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1   /*
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3    * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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5    * This code is free software; you can redistribute it and/or modify it
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7    * published by the Free Software Foundation.  Oracle designates this
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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
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19   * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20   *
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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  }