J. Duke | 319a3b9 | 2007-12-01 00:00:00 +0000 | [diff] [blame^] | 1 | /* |
| 2 | * Copyright 2003-2005 Sun Microsystems, Inc. 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. Sun designates this |
| 8 | * particular file as subject to the "Classpath" exception as provided |
| 9 | * by Sun 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara, |
| 22 | * CA 95054 USA or visit www.sun.com if you need additional information or |
| 23 | * have any questions. |
| 24 | */ |
| 25 | |
| 26 | package sun.management; |
| 27 | |
| 28 | import javax.management.ListenerNotFoundException; |
| 29 | import javax.management.MBeanNotificationInfo; |
| 30 | import javax.management.Notification; |
| 31 | import javax.management.NotificationEmitter; |
| 32 | import javax.management.NotificationFilter; |
| 33 | import javax.management.NotificationListener; |
| 34 | |
| 35 | import java.util.List; |
| 36 | import java.util.ArrayList; |
| 37 | import java.util.ListIterator; |
| 38 | import java.util.Collections; |
| 39 | |
| 40 | /** |
| 41 | * Abstract helper class for notification emitter support. |
| 42 | */ |
| 43 | abstract class NotificationEmitterSupport implements NotificationEmitter { |
| 44 | |
| 45 | protected NotificationEmitterSupport() { |
| 46 | } |
| 47 | |
| 48 | private Object listenerLock = new Object(); |
| 49 | |
| 50 | // Implementation of NotificationEmitter interface |
| 51 | // Cloned from JMX NotificationBroadcasterSupport class. |
| 52 | public void addNotificationListener(NotificationListener listener, |
| 53 | NotificationFilter filter, |
| 54 | Object handback) { |
| 55 | |
| 56 | if (listener == null) { |
| 57 | throw new IllegalArgumentException ("Listener can't be null") ; |
| 58 | } |
| 59 | |
| 60 | /* Adding a new listener takes O(n) time where n is the number |
| 61 | of existing listeners. If you have a very large number of |
| 62 | listeners performance could degrade. That's a fairly |
| 63 | surprising configuration, and it is hard to avoid this |
| 64 | behaviour while still retaining the property that the |
| 65 | listenerList is not synchronized while notifications are |
| 66 | being sent through it. If this becomes a problem, a |
| 67 | possible solution would be a multiple-readers single-writer |
| 68 | setup, so any number of sendNotification() calls could run |
| 69 | concurrently but they would exclude an |
| 70 | add/removeNotificationListener. A simpler but less |
| 71 | efficient solution would be to clone the listener list |
| 72 | every time a notification is sent. */ |
| 73 | synchronized (listenerLock) { |
| 74 | List<ListenerInfo> newList = new ArrayList<ListenerInfo>(listenerList.size() + 1); |
| 75 | newList.addAll(listenerList); |
| 76 | newList.add(new ListenerInfo(listener, filter, handback)); |
| 77 | listenerList = newList; |
| 78 | } |
| 79 | } |
| 80 | |
| 81 | public void removeNotificationListener(NotificationListener listener) |
| 82 | throws ListenerNotFoundException { |
| 83 | |
| 84 | synchronized (listenerLock) { |
| 85 | List<ListenerInfo> newList = new ArrayList<ListenerInfo>(listenerList); |
| 86 | /* We scan the list of listeners in reverse order because |
| 87 | in forward order we would have to repeat the loop with |
| 88 | the same index after a remove. */ |
| 89 | for (int i=newList.size()-1; i>=0; i--) { |
| 90 | ListenerInfo li = (ListenerInfo)newList.get(i); |
| 91 | |
| 92 | if (li.listener == listener) |
| 93 | newList.remove(i); |
| 94 | } |
| 95 | if (newList.size() == listenerList.size()) |
