/*
* @(#)NotificationBroadcasterSupport.java 1.65 05/11/17
*
* Copyright 2006 Sun Microsystems, Inc. All rights reserved.
* SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
*/
package javax.management;
import java.util.Collections;
import java.util.List;
import java.util.concurrent.CopyOnWriteArrayList;
import java.util.concurrent.Executor;
import com.sun.jmx.remote.util.ClassLogger;
/**
* <p>Provides an implementation of {@link
* javax.management.NotificationEmitter NotificationEmitter}
* interface. This can be used as the super class of an MBean that
* sends notifications.</p>
*
* <p>By default, the notification dispatch model is synchronous.
* That is, when a thread calls sendNotification, the
* <code>NotificationListener.handleNotification</code> method of each listener
* is called within that thread. You can override this default
* by overriding <code>handleNotification</code> in a subclass, or by passing an
* Executor to the constructor.</p>
*
* <p>If the method call of a filter or listener throws an {@link Exception},
* then that exception does not prevent other listeners from being invoked. However,
* if the method call of a filter or of {@code Executor.execute} or of
* {@code handleNotification} (when no {@code Excecutor} is specified) throws an
* {@link Error}, then that {@code Error} is propagated to the caller of
* {@link #sendNotification sendNotification}.</p>
*
* <p>Remote listeners added using the JMX Remote API (see JMXConnector) are not
* usually called synchronously. That is, when sendNotification returns, it is
* not guaranteed that any remote listeners have yet received the notification.</p>
*
* @since 1.5
*/
public class NotificationBroadcasterSupport implements NotificationEmitter {
/**
* Constructs a NotificationBroadcasterSupport where each listener is invoked by the
* thread sending the notification. This constructor is equivalent to
* {@link NotificationBroadcasterSupport#NotificationBroadcasterSupport(Executor,
* MBeanNotificationInfo[] info) NotificationBroadcasterSupport(null, null)}.
*/
public NotificationBroadcasterSupport() {
this(null, (MBeanNotificationInfo[]) null);
}
/**
* Constructs a NotificationBroadcasterSupport where each listener is invoked using
* the given {@link java.util.concurrent.Executor}. When {@link #sendNotification
* sendNotification} is called, a listener is selected if it was added with a null
* {@link NotificationFilter}, or if {@link NotificationFilter#isNotificationEnabled
* isNotificationEnabled} returns true for the notification being sent. The call to
* <code>NotificationFilter.isNotificationEnabled</code> takes place in the thread
* that called <code>sendNotification</code>. Then, for each selected listener,
* {@link Executor#execute executor.execute} is called with a command
* that calls the <code>handleNotification</code> method.
* This constructor is equivalent to
* {@link NotificationBroadcasterSupport#NotificationBroadcasterSupport(Executor,
* MBeanNotificationInfo[] info) NotificationBroadcasterSupport(executor, null)}.
* @param executor an executor used by the method <code>sendNotification</code> to
* send each notification. If it is null, the thread calling <code>sendNotification</code>
* will invoke the <code>handleNotification</code> method itself.
* @since 1.6
*/
public NotificationBroadcasterSupport(Executor executor) {
this(executor, (MBeanNotificationInfo[]) null);
}
/**
* <p>Constructs a NotificationBroadcasterSupport with information
* about the notifications that may be sent. Each listener is
* invoked by the thread sending the notification. This
* constructor is equivalent to {@link
* NotificationBroadcasterSupport#NotificationBroadcasterSupport(Executor,
* MBeanNotificationInfo[] info)
* NotificationBroadcasterSupport(null, info)}.</p>
*
* <p>If the <code>info</code> array is not empty, then it is
* cloned by the constructor as if by {@code info.clone()}, and
* each call to {@link #getNotificationInfo()} returns a new
* clone.</p>
*
* @param info an array indicating, for each notification this
* MBean may send, the name of the Java class of the notification
* and the notification type. Can be null, which is equivalent to
* an empty array.
*
* @since 1.6
*/
public NotificationBroadcasterSupport(MBeanNotificationInfo... info) {
this(null, info);
}
/**
* <p>Constructs a NotificationBroadcasterSupport with information about the notifications that may be sent,
* and where each listener is invoked using the given {@link java.util.concurrent.Executor}.</p>
*
* <p>When {@link #sendNotification sendNotification} is called, a
* listener is selected if it was added with a null {@link
* NotificationFilter}, or if {@link
* NotificationFilter#isNotificationEnabled isNotificationEnabled}
* returns true for the notification being sent. The call to
* <code>NotificationFilter.isNotificationEnabled</code> takes
* place in the thread that called
* <code>sendNotification</code>. Then, for each selected
* listener, {@link Executor#execute executor.execute} is called
* with a command that calls the <code>handleNotification</code>
* method.</p>
*
* <p>If the <code>info</code> array is not empty, then it is
* cloned by the constructor as if by {@code info.clone()}, and
* each call to {@link #getNotificationInfo()} returns a new
* clone.</p>
*
* @param executor an executor used by the method
* <code>sendNotification</code> to send each notification. If it
* is null, the thread calling <code>sendNotification</code> will
* invoke the <code>handleNotification</code> method itself.
