. Create a new managed bean named guessNumber with the view scope as shown
in Listing 33.9, GuessNumberJSFBean.java.

create managed bean

Step 2. Create a JSF facelet in Listing 33.10, GuessNumber.xhtml.

create JSF facelet

L ISTING 33.9

GuessNumberJSFBean.java
1 package jsf2demo;
2
3 import javax.inject.Named;
4 import javax.faces.view.ViewScoped;
5
6 @Named(value = "guessNumber" )
7 @ViewScoped
8 public class GuessNumberJSFBean {
9

view scope

private int number; random number

guess by user

10 private String guessString;

11
12 public GuessNumberJSFBean() {
13 number = ( int )(Math.random() * 100 );
14 }
15
16

create random number

public String getGuessString() {

getter method

17 return guessString;

18 }
19
20

public void setGuessString(String guessString) {

setter method

21 this .guessString = guessString;

22 }