Configuring a Bean

JavaServer Faces technology supports a sophisticated managed bean creation facility, which allows application architects to do the following:

• Configure simple beans and more complex trees of beans

• Initialize bean properties with values

• Place beans in a particular scope

• Expose the beans to the unified EL so that page authors can access them

An application architect configures the beans in the application configuration resource file. To learn how to configure a managed bean, see Configuring Beans. The managed bean configuration used by the Guess Number example is the following:

<managed-bean>
    <managed-bean-name>UserNumberBean</managed-bean-name>
    <managed-bean-class>
        guessNumber.UserNumberBean
    </managed-bean-class>
    <managed-bean-scope>session</managed-bean-scope>
    <managed-property>
        <property-name>minimum</property-name>
        <property-class>long</property-class>
        <value>0</value>
    </managed-property>
    <managed-property>
        <property-name>maximum</property-name>
        <property-class>long</property-class>
        <value>10</value>
    </managed-property>
</managed-bean>

The JavaServer Faces implementation processes this element on application startup time. When UserNumberBean is first referenced from the page, the JavaServer Faces implementation initializes it and sets the values of the properties, maximum and minimum. The bean is then stored in session scope if no instance exists. As such, the bean is available for all pages in the application.

A page author can then access the bean properties from the component tags on the page using the unified EL, as shown here:

<h:outputText value="#{UserNumberBean.minimum}"/>

The part of the expression before the . matches the name defined by the managed-bean-name element. The part of the expression after the . matches the name defined by the property-name element corresponding to the same managed-bean declaration.

Notice that the application configuration resource file does not configure the userNumber property. Any property that does not have a corresponding managed-property element will be initialized to whatever the constructor of the bean class has the instance variable set to. The next section explains more about using the unified EL to reference backing beans.

For more information on configuring beans using the managed bean creation Facility, see Configuring Beans.