Interface NotificationEmitter

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.