endpointserviceinterface.java

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

/*
 * Copyright (c) 2001 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
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 * 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.
 *
 * $Id: EndpointServiceInterface.java,v 1.23 2004/05/24 18:34:55 jice Exp $
 */

package net.jxta.impl.endpoint;

import java.io.IOException;
import java.lang.ref.Reference;
import java.lang.ref.WeakReference;
import java.util.Iterator;
import java.util.WeakHashMap;

import net.jxta.document.Advertisement;
import net.jxta.endpoint.EndpointService;
import net.jxta.endpoint.Message;
import net.jxta.endpoint.EndpointAddress;
import net.jxta.endpoint.EndpointListener;
import net.jxta.endpoint.MessageFilterListener;
import net.jxta.endpoint.EndpointListener;
import net.jxta.endpoint.MessengerEventListener;
import net.jxta.endpoint.ChannelMessenger;
import net.jxta.endpoint.Messenger;
import net.jxta.endpoint.MