Package jakarta.faces.event

Annotation Type ListenerFor

@Retention(RUNTIME)
@Target(TYPE)
@Inherited
@Repeatable(ListenersFor.class)
public @interface ListenerFor

Classes tagged with this annotation are installed as listeners using the method Application.subscribeToEvent(java.lang.Class<? extends jakarta.faces.event.SystemEvent>, java.lang.Class<?>, jakarta.faces.event.SystemEventListener) or UIComponent.subscribeToEvent(java.lang.Class<? extends jakarta.faces.event.SystemEvent>, jakarta.faces.event.ComponentSystemEventListener) (depending on the circumstances, described below).

The default implementation must support attaching this annotation to UIComponent or Renderer classes. In both cases, the annotation processing described herein must commence during the implementation of any variant of Application.createComponent() and must complete before the UIComponent instance is returned from createComponent(). The annotation processing must proceed according to an algorithm semantically equivalent to the following.

  • If this annotation is not present on the class in question, no action must be taken.

    Determine the "target" on which to call subscribeToEvent.

    If the class to which this annotation is attached implements ComponentSystemEventListener and is a UIComponent instance, "target" is the UIComponent instance.

    If the class to which this annotation is attached implements ComponentSystemEventListener and is a Renderer instance, "target" is the UIComponent instance that is to be rendered by this Renderer instance.

    If the class to which this annotation is attached implements ComponentSystemEventListener and is neither an instance of Renderer nor UIComponent, the action taken is unspecified. This case must not trigger any kind of error.

    If the class to which this annotation is attached implements SystemEventListener and does not implement ComponentSystemEventListener, "target" is the Application instance.

  • Determine the variant of subscribeToEvent()to call and the parameters to pass to it.

    If "target" is a UIComponent call UIComponent.subscribeToEvent(Class, ComponentSystemEventListener), passing the systemEventClass() of the annotation as the first argument and the instance of the class to which this annotation is attached (which must implement ComponentSystemEventListener) as the second argument.

    If "target" is the Application instance, inspect the value of the sourceClass() annotation attribute value.

    If the value is Void.class, call Application.subscribeToEvent(Class, SystemEventListener), passing the value of systemEventClass() as the first argument and the instance of the class to which this annotation is attached (which must implement SystemEventListener) as the second argument.

    Otherwise, call Application.subscribeToEvent(Class, Class, SystemEventListener), passing the value of systemEventClass() as the first argument, the value of sourceClass() as the second argument, and the instance of the class to which this annotation is attached (which must implement SystemEventListener) as the third argument.

Example: The standard renderer for jakarta.faces.resource.Stylesheet must have the following annotation declaration: 

 @ListenerFor(systemEventClass=PostAddToViewEvent.class)

This will cause the renderer to be added as a listener for the PostAddToViewEvent to all components that list it as their renderer.

Since:
2.0

  • Required Element Summary

    Required Elements 
    Modifier and Type Required Element Description
    Class<? extends SystemEvent> systemEventClass
    The kind of system event for which this class will be installed as a listener.

  • Optional Element Summary

    Optional Elements 
    Modifier and Type Optional Element Description
    Class sourceClass
    The kind of object that emits events of the type given by the value of the systemEventClass() attribute.

  • Element Details

    • systemEventClass

      Class<? extends SystemEvent> systemEventClass

      The kind of system event for which this class will be installed as a listener. The implementation only supports exact matches on the Class and must not honor subclass relationships. It is valid to have EL Expressions in the value of this attribute, as long as the expression resolves to an instance of the expected type.

      Returns:
      the event class

    • sourceClass

      Class sourceClass

      The kind of object that emits events of the type given by the value of the systemEventClass() attribute. It is valid to have Jakarta Expression Language Expressions in the value of this attribute, as long as the expression resolves to an instance of the expected type.

      Returns:
      the source class
      Default:
      java.lang.Void.class