/* * Oscar - An implementation of the OSGi framework. * Copyright (c) 2004, Richard S. Hall * All rights reserved. *   * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: *   *   * Redistributions of source code must retain the above copyright *     notice, this list of conditions and the following disclaimer. *   * Redistributions in binary form must reproduce the above copyright *     notice, this list of conditions and the following disclaimer in *     the documentation and/or other materials provided with the *     distribution. *   * Neither the name of the ungoverned.org nor the names of its *     contributors may be used to endorse or promote products derived *     from this software without specific prior written permission. *   * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. *  * Contact: Richard S. Hall (heavy@ungoverned.org) * Contributor(s): ***/package org.ungoverned.oscar.util;import java.util.EventListener;import java.util.EventObject;import org.osgi.framework.BundleListener;import org.osgi.framework.ServiceListener;import org.osgi.framework.SynchronousBundleListener;import org.ungoverned.oscar.Oscar;/** * This is a subclass of <tt>DispatchQueue</tt> that specifically adds support * for <tt>SynchronousBundleListener</tt>s; the OSGi specification * says that synchronous bundle listeners should receive their events * immediately, i.e., they should not be delivered on a separate thread * like is the case with the <tt>DispatchQueue</tt>. To achieve this * functionality, this class overrides the dispatch method to automatically * fire any bundle events to synchronous bundle listeners using the * calling thread. In order to ensure that synchronous bundle listeners * do not receive an event twice, it wraps the passed in <tt>Dipatcher</tt> * instance so that it filters synchronous bundle listeners.**/public class OscarDispatchQueue extends DispatchQueue{    /**     * Dispatches an event to a set of event listeners using a specified     * dispatcher object. This overrides the definition of the super class     * to deliver events to <tt>ServiceListener</tt>s and     * <tt>SynchronousBundleListener</tt>s using     * the calling thread instead of the event dispatching thread. All     * other events are still delivered asynchronously.     *     * @param dispatcher the dispatcher used to actually dispatch the event; this     *          varies according to the type of event listener.     * @param clazz the class associated with the target event listener type;     *              only event listeners of this type will receive the event.     * @param eventObj the actual event object to dispatch.    **/    public void dispatch(Dispatcher dispatcher, Class clazz, EventObject eventObj)    {        Object[] listeners = getListeners();        // If this is an event for service listeners, then dispatch it        // immediately since service events are never asynchronous.        if ((clazz == ServiceListener.class) && (listeners.length > 0))        {            // Notify appropriate listeners.            for (int i = listeners.length - 2; i >= 0; i -= 2)            {                // If the original listener is a synchronous bundle listener                // or a service listener, then dispatch event immediately                // per the specification.                ListenerWrapper lw = (ListenerWrapper) listeners[i + 1];                if (lw.getListenerClass() == ServiceListener.class)                {                    try {                        dispatcher.dispatch(                            (EventListener) lw, eventObj);                    } catch (Throwable th) {                        Oscar.error("OscarDispatchQueue: Error during dispatch.", th);                    }                }            }        }        // Dispatch bundle events to synchronous bundle listeners immediately,        // but deliver to standard bundle listeners asynchronously.        else if ((clazz == BundleListener.class) && (listeners.length > 0))        {            // Notify appropriate listeners.            for (int i = listeners.length - 2; i >= 0; i -= 2)            {                // If the original listener is a synchronous bundle listener,                // then dispatch event immediately per the specification.                ListenerWrapper lw = (ListenerWrapper) listeners[i + 1];                if (lw.getListenerClass() == SynchronousBundleListener.class)                {                    try {                        dispatcher.dispatch(                            (EventListener) lw, eventObj);                    } catch (Throwable th) {                        Oscar.error("OscarDispatchQueue: Error during dispatch.", th);                    }                }            }            // Wrap the dispatcher so that it ignores synchronous            // bundle listeners since they have already been dispatched.            IgnoreSynchronousDispatcher ignoreDispatcher = new IgnoreSynchronousDispatcher();            ignoreDispatcher.setDispatcher(dispatcher);            // Dispatch the bundle listener asynchronously.            dispatch(listeners, ignoreDispatcher, clazz, eventObj);        }        // All other events are dispatched asynchronously.        else        {            dispatch(listeners, dispatcher, clazz, eventObj);        }    }    private static class IgnoreSynchronousDispatcher implements Dispatcher    {        private Dispatcher m_dispatcher = null;        public void setDispatcher(Dispatcher dispatcher)        {            m_dispatcher = dispatcher;        }        public void dispatch(EventListener l, EventObject eventObj)        {            if (l instanceof ListenerWrapper)            {                ListenerWrapper lw = (ListenerWrapper) l;                // Do not dispatch events to synchronous listeners,                // since they are dispatched immediately above.                if (!(lw.getListenerClass() == SynchronousBundleListener.class))                {                    m_dispatcher.dispatch(l, eventObj);                }            }        }    }}