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package javax.management;

import java.util.Collections;
import java.util.List;
import java.util.Objects;
import java.util.concurrent.CopyOnWriteArrayList;
import java.util.concurrent.Executor;

import com.sun.jmx.remote.util.ClassLogger;


Provides an implementation of NotificationEmitter interface. This can be used as the super class of an MBean that sends notifications.


By default, the notification dispatch model is synchronous.
That is, when a thread calls sendNotification, the
NotificationListener.handleNotification method of each listener
is called within that thread. You can override this default
by overriding handleNotification in a subclass, or by passing an
Executor to the constructor.


If the method call of a filter or listener throws an Exception, then that exception does not prevent other listeners from being invoked. However, if the method call of a filter or of Executor.execute or of handleNotification (when no Excecutor is specified) throws an Error, then that Error is propagated to the caller of sendNotification.


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.


Since:1.5
/**
 * <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 NotificationBroadcasterSupport#NotificationBroadcasterSupport(Executor,
     * MBeanNotificationInfo[] info) NotificationBroadcasterSupport(null, null). 
/**
     * 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 Executor. When 
sendNotification is called, a listener is selected if it was added with a null NotificationFilter, or if 
isNotificationEnabled returns true for the notification being sent. The call to NotificationFilter.isNotificationEnabled takes place in the thread
that called sendNotification. Then, for each selected listener, executor.execute is called with a command that calls the handleNotification method. This constructor is equivalent to NotificationBroadcasterSupport#NotificationBroadcasterSupport(Executor,
     * MBeanNotificationInfo[] info) NotificationBroadcasterSupport(executor, null). 
Params:
  • executor – an executor used by the method sendNotification to
send each notification. If it is null, the thread calling sendNotification
will invoke the handleNotification method itself.
Since:1.6
/**
     * 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);
    }

    
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 NotificationBroadcasterSupport(null, info).


If the info array is not empty, then it is cloned by the constructor as if by info.clone(), and each call to getNotificationInfo() returns a new clone.


Params:
  • 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
/**
     * <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);
    }

    
Constructs a NotificationBroadcasterSupport with information about the notifications that may be sent, and where each listener is invoked using the given Executor.


When sendNotification is called, a listener is selected if it was added with a null NotificationFilter, or if isNotificationEnabled returns true for the notification being sent. The call to NotificationFilter.isNotificationEnabled takes
place in the thread that called
sendNotification. Then, for each selected listener, executor.execute is called with a command that calls the handleNotification
method.


If the info array is not empty, then it is cloned by the constructor as if by info.clone(), and each call to getNotificationInfo() returns a new clone.


Params:
  • executor – an executor used by the method
sendNotification to send each notification. If it
is null, the thread calling sendNotification will
invoke the handleNotification method itself.
  • 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
/**
     * <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.

Params:
  • listener – The listener to receive notifications.
  • filter – The filter object. If filter is null, no
filtering will be performed before handling notifications.
  • 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.
Throws:
See Also:
/**
     * 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 Executor was specified in the constructor, it will be given one task per selected listener to deliver the notification to that listener. 
Params:
  • notification – The notification to send.
/**
     * 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));
            }
        }
    }

    
This method is called by 
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.


The default implementation of this method is equivalent to

listener.handleNotification(notif, handback);



Params:
  • listener – the listener to which the notification is being
delivered.
  • notif – the notification being delivered to the listener.
  • handback – the handback object that was supplied when the
listener was added.
/**
     * <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.
     *
     */
    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;
        }

        @Override
        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);
        }

        @Override
        public int hashCode() {
            return Objects.hashCode(listener);
        }
    }

    private static class WildcardListenerInfo extends ListenerInfo {
        WildcardListenerInfo(NotificationListener listener) {
            super(listener, null, null);
        }

        @Override
        public boolean equals(Object o) {
            assert (!(o instanceof WildcardListenerInfo));
            return o.equals(this);
        }

        @Override
        public int hashCode() {
            return super.hashCode();
        }
    }

    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");
}