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Diffstat (limited to 'libjava/classpath/javax/management/NotificationBroadcasterSupport.java')
| -rw-r--r-- | libjava/classpath/javax/management/NotificationBroadcasterSupport.java | 389 |
1 files changed, 389 insertions, 0 deletions
diff --git a/libjava/classpath/javax/management/NotificationBroadcasterSupport.java b/libjava/classpath/javax/management/NotificationBroadcasterSupport.java new file mode 100644 index 000000000..28b8148c1 --- /dev/null +++ b/libjava/classpath/javax/management/NotificationBroadcasterSupport.java @@ -0,0 +1,389 @@ +/* NotificationBroadcasterSupport.java -- Supporting implementation. + Copyright (C) 2007 Free Software Foundation, Inc. + +This file is part of GNU Classpath. + +GNU Classpath is free software; you can redistribute it and/or modify +it under the terms of the GNU General Public License as published by +the Free Software Foundation; either version 2, or (at your option) +any later version. + +GNU Classpath is distributed in the hope that it will be useful, but +WITHOUT ANY WARRANTY; without even the implied warranty of +MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU +General Public License for more details. + +You should have received a copy of the GNU General Public License +along with GNU Classpath; see the file COPYING. If not, write to the +Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA +02110-1301 USA. + +Linking this library statically or dynamically with other modules is +making a combined work based on this library. Thus, the terms and +conditions of the GNU General Public License cover the whole +combination. + +As a special exception, the copyright holders of this library give you +permission to link this library with independent modules to produce an +executable, regardless of the license terms of these independent +modules, and to copy and distribute the resulting executable under +terms of your choice, provided that you also meet, for each linked +independent module, the terms and conditions of the license of that +module. An independent module is a module which is not derived from +or based on this library. If you modify this library, you may extend +this exception to your version of the library, but you are not +obligated to do so. If you do not wish to do so, delete this +exception statement from your version. */ + +package javax.management; + +import gnu.javax.management.ListenerData; + +import java.util.ArrayList; +import java.util.Iterator; +import java.util.List; + +import java.util.concurrent.Executor; + +/** + * <p> + * Provides an implementation of the {@link NotificationEmitter} + * interface, which beans may utilise by extension. By default, + * a synchronous dispatch system is provided, whereby the + * {@link #handleNotification(NotificationListener, Notification, + * Object)} is called once per listener by + * {*@link #sendNotification(Notification)} before returning. + * Thus, unless the listener is remote, it will have received + * the notification before the method returns. + * This may be changed by overriding the <code>handleNotification</code> + * method, or by providing an {@link java.util.concurrent.Executor} to + * use. With the latter, the dispatch of a notification to a particular + * listener will form one task performed by the executor. + * </p> + * <p> + * Any exceptions thrown by the dispatch process will be caught, allowing + * other listeners to still receive the notification. However, any + * {@link Error}s that are thrown will be propogated to the caller of + * {@link #sendNotification(Notification)}. + * </p> + * + * @author Andrew John Hughes (gnu_andrew@member.fsf.org) + * @since 1.5 + */ +public class NotificationBroadcasterSupport + implements NotificationEmitter +{ + + /** + * The executor for dispatch, or + * <code>null</code> if this thread should + * handle dispatch itself. + */ + private Executor executor; + + /** + * An array containing information on each + * notification, or <code>null</code> if an + * empty array should be returned by + * {@link #getNotificationInfo()}. + */ + private MBeanNotificationInfo[] info; + + /** + * The list of listeners registered with + * this broadcaster. + */ + private final List<ListenerData> listeners = + new ArrayList<ListenerData>(); + + /** + * Constructs a {@link NotificationBroadcasterSupport} using + * the default synchronous dispatch model, where a single + * thread sends the notification to all listeners. This + * is equivalent to calling + * <code>NotificationBroadcasterSupport(null, null)</code>. + */ + public