author | sjiang |
Fri, 17 Apr 2015 09:40:02 +0200 | |
changeset 30355 | e37c7eba132f |
parent 25859 | 3317bb8137f4 |
permissions | -rw-r--r-- |
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/* |
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* Copyright (c) 2003, 2015, Oracle and/or its affiliates. All rights reserved. |
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
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* |
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* This code is free software; you can redistribute it and/or modify it |
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* under the terms of the GNU General Public License version 2 only, as |
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* published by the Free Software Foundation. Oracle designates this |
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* particular file as subject to the "Classpath" exception as provided |
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* by Oracle in the LICENSE file that accompanied this code. |
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* |
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* This code is distributed in the hope that it will be useful, but WITHOUT |
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
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* version 2 for more details (a copy is included in the LICENSE file that |
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* accompanied this code). |
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* |
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* You should have received a copy of the GNU General Public License version |
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* 2 along with this work; if not, write to the Free Software Foundation, |
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
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* |
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
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* or visit www.oracle.com if you need additional information or have any |
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* questions. |
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*/ |
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package sun.management; |
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import javax.management.ListenerNotFoundException; |
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import javax.management.MBeanNotificationInfo; |
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import javax.management.Notification; |
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import javax.management.NotificationEmitter; |
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import javax.management.NotificationFilter; |
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import javax.management.NotificationListener; |
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import java.util.List; |
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import java.util.ArrayList; |
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import java.util.Collections; |
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/** |
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* Abstract helper class for notification emitter support. |
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*/ |
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public abstract class NotificationEmitterSupport implements NotificationEmitter { |
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protected NotificationEmitterSupport() { |
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} |
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private Object listenerLock = new Object(); |
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// Implementation of NotificationEmitter interface |
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// Cloned from JMX NotificationBroadcasterSupport class. |
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public void addNotificationListener(NotificationListener listener, |
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NotificationFilter filter, |
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Object handback) { |
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if (listener == null) { |
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throw new IllegalArgumentException ("Listener can't be null") ; |
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} |
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/* Adding a new listener takes O(n) time where n is the number |
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of existing listeners. If you have a very large number of |
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listeners performance could degrade. That's a fairly |
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surprising configuration, and it is hard to avoid this |
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behaviour while still retaining the property that the |
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listenerList is not synchronized while notifications are |
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being sent through it. If this becomes a problem, a |
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possible solution would be a multiple-readers single-writer |
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setup, so any number of sendNotification() calls could run |
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concurrently but they would exclude an |
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add/removeNotificationListener. A simpler but less |
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efficient solution would be to clone the listener list |
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every time a notification is sent. */ |
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synchronized (listenerLock) { |
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List<ListenerInfo> newList = new ArrayList<>(listenerList.size() + 1); |
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newList.addAll(listenerList); |
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newList.add(new ListenerInfo(listener, filter, handback)); |
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listenerList = newList; |
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} |
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} |
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public void removeNotificationListener(NotificationListener listener) |
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throws ListenerNotFoundException { |
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synchronized (listenerLock) { |
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List<ListenerInfo> newList = new ArrayList<>(listenerList); |
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/* We scan the list of listeners in reverse order because |
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in forward order we would have to repeat the loop with |
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the same index after a remove. */ |
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for (int i=newList.size()-1; i>=0; i--) { |
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ListenerInfo li = newList.get(i); |
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if (li.listener == listener) |
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newList.remove(i); |
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} |
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if (newList.size() == listenerList.size()) |
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throw new ListenerNotFoundException("Listener not registered"); |
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listenerList = newList; |
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} |
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} |
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public void removeNotificationListener(NotificationListener listener, |
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NotificationFilter filter, |
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Object handback) |
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throws ListenerNotFoundException { |
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boolean found = false; |
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synchronized (listenerLock) { |
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List<ListenerInfo> newList = new ArrayList<>(listenerList); |
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final int size = newList.size(); |
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for (int i = 0; i < size; i++) { |
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ListenerInfo li = newList.get(i); |
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if (li.listener == listener) { |
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found = true; |
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if (li.filter == filter |
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&& li.handback == handback) { |
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newList.remove(i); |
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listenerList = newList; |
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return; |
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} |
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} |
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} |
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} |
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if (found) { |
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/* We found this listener, but not with the given filter |
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* and handback. A more informative exception message may |
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* make debugging easier. */ |
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throw new ListenerNotFoundException("Listener not registered " + |
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"with this filter and " + |
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"handback"); |
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} else { |
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throw new ListenerNotFoundException("Listener not registered"); |
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} |
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} |
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public void sendNotification(Notification notification) { |
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if (notification == null) { |
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return; |
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} |
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List<ListenerInfo> currentList; |
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synchronized (listenerLock) { |
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currentList = listenerList; |
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} |
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final int size = currentList.size(); |
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for (int i = 0; i < size; i++) { |
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ListenerInfo li = currentList.get(i); |
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if (li.filter == null |
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|| li.filter.isNotificationEnabled(notification)) { |
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try { |
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li.listener.handleNotification(notification, li.handback); |
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} catch (Exception e) { |
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e.printStackTrace(); |
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throw new AssertionError("Error in invoking listener"); |
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} |
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} |
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} |
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} |
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public boolean hasListeners() { |
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synchronized (listenerLock) { |
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return !listenerList.isEmpty(); |
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} |
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} |
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private class ListenerInfo { |
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public NotificationListener listener; |
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NotificationFilter filter; |
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Object handback; |
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public ListenerInfo(NotificationListener listener, |
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NotificationFilter filter, |
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Object handback) { |
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this.listener = listener; |
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this.filter = filter; |
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this.handback = handback; |
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} |
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} |
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/** |
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* Current list of listeners, a List of ListenerInfo. The object |
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* referenced by this field is never modified. Instead, the field |
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* is set to a new object when a listener is added or removed, |
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* within a synchronized(this). In this way, there is no need to |
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* synchronize when traversing the list to send a notification to |
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* the listeners in it. That avoids potential deadlocks if the |
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* listeners end up depending on other threads that are themselves |
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* accessing this NotificationBroadcasterSupport. |
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*/ |
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private List<ListenerInfo> listenerList = Collections.emptyList(); |
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abstract public MBeanNotificationInfo[] getNotificationInfo(); |
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} |