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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.


New code should use the NotificationEmitter interface instead.


Implementations of this interface and of NotificationEmitter 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>
 *
 * <h3>Notification dispatch</h3>
 *
 * <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>New code should use the {@link NotificationEmitter} interface
 * instead.</p>
 *
 * <p>Implementations of this interface and of {@code NotificationEmitter}
 * 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 NotificationBroadcaster {

    
Adds a listener to this MBean.

Params:
  • listener – The listener object which will handle the
notifications emitted by the broadcaster.
  • filter – The filter object. If filter is null, no
filtering will be performed before handling notifications.
  • handback – An opaque object to be sent back to the
listener when a notification is emitted. This object cannot be
used by the Notification broadcaster object. It should be
resent unchanged with the notification to the listener.
Throws:
See Also:
/**
     * Adds a listener to this MBean.
     *
     * @param listener The listener object which will handle the
     * notifications emitted by the broadcaster.
     * @param filter The filter object. If filter is null, no
     * filtering will be performed before handling notifications.
     * @param handback An opaque object to be sent back to the
     * listener when a notification is emitted. This object cannot be
     * used by the Notification broadcaster object. It should be
     * resent unchanged with the notification to the listener.
     *
     * @exception IllegalArgumentException Listener parameter is null.
     *
     * @see #removeNotificationListener
     */
    public void addNotificationListener(NotificationListener listener,
                                        NotificationFilter filter,
                                        Object handback)
            throws java.lang.IllegalArgumentException;

    
Removes a listener from this MBean.  If the listener
has been registered with different handback objects or
notification filters, all entries corresponding to the listener
will be removed.

Params:
  • listener – A listener that was previously added to this
MBean.
Throws:
See Also:
/**
     * Removes a listener from this MBean.  If the listener
     * has been registered with different handback objects or
     * notification filters, all entries corresponding to the listener
     * will be removed.
     *
     * @param listener A listener that was previously added to this
     * MBean.
     *
     * @exception ListenerNotFoundException The listener is not
     * registered with the MBean.
     *
     * @see #addNotificationListener
     * @see NotificationEmitter#removeNotificationListener
     */
    public void removeNotificationListener(NotificationListener listener)
            throws ListenerNotFoundException;

    
Returns an array indicating, for each notification this
MBean may send, the name of the Java class of the notification
and the notification type.


It is not illegal for the MBean to send notifications not
described in this array.  However, some clients of the MBean
server may depend on the array being complete for their correct
functioning.


Returns:the array of possible notifications.
/**
     * <p>Returns an array indicating, for each notification this
     * MBean may send, the name of the Java class of the notification
     * and the notification type.</p>
     *
     * <p>It is not illegal for the MBean to send notifications not
     * described in this array.  However, some clients of the MBean
     * server may depend on the array being complete for their correct
     * functioning.</p>
     *
     * @return the array of possible notifications.
     */
    public MBeanNotificationInfo[] getNotificationInfo();
}