NotificationBroadcasterSupport() + { + this(null, (MBeanNotificationInfo[]) null); + } + + /** + * Constructs a {@link NotificationBroadcasterSupport} where + * the specified (@link java.util.concurrent.Executor} is used + * to perform each invocation of the + * {@link #handleNotification(NotificationListener, Notification, + * Object)} method. Filtering is performed beforehand, by this + * thread; only calls which have successfully passed through the + * filter are sent to the executor. This is equivalent to calling + * <code>NotificationBroadcasterSupport(executor, null)</code>. + * + * @param executor the executor to use for each call to + * <code>handleNotification()</code>. + * @since 1.6 + */ + public NotificationBroadcasterSupport(Executor executor) + { + this(executor, (MBeanNotificationInfo) null); + } + + /** + * Constructs a {@link NotificationBroadcasterSupport} using + * the default synchronous dispatch model, where a single + * thread sends the notification to all listeners. The specified + * {@link MBeanNotificationInfo} array is used to provide + * information about the notifications on calls to + * {@link #getNotificationInfo()}, where a clone will be + * returned if the array is non-empty. This is equivalent to + * calling <code>NotificationBroadcasterSupport(null, info)</code>. + * + * @param info an array of {@link MBeanNotificationInfo} objects + * describing the notifications delivered by this + * broadcaster. This may be <code>null</code>, which + * is taken as being equivalent to an empty array. + */ + public NotificationBroadcasterSupport(MBeanNotificationInfo... info) + { + this(null, info); + } + + /** + * Constructs a {@link NotificationBroadcasterSupport} where + * the specified (@link java.util.concurrent.Executor} is used + * to perform each invocation of the + * {@link #handleNotification(NotificationListener, Notification, + * Object)} method. Filtering is performed beforehand, by this + * thread; only calls which have successfully passed through the + * filter are sent to the executor. The specified + * {@link MBeanNotificationInfo} array is used to provide + * information about the notifications on calls to + * {@link #getNotificationInfo()}, where a clone will be + * returned if the array is non-empty. + * + * @param executor the executor to use for each call to + * <code>handleNotification()</code>. + * @param info an array of {@link MBeanNotificationInfo} objects + * describing the notifications delivered by this + * broadcaster. This may be <code>null</code>, which + * is taken as being equivalent to an empty array. + * @since 1.6 + */ + public NotificationBroadcasterSupport(Executor executor, + MBeanNotificationInfo... info) + { + this.executor = executor; + this.info = info; + } + + /** + * Registers the specified listener as a new recipient of + * notifications from this bean. If non-null, the filter + * argument will be used to select which notifications are + * delivered. The supplied object will also be passed to + * the recipient with each notification. This should not + * be modified by the broadcaster, but instead should be + * passed unmodified to the listener. + * + * @param listener the new listener, who will receive + * notifications from this broadcasting bean. + * @param filter a filter to determine which notifications are + * delivered to the listener, or <code>null</code> + * if no filtering is required. + * @param passback an object to be passed to the listener with + * each notification. + * @throws IllegalArgumentException if <code>listener</code> is + * <code>null</code>. + * @see #removeNotificationListener(NotificationListener) + */ + public void addNotificationListener(NotificationListener listener, + NotificationFilter filter, + Object passback) + throws IllegalArgumentException + { + if (listener == null) + throw new IllegalArgumentException("Null listener added to bean."); + listeners.add(new ListenerData(listener, filter, passback)); + } + + /** + * Returns an array describing the notifications this + * bean may send to its registered listeners. Ideally, this + * array should be complete, but in some cases, this may + * not be possible. However, be aware that some listeners + * may expect this to be so. + * + * @return the array of possible notifications. + */ + public MBeanNotificationInfo[] getNotificationInfo() + { + if (info == null || info.length == 0) + return new MBeanNotificationInfo[0]; + return (MBeanNotificationInfo[]) info.clone(); + } + + /** + * This method is called on a per-listener basis, either + * from this thread or the supplied executor, and may be + * overridden by subclasses which wish to change how + * notifications