| 96 | throw new ListenerNotFoundException("Listener not registered"); |
| 97 | listenerList = newList; |
| 98 | } |
| 99 | } |
| 100 | |
| 101 | public void removeNotificationListener(NotificationListener listener, |
| 102 | NotificationFilter filter, |
| 103 | Object handback) |
| 104 | throws ListenerNotFoundException { |
| 105 | |
| 106 | boolean found = false; |
| 107 | |
| 108 | synchronized (listenerLock) { |
| 109 | List<ListenerInfo> newList = new ArrayList<ListenerInfo>(listenerList); |
| 110 | final int size = newList.size(); |
| 111 | for (int i = 0; i < size; i++) { |
| 112 | ListenerInfo li = (ListenerInfo) newList.get(i); |
| 113 | |
| 114 | if (li.listener == listener) { |
| 115 | found = true; |
| 116 | if (li.filter == filter |
| 117 | && li.handback == handback) { |
| 118 | newList.remove(i); |
| 119 | listenerList = newList; |
| 120 | return; |
| 121 | } |
| 122 | } |
| 123 | } |
| 124 | } |
| 125 | |
| 126 | if (found) { |
| 127 | /* We found this listener, but not with the given filter |
| 128 | * and handback. A more informative exception message may |
| 129 | * make debugging easier. */ |
| 130 | throw new ListenerNotFoundException("Listener not registered " + |
| 131 | "with this filter and " + |
| 132 | "handback"); |
| 133 | } else { |
| 134 | throw new ListenerNotFoundException("Listener not registered"); |
| 135 | } |
| 136 | } |
| 137 | |
| 138 | void sendNotification(Notification notification) { |
| 139 | |
| 140 | if (notification == null) { |
| 141 | return; |
| 142 | } |
| 143 | |
| 144 | List<ListenerInfo> currentList; |
| 145 | synchronized (listenerLock) { |
| 146 | currentList = listenerList; |
| 147 | } |
| 148 | |
| 149 | final int size = currentList.size(); |
| 150 | for (int i = 0; i < size; i++) { |
| 151 | ListenerInfo li = (ListenerInfo) currentList.get(i); |
| 152 | |
| 153 | if (li.filter == null |
| 154 | || li.filter.isNotificationEnabled(notification)) { |
| 155 | try { |
| 156 | li.listener.handleNotification(notification, li.handback); |
| 157 | } catch (Exception e) { |
| 158 | e.printStackTrace(); |
| 159 | throw new InternalError("Error in invoking listener"); |
| 160 | } |
| 161 | } |
| 162 | } |
| 163 | } |
| 164 | |
| 165 | boolean hasListeners() { |
| 166 | synchronized (listenerLock) { |
| 167 | return !listenerList.isEmpty(); |
| 168 | } |
| 169 | } |
| 170 | |
| 171 | private class ListenerInfo { |
| 172 | public NotificationListener listener; |
| 173 | NotificationFilter filter; |
| 174 | Object handback; |
| 175 | |
| 176 | public ListenerInfo(NotificationListener listener, |
| 177 | NotificationFilter filter, |
| 178 | Object handback) { |
| 179 | this.listener = listener; |
| 180 | this.filter = filter; |
| 181 | this.handback = handback; |
| 182 | } |
| 183 | } |
| 184 | |
| 185 | /** |
| 186 | * Current list of listeners, a List of ListenerInfo. The object |
| 187 | * referenced by this field is never modified. Instead, the field |
| 188 | * is set to a new object when a listener is added or removed, |
| 189 | * within a synchronized(this). In this way, there is no need to |
| 190 | * synchronize when traversing the list to send a notification to |
| 191 | * the listeners in it. That avoids potential deadlocks if the |
| 192 | * listeners end up depending on other threads that are themselves |
| 193 | * accessing this NotificationBroadcasterSupport. |
| 194 | */ |
| 195 | private List<ListenerInfo> listenerList = Collections.emptyList(); |
| 196 | |
| 197 | abstract public MBeanNotificationInfo[] getNotificationInfo(); |
| 198 | } |