1 /*
   2  * Copyright (c) 2002, 2007, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.  Oracle designates this
   8  * particular file as subject to the "Classpath" exception as provided
   9  * by Oracle in the LICENSE file that accompanied this code.
  10  *
  11  * This code is distributed in the hope that it will be useful, but WITHOUT
  12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  14  * version 2 for more details (a copy is included in the LICENSE file that
  15  * accompanied this code).
  16  *
  17  * You should have received a copy of the GNU General Public License version
  18  * 2 along with this work; if not, write to the Free Software Foundation,
  19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  20  *
  21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  22  * or visit www.oracle.com if you need additional information or have any
  23  * questions.
  24  */
  25 
  26 package javax.management;
  27 
  28 import java.util.concurrent.CopyOnWriteArrayList;  // for Javadoc
  29 
  30 /**
  31  * <p>Interface implemented by an MBean that emits Notifications. It
  32  * allows a listener to be registered with the MBean as a notification
  33  * listener.</p>
  34  *
  35  * <h3>Notification dispatch</h3>
  36  *
  37  *<p>When an MBean emits a notification, it considers each listener that has been
  38  * added with {@link #addNotificationListener addNotificationListener} and not
  39  * subsequently removed with {@link #removeNotificationListener removeNotificationListener}.
  40  * If a filter was provided with that listener, and if the filter's
  41  * {@link NotificationFilter#isNotificationEnabled isNotificationEnabled} method returns
  42  * false, the listener is ignored.  Otherwise, the listener's
  43  * {@link NotificationListener#handleNotification handleNotification} method is called with
  44  * the notification, as well as the handback object that was provided to
  45  * {@code addNotificationListener}.</p>
  46  *
  47  * <p>If the same listener is added more than once, it is considered as many times as it was
  48  * added.  It is often useful to add the same listener with different filters or handback
  49  * objects.</p>
  50  *
  51  * <p>Implementations of this interface can differ regarding the thread in which the methods
  52  * of filters and listeners are called.</p>
  53  *
  54  * <p>If the method call of a filter or listener throws an {@link Exception}, then that
  55  * exception should not prevent other listeners from being invoked.  However, if the method
  56  * call throws an {@link Error}, then it is recommended that processing of the notification
  57  * stop at that point, and if it is possible to propagate the {@code Error} to the sender of
  58  * the notification, this should be done.</p>
  59  *
  60  * <p>This interface should be used by new code in preference to the
  61  * {@link NotificationBroadcaster} interface.</p>
  62  *
  63  * <p>Implementations of this interface and of {@code NotificationBroadcaster}
  64  * should be careful about synchronization.  In particular, it is not a good
  65  * idea for an implementation to hold any locks while it is calling a
  66  * listener.  To deal with the possibility that the list of listeners might
  67  * change while a notification is being dispatched, a good strategy is to
  68  * use a {@link CopyOnWriteArrayList} for this list.
  69  *
  70  * @since 1.5
  71  */
  72 public interface NotificationEmitter extends NotificationBroadcaster {
  73     /**
  74      * <p>Removes a listener from this MBean.  The MBean must have a
  75      * listener that exactly matches the given <code>listener</code>,
  76      * <code>filter</code>, and <code>handback</code> parameters.  If
  77      * there is more than one such listener, only one is removed.</p>
  78      *
  79      * <p>The <code>filter</code> and <code>handback</code> parameters
  80      * may be null if and only if they are null in a listener to be
  81      * removed.</p>
  82      *
  83      * @param listener A listener that was previously added to this
  84      * MBean.
  85      * @param filter The filter that was specified when the listener
  86      * was added.
  87      * @param handback The handback that was specified when the listener was
  88      * added.
  89      *
  90      * @exception ListenerNotFoundException The listener is not
  91      * registered with the MBean, or it is not registered with the
  92      * given filter and handback.
  93      */
  94     public void removeNotificationListener(NotificationListener listener,
  95                                            NotificationFilter filter,
  96                                            Object handback)
  97             throws ListenerNotFoundException;
  98 }