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package javax.management;

import java.util.concurrent.CopyOnWriteArrayList;  // for Javadoc


Interface implemented by an MBean that emits Notifications. It
allows a listener to be registered with the MBean as a notification
listener.


Notification dispatch


When an MBean emits a notification, it considers each listener that has been added with addNotificationListener and not subsequently removed with removeNotificationListener. If a filter was provided with that listener, and if the filter's isNotificationEnabled method returns false, the listener is ignored. Otherwise, the listener's handleNotification method is called with the notification, as well as the handback object that was provided to addNotificationListener.


If the same listener is added more than once, it is considered as many times as it was
added.  It is often useful to add the same listener with different filters or handback
objects.


Implementations of this interface can differ regarding the thread in which the methods
of filters and listeners are called.


If the method call of a filter or listener throws an Exception, then that exception should not prevent other listeners from being invoked. However, if the method call throws an Error, then it is recommended that processing of the notification stop at that point, and if it is possible to propagate the Error to the sender of the notification, this should be done.


This interface should be used by new code in preference to the NotificationBroadcaster interface.


Implementations of this interface and of NotificationBroadcaster should be careful about synchronization. In particular, it is not a good idea for an implementation to hold any locks while it is calling a listener. To deal with the possibility that the list of listeners might change while a notification is being dispatched, a good strategy is to use a CopyOnWriteArrayList for this list. 
Since:1.5
/**
 * <p>Interface implemented by an MBean that emits Notifications. It
 * allows a listener to be registered with the MBean as a notification
 * listener.</p>
 *
 * <h2>Notification dispatch</h2>
 *
 *<p>When an MBean emits a notification, it considers each listener that has been
 * added with {@link #addNotificationListener addNotificationListener} and not
 * subsequently removed with {@link #removeNotificationListener removeNotificationListener}.
 * If a filter was provided with that listener, and if the filter's
 * {@link NotificationFilter#isNotificationEnabled isNotificationEnabled} method returns
 * false, the listener is ignored.  Otherwise, the listener's
 * {@link NotificationListener#handleNotification handleNotification} method is called with
 * the notification, as well as the handback object that was provided to
 * {@code addNotificationListener}.</p>
 *
 * <p>If the same listener is added more than once, it is considered as many times as it was
 * added.  It is often useful to add the same listener with different filters or handback
 * objects.</p>
 *
 * <p>Implementations of this interface can differ regarding the thread in which the methods
 * of filters and listeners are called.</p>
 *
 * <p>If the method call of a filter or listener throws an {@link Exception}, then that
 * exception should not prevent other listeners from being invoked.  However, if the method
 * call throws an {@link Error}, then it is recommended that processing of the notification
 * stop at that point, and if it is possible to propagate the {@code Error} to the sender of
 * the notification, this should be done.</p>
 *
 * <p>This interface should be used by new code in preference to the
 * {@link NotificationBroadcaster} interface.</p>
 *
 * <p>Implementations of this interface and of {@code NotificationBroadcaster}
 * should be careful about synchronization.  In particular, it is not a good
 * idea for an implementation to hold any locks while it is calling a
 * listener.  To deal with the possibility that the list of listeners might
 * change while a notification is being dispatched, a good strategy is to
 * use a {@link CopyOnWriteArrayList} for this list.
 *
 * @since 1.5
 */
public interface NotificationEmitter extends NotificationBroadcaster {
    
Removes a listener from this MBean.  The MBean must have a
listener that exactly matches the given listener,
filter, and handback parameters.  If
there is more than one such listener, only one is removed.


The filter and handback parameters
may be null if and only if they are null in a listener to be
removed.


Params:
  • listener – A listener that was previously added to this
MBean.
  • filter – The filter that was specified when the listener
was added.
  • handback – The handback that was specified when the listener was
added.
Throws:
  • ListenerNotFoundException – The listener is not
registered with the MBean, or it is not registered with the
given filter and handback.
/**
     * <p>Removes a listener from this MBean.  The MBean must have a
     * listener that exactly matches the given <code>listener</code>,
     * <code>filter</code>, and <code>handback</code> parameters.  If
     * there is more than one such listener, only one is removed.</p>
     *
     * <p>The <code>filter</code> and <code>handback</code> parameters
     * may be null if and only if they are null in a listener to be
     * removed.</p>
     *
     * @param listener A listener that was previously added to this
     * MBean.
     * @param filter The filter that was specified when the listener
     * was added.
     * @param handback The handback that was specified when the listener was
     * added.
     *
     * @exception ListenerNotFoundException The listener is not
     * registered with the MBean, or it is not registered with the
     * given filter and handback.
     */
    public void removeNotificationListener(NotificationListener listener,
                                           NotificationFilter filter,
                                           Object handback)
            throws ListenerNotFoundException;
}