are delivered. The default + * implementation simply calls + * <code>listener.handleNotification(notif, passback)</code>. + * + * @param listener the listener to send the notification to. + * @param notif the notification to dispatch. + * @param passback the passback object of the listener. + */ + protected void handleNotification(NotificationListener listener, + Notification notif, + Object passback) + { + listener.handleNotification(notif, passback); + } + + /** + * Removes the specified listener from the list of recipients + * of notifications from this bean. This includes all combinations + * of filters and passback objects registered for this listener. + * For more specific removal of listeners, see the subinterface + * {@link NotificationEmitter}. + * + * @param listener the listener to remove. + * @throws ListenerNotFoundException if the specified listener + * is not registered with this bean. + * @see #addNotificationListener(NotificationListener, NotificationFilter, + * java.lang.Object) + */ + public void removeNotificationListener(NotificationListener listener) + throws ListenerNotFoundException + { + Iterator<ListenerData> it = listeners.iterator(); + boolean foundOne = false; + while (it.hasNext()) + { + if (it.next().getListener() == listener) + { + it.remove(); + foundOne = true; + } + } + if (!foundOne) + throw new ListenerNotFoundException("The specified listener, " + listener + + "is not registered with this bean."); + } + + /** + * Removes the specified listener from the list of recipients + * of notifications from this bean. Only the first instance with + * the supplied filter and passback object is removed. + * <code>null</code> is used as a valid value for these parameters, + * rather than as a way to remove all registration instances for + * the specified listener; for this behaviour instead, see the details + * of the same method in {@link NotificationBroadcaster}. + * + * @param listener the listener to remove. + * @param filter the filter of the listener to remove. + * @param passback the passback object of the listener to remove. + * @throws ListenerNotFoundException if the specified listener + * is not registered with this bean. + * @see #addNotificationListener(NotificationListener, NotificationFilter, + * java.lang.Object) + */ + public void removeNotificationListener(NotificationListener listener, + NotificationFilter filter, + Object passback) + throws ListenerNotFoundException + { + if (!(listeners.remove(new ListenerData(listener, filter, passback)))) + { + throw new ListenerNotFoundException("The specified listener, " + listener + + " with filter " + filter + + "and passback " + passback + + ", is not registered with this bean."); + } + } + + /** + * <p> + * Performs delivery of the notification. If an executor + * was specified on construction, this will be used to call + * {@link #handleNotification(NotificationListener, Notification, + * Object)}. If the executor is <code>null</code>, however, + * this thread calls the method itself in order to perform a + * synchronous dispatch of the notification to all eligible + * listeners. + * </p> + * <p> + * Prior to either process taking place, the listeners are filtered. + * Notifications are only delivered if the filter is either + * <code>null</code> or returns true from the + * {@link NotificationFilter#isNotificationEnabled(Notification)} + * method. + * </p> + * + * @param notif the notification to send. + */ + public void sendNotification(Notification notif) + { + for (ListenerData ldata : listeners) + { + NotificationFilter filter = ldata.getFilter(); + if (filter == null || filter.isNotificationEnabled(notif)) + { + if (executor == null) + try + { + handleNotification(ldata.getListener(), notif, + ldata.getPassback()); + } + catch (Exception e) { /* Ignore */ } + else + executor.execute(new DispatchTask(ldata, notif)); + } + } + } + + /** + * The dispatch task to be performed by an executor. + */ + private final class DispatchTask + implements Runnable + { + + /** + * The data on the listener being called. + */ + private ListenerData ldata; + + /** + * The notification to send. + */ + private Notification notif; + + /** + * Construct a new {@link DispatchTask}. + * + * @param ldata the listener data. + * @param notif the notification to send. + */ + public DispatchTask(ListenerData ldata, + Notification notif) + { + this.ldata = ldata; + this.notif = notif; + } + + /** + * Dispatch the notification. + */ + public void run() + { + try + { + handleNotification(ldata.getListener(), notif, + ldata.getPassback()); + } + catch (Exception e) { /* Ignore */ } + } + } + +} |