1/*
2 * Copyright (c) 1999, 2005, 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
27package javax.management;
28
29import java.util.concurrent.CopyOnWriteArrayList;  // for Javadoc
30
31/**
32 * <p>Interface implemented by an MBean that emits Notifications. It
33 * allows a listener to be registered with the MBean as a notification
34 * listener.</p>
35 *
36 * <h3>Notification dispatch</h3>
37 *
38 * <p>When an MBean emits a notification, it considers each listener that has been
39 * added with {@link #addNotificationListener addNotificationListener} and not
40 * subsequently removed with {@link #removeNotificationListener removeNotificationListener}.
41 * If a filter was provided with that listener, and if the filter's
42 * {@link NotificationFilter#isNotificationEnabled isNotificationEnabled} method returns
43 * false, the listener is ignored.  Otherwise, the listener's
44 * {@link NotificationListener#handleNotification handleNotification} method is called with
45 * the notification, as well as the handback object that was provided to
46 * {@code addNotificationListener}.</p>
47 *
48 * <p>If the same listener is added more than once, it is considered as many times as it was
49 * added.  It is often useful to add the same listener with different filters or handback
50 * objects.</p>
51 *
52 * <p>Implementations of this interface can differ regarding the thread in which the methods
53 * of filters and listeners are called.</p>
54 *
55 * <p>If the method call of a filter or listener throws an {@link Exception}, then that
56 * exception should not prevent other listeners from being invoked.  However, if the method
57 * call throws an {@link Error}, then it is recommended that processing of the notification
58 * stop at that point, and if it is possible to propagate the {@code Error} to the sender of
59 * the notification, this should be done.</p>
60 *
61 * <p>New code should use the {@link NotificationEmitter} interface
62 * instead.</p>
63 *
64 * <p>Implementations of this interface and of {@code NotificationEmitter}
65 * should be careful about synchronization.  In particular, it is not a good
66 * idea for an implementation to hold any locks while it is calling a
67 * listener.  To deal with the possibility that the list of listeners might
68 * change while a notification is being dispatched, a good strategy is to
69 * use a {@link CopyOnWriteArrayList} for this list.
70 *
71 * @since 1.5
72 */
73public interface NotificationBroadcaster {
74
75    /**
76     * Adds a listener to this MBean.
77     *
78     * @param listener The listener object which will handle the
79     * notifications emitted by the broadcaster.
80     * @param filter The filter object. If filter is null, no
81     * filtering will be performed before handling notifications.
82     * @param handback An opaque object to be sent back to the
83     * listener when a notification is emitted. This object cannot be
84     * used by the Notification broadcaster object. It should be
85     * resent unchanged with the notification to the listener.
86     *
87     * @exception IllegalArgumentException Listener parameter is null.
88     *
89     * @see #removeNotificationListener
90     */
91    public void addNotificationListener(NotificationListener listener,
92                                        NotificationFilter filter,
93                                        Object handback)
94            throws java.lang.IllegalArgumentException;
95
96    /**
97     * Removes a listener from this MBean.  If the listener
98     * has been registered with different handback objects or
99     * notification filters, all entries corresponding to the listener
100     * will be removed.
101     *
102     * @param listener A listener that was previously added to this
103     * MBean.
104     *
105     * @exception ListenerNotFoundException The listener is not
106     * registered with the MBean.
107     *
108     * @see #addNotificationListener
109     * @see NotificationEmitter#removeNotificationListener
110     */
111    public void removeNotificationListener(NotificationListener listener)
112            throws ListenerNotFoundException;
113
114    /**
115     * <p>Returns an array indicating, for each notification this
116     * MBean may send, the name of the Java class of the notification
117     * and the notification type.</p>
118     *
119     * <p>It is not illegal for the MBean to send notifications not
120     * described in this array.  However, some clients of the MBean
121     * server may depend on the array being complete for their correct
122     * functioning.</p>
123     *
124     * @return the array of possible notifications.
125     */
126    public MBeanNotificationInfo[] getNotificationInfo();
127}
128