Binding a Component Value to a Property

To bind a component’s value to a bean property, you specify the name of the bean and the property using the value attribute. As explained in Backing Beans, the value expression of the component tag’s value attribute must match the corresponding managed bean declaration in the application configuration resource file.

This means that the name of the bean in the value expression must match the managed-bean-name element of the managed bean declaration up to the first period (.) in the expression. Similarly, the part of the value expression after the period must match the name specified in the corresponding property-name element in the application configuration resource file.

For example, consider this managed bean configuration, which configures the ImageArea bean corresponding to the North America part of the image map on the chooselocale.jsp page of the Duke’s Bookstore application:

<managed-bean>
    <managed-bean-name> NA </managed-bean-name>
    <managed-bean-class> model.ImageArea </managed-bean-class>
    <managed-bean-scope> application </managed-bean-scope>
    <managed-property>
        <property-name>shape</property-name>
        <value>poly</value>
    </managed-property>
    <managed-property>
        <property-name>alt</property-name>
        <value>NAmerica</value>
    </managed-property>
    ...
</managed-bean>

This example configures a bean called NA, which has several properties, one of which is called shape.

Although the area tags on the chooselocale.jsp page do not bind to an ImageArea property (they bind to the bean itself), to do this, you refer to the property using a value expression from the value attribute of the component’s tag:

<h:outputText value="#{NA.shape}" />

Much of the time you will not include definitions for a managed bean’s properties when configuring it. You need to define a property and its value only when you want the property to be initialized with a value when the bean is initialized.

If a component tag’s value attribute must refer to a property that is not initialized in the managed-bean configuration, the part of the value-binding expression after the period must match the property name as it is defined in the backing bean.

See Application Configuration Resource File for information on how to configure beans in the application configuration resource file.

Writing Bean Properties explains in more detail how to write the backing bean properties for each of the component types.