*
* @param info an array indicating, for each notification this
* MBean may send, the name of the Java class of the notification
* and the notification type. Can be null, which is equivalent to
* an empty array.
*
* @since 1.6
*/
public NotificationBroadcasterSupport(Executor executor,
MBeanNotificationInfo... info) {
this.executor = (executor != null) ? executor : defaultExecutor;
notifInfo = info == null ? NO_NOTIFICATION_INFO : info.clone();
}
/**
* Adds a listener.
*
* @param listener The listener to receive notifications.
* @param filter The filter object. If filter is null, no
* filtering will be performed before handling notifications.
* @param handback An opaque object to be sent back to the
* listener when a notification is emitted. This object cannot be
* used by the Notification broadcaster object. It should be
* resent unchanged with the notification to the listener.
*
* @exception IllegalArgumentException thrown if the listener is null.
*
* @see #removeNotificationListener
*/
public void addNotificationListener(NotificationListener listener,
NotificationFilter filter,
Object handback) {
if (listener == null) {
throw new IllegalArgumentException ("Listener can't be null") ;
}
listenerList.add(new ListenerInfo(listener, filter, handback));
}
public void removeNotificationListener(NotificationListener listener)
throws ListenerNotFoundException {
ListenerInfo wildcard = new WildcardListenerInfo(listener);
boolean removed =
listenerList.removeAll(Collections.singleton(wildcard));
if (!removed)
throw new ListenerNotFoundException("Listener not registered");
}
public void removeNotificationListener(NotificationListener listener,
NotificationFilter filter,
Object handback)
throws ListenerNotFoundException {
ListenerInfo li = new ListenerInfo(listener, filter, handback);
boolean removed = listenerList.remove(li);
if (!removed) {
throw new ListenerNotFoundException("Listener not registered " +
"(with this filter and " +
"handback)");
// or perhaps not registered at all
}
}
public MBeanNotificationInfo[] getNotificationInfo() {
if (notifInfo.length == 0)
return notifInfo;
else
return notifInfo.clone();
}
/**
* Sends a notification.
*
* If an {@code Executor} was specified in the constructor, it will be given one
* task per selected listener to deliver the notification to that listener.
*
* @param notification The notification to send.
*/
public void sendNotification(Notification notification) {
if (notification == null) {
return;
}
boolean enabled;
for (ListenerInfo li : listenerList) {
try {
enabled = li.filter == null ||
li.filter.isNotificationEnabled(notification);
} catch (Exception e) {
if (logger.debugOn()) {
logger.debug("sendNotification", e);
}
continue;
}
if (enabled) {
executor.execute(new SendNotifJob(notification, li));
}
}
}
/**
* <p>This method is called by {@link #sendNotification
* sendNotification} for each listener in order to send the
* notification to that listener. It can be overridden in
* subclasses to change the behavior of notification delivery,
* for instance to deliver the notification in a separate
* thread.</p>
*
* <p>The default implementation of this method is equivalent to
* <pre>
* listener.handleNotification(notif, handback);
* </pre>
*
* @param listener the listener to which the notification is being
* delivered.
* @param notif the notification being delivered to the listener.
* @param handback the handback object that was supplied when the
* listener was added.
*
* @since.unbundled JMX 1.2
*/
protected void handleNotification(NotificationListener listener,
Notification notif, Object handback) {
listener.handleNotification(notif, handback);
}
// private stuff
private static class ListenerInfo {
NotificationListener listener;
NotificationFilter filter;
Object handback;
ListenerInfo(NotificationListener listener,
NotificationFilter filter,
Object handback) {
this.listener = listener;
this.filter = filter;
this.handback = handback;
}
public boolean equals(Object o) {
if (!(o instanceof ListenerInfo))
return false;
ListenerInfo li = (ListenerInfo) o;
if (li instanceof WildcardListenerInfo)
return (li.listener == listener);
else
return (li.listener == listener && li.filter == filter
&& li.handback == handback);
}
}
private static class WildcardListenerInfo extends ListenerInfo {
WildcardListenerInfo(NotificationListener listener) {
super(listener, null, null);
}
public boolean equals(Object o) {
assert (!(o instanceof WildcardListenerInfo));
return o.equals(this);
}
}
private List<ListenerInfo> listenerList =
new CopyOnWriteArrayList<ListenerInfo>();
// since 1.6
private final Executor executor;
private final MBeanNotificationInfo[] notifInfo;
private final static Executor defaultExecutor = new Executor() {
// DirectExecutor using caller thread
public void execute(Runnable r) {
r.run();
}
};
private static final MBeanNotificationInfo[] NO_NOTIFICATION_INFO =
new MBeanNotificationInfo[0];
private class SendNotifJob implements Runnable {
public SendNotifJob(Notification notif, ListenerInfo listenerInfo) {
this.notif = notif;
this.listenerInfo = listenerInfo;
}
public void run() {
try {
handleNotification(listenerInfo.listener,
notif, listenerInfo.handback);
} catch (Exception e) {
if (logger.debugOn()) {
logger.debug("SendNotifJob-run", e);
}
}
}
private final Notification notif;
private final ListenerInfo listenerInfo;
}
private static final ClassLogger logger =
new ClassLogger("javax.management", "NotificationBroadcasterSupport");
}
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