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package javax.faces.event;
import java.lang.annotation.ElementType;
import java.lang.annotation.Repeatable;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
import java.lang.annotation.Inherited;
/**
* <p class="changed_added_2_0">Classes tagged with this annotation are
* installed as listeners using the method {@link
* javax.faces.application.Application#subscribeToEvent} or {@link
* javax.faces.component.UIComponent#subscribeToEvent} (depending on the
* circumstances, described below).</p>
*
* <div class="changed_added_2_0">
*
* <p>The default implementation must support attaching this annotation
* to {@link javax.faces.component.UIComponent} or {@link
* javax.faces.render.Renderer} classes. In both cases, the annotation
* processing described herein must commence during the implementation
* of any variant of {@link
* javax.faces.application.Application}<code>.createComponent()</code>
* and must complete before the <code>UIComponent</code> instance is
* returned from <code>createComponent()</code>. The annotation
* processing must proceed according to an algorithm semantically
* equivalent to the following.</p>
* <ul>
<li><p> If this annotation is not present on the class in
question, no action must be taken. </p>
<p>Determine the "target" on which to call
<code>subscribeToEvent</code>.</p>
<p>If the class to which this annotation is attached
implements {@link ComponentSystemEventListener} and is a
<code>UIComponent</code> instance, "target" is the
<code>UIComponent</code> instance.</p>
<p>If the class to which this annotation is attached
implements {@link ComponentSystemEventListener} and is a
<code>Renderer</code> instance, "target" is the
<code>UIComponent</code> instance that is to be rendered by
this <code>Renderer</code> instance.</p>
<p>If the class to which this annotation is attached
implements {@link ComponentSystemEventListener} and is neither
an instance of <code>Renderer</code> nor
<code>UIComponent</code>, the action taken is
unspecified. This case must not trigger any kind of error.</p>
<p>If the class to which this annotation is attached
implements <code>SystemEventListener</code> and does not
implement <code>ComponentSystemEventListener</code>, "target"
is the {@link javax.faces.application.Application}
instance.</p>
</li>
<li>
<p>Determine the variant of <code>subscribeToEvent()</code>to
call and the parameters to pass to it.</p>
<p>If "target" is a <code>UIComponent</code> call {@link
javax.faces.component.UIComponent#subscribeToEvent(Class,
ComponentSystemEventListener)}, passing the {@link
#systemEventClass} of the annotation as the first argument and
the instance of the class to which this annotation is attached
(which must implement
<code>ComponentSystemEventListener</code>) as the second
argument.</p>
<p>If "target" is the {@link
javax.faces.application.Application} instance, inspect the
value of the {@link #sourceClass} annotation attribute value.</p>
<p>If the value is <code>Void.class</code>, call {@link
javax.faces.application.Application#subscribeToEvent(Class,
SystemEventListener)}, passing the value of {@link
#systemEventClass} as the first argument and the instance of the
class to which this annotation is attached (which must
implement <code>SystemEventListener) as the second
argument.</code></p>
<p>Otherwise, call {@link
javax.faces.application.Application#subscribeToEvent(Class,
Class, SystemEventListener)}, passing the value of {@link
#systemEventClass} as the first argument, the value of {@link
#sourceClass} as the second argument, and the instance of the
class to which this annotation is attached (which must
implement <code>SystemEventListener) as the third
argument.</code></p>
</li>
* </ul>
* <p>Example: The standard renderer for
* <code>javax.faces.resource.Stylesheet</code> must have the following
* annotation declaration:</p>
* <pre><code>@ListenerFor(systemEventClass=PostAddToViewEvent.class)</code></pre>
* <p>This will cause the renderer to be added as a listener for the
* {@link PostAddToViewEvent} to all components that list it as their
* renderer.</p>
* </div>
*
* @since 2.0
*/
@Retention(value=RetentionPolicy.RUNTIME)
@Target(value=ElementType.TYPE)
@Inherited
@Repeatable(ListenersFor.class)
public @interface ListenerFor {
/**
* <p class="changed_added_2_0">The kind of system event for which
* this class will be installed as a listener. The implementation
* only supports exact matches on the <code>Class</code> 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.</p>
*
* @return the event class
*/
public Class<? extends SystemEvent> systemEventClass();
/**
* <p class="changed_added_2_0">The kind of object that emits events
* of the type given by the value of the {@link #systemEventClass}
* attribute. 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.</p>
*
* @return the source class
*/
public Class sourceClass() default Void.class;
}