Registering a Value-Change Listener on a Component (The Java EE 6 Tutorial)

The Java EE 6 Tutorial

Registering a Value-Change Listener on a Component

A ValueChangeListener implementation can be registered on a component that implements EditableValueHolder by nesting a valueChangeListener tag within the component’s tag on the page. The valueChangeListener tag supports the attributes shown in Table 8–3, one of which must be used.

Table 8–3 Attributes for the valueChangeListener Tag


Attribute	Description
`type`	References the fully qualified class name of a `ValueChangeListener` implementation. Can accept a literal or a value expression.
`binding`	References an object that implements `ValueChangeListener`. Can accept only a value expression, which must point to a backing bean property that accepts and returns a `ValueChangeListener` implementation.

The following example shows a value-change listener registered on a component:

<h:inputText id="name" size="50" value="#{cashier.name}"
     required="true">    
     <f:valueChangeListener type="listeners.NameChanged" />
</h:inputText>

In the example, the core tag type attribute specifies the custom NameChanged listener as the ValueChangeListener implementation registered on the name component.

After this component tag is processed and local values have been validated, its corresponding component instance will queue the ValueChangeEvent associated with the specified ValueChangeListener to the component.

The binding attribute is used to bind a ValueChangeListener implementation to a backing bean property. This attribute works in a similar way to the binding attribute supported by the standard converter tags.