listeneradaptor.java

jxta_src_2.41b jxta 2.41b 最新版源码 from www.jxta.org

/*
 *
 * $Id: ListenerAdaptor.java,v 1.3 2004/05/24 18:34:53 jice Exp $
 *
 * Copyright (c) 2004 Sun Microsystems, Inc.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. 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.
 *
 * 3. The end-user documentation included with the redistribution,
 *    if any, must include the following acknowledgment:
 *       "This product includes software developed by the
 *       Sun Microsystems, Inc. for Project JXTA."
 *    Alternately, this acknowledgment may appear in the software itself,
 *    if and wherever such third-party acknowledgments normally appear.
 *
 * 4. The names "Sun", "Sun Microsystems, Inc.", "JXTA" and "Project JXTA"
 *    must not be used to endorse or promote products derived from this
 *    software without prior written permission. For written
 *    permission, please contact Project JXTA at http://www.jxta.org.
 *
 * 5. Products derived from this software may not be called "JXTA",
 *    nor may "JXTA" appear in their name, without prior written
 *    permission of Sun.
 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED 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 SUN MICROSYSTEMS OR
 * ITS 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.
 *
 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of Project JXTA.  For more
 * information on Project JXTA, please see
 * <http://www.jxta.org/>.
 *
 * This license is based on the BSD license adopted by the Apache Foundation.
 */
package net.jxta.endpoint;

import net.jxta.util.SimpleSelectable;
import net.jxta.util.SimpleSelector;

import org.apache.log4j.Level;
import org.apache.log4j.Logger;

import java.io.IOException;
import java.util.List;
import java.util.ArrayList;
import java.util.Map;
import java.util.HashMap;
import java.util.Iterator;

/*
 * The legacy getMessenger asynchronous API never returns any object to the invoker until a messenger could actually be made,
 * allowing the application to supply a listener to be invoked when the operation completes. The legacy Messenger API also
 * provides a method to send messages that calls a listener to report the outcome of the operation.  <p/> 
 *
 * The model has changed, so that an asynchronous messenger is made unresolved and returned immediately to the invoker, which can
 * then request opening or even just send a message to force the opening. Subsequently, the messenger can be used as a control
 * block to monitor progress with {@link Messenger#register} and {@link Messenger#waitState}.<p/>
 *
 * Likewise, the outcome of sending a message is a property of that message. Messages can be selected to monitor property changes
 * with {@link Message#register} and {@link Message#getMessageproperty} (the outcome property key is
 * <code>Messenger.class</code>).<p/>
 *
 * This class here provides the legacy listener model on top of the new model for applications that prefere listeners. This class
 * is used internally to emulate the legacy listener behaviour, so that applications do not need to be adapted.<p/>
 *
 * Note: one instance of this class gets instantiated by each EndpointService interface. However, it does not start using any
 * resources until it first gets used.<p/>
 */

public class ListenerAdaptor implements Runnable {

    // FIXME - [e-mail] 20040413: Eventhough it is not as critical as it used to be we should get rid of old, never resolved entries..
    // Attempts are supposed to always fail or succeed rather soon. Here, we trust transports in that matter. Is it safe ?

    /**
     *  Log4J Category
     **/
    private static final Logger LOG = Logger.getLogger(ListenerAdaptor.class.getName());

    HashMap inprogress = null;

    /**
     * The thread that does the work.
     **/
    private Thread bgThread = null;

    /**
     * The selector that we use to watch messengers progress.
     **/
    private SimpleSelector selector = null;

    /**
     * Are we asked to stop ?
     **/
    private boolean stopped = false;

    /**
     * The threadgroup that we use.
     **/
    private ThreadGroup threadGroup = null;

    public ListenerAdaptor(ThreadGroup threadGroup) {
        this.threadGroup = threadGroup;
    }

    private void stop() {

        stopped = true;

        // Stop the thread if it was ever created.
        if (bgThread != null) {
            bgThread.interrupt();
            bgThread = null;
        }
    }

    // Cannot be re-started. Do not call once stopped.

    private void init() {

        if (bgThread != null) {
            return;
        }

        inprogress = new HashMap(32);

        selector = new SimpleSelector();

        bgThread = new Thread(threadGroup,
                              this,
                              "Listener Adaptor");
        bgThread.setDaemon(true);
        bgThread.start();
    }

    public void shutdown() {
        synchronized(this) {
            stop();
        }
    }

    /**
     * Stop watching a given selectable.
     **/
    private void forgetSelectable(SimpleSelectable ts) {
        // Either way, we're done with this one.
        ts.unregister(selector);

        synchronized(this) {
            inprogress.remove(ts.getIdentityReference());
        }
    }

    /**
     * Select the given message and invoke the given listener when the message sending is complete.
     *
     * @param listener The listener to invoke. If null the resolution will take place, but obviously no listener will be invoked.
     * @param m The message being sent.
     * @return true if the message was registered succesfully or the listener is null. If true it is guaranteed that the listener
     * will be invoked unless null. If false, it is guaranteed that the listener will not be invoked.
     **/
    public boolean watchMessage( OutgoingMessageEventListener listener, Message m ) {
        synchronized(this) {

            if (stopped) {
                return false;
            }

            if (listener == null) {
                // We're done, then. The invoker does not really care.
                return true;
            }

            // Init if needed.
            init();

            // First we must ensure that if the state changes we'll get to handle it.
            ListenerContainer allListeners = (ListenerContainer) inprogress.get(m.getIdentityReference());
            if (allListeners == null) {
                // Use ArrayList. The code is optimized for that.
                allListeners = new MessageListenerContainer();
                inprogress.put(m.getIdentityReference(), allListeners);
            }
            allListeners.add(listener);
        }

        // When we do that, the selector get notified. Therefore we will always check the initial state automatically. If the
        // selectable is already done with, the listener will be called by the selector's handler.
        m.register(selector);

        return true;
    }

    /**
     * Select the given messenger and invoke the given listener when the messenger is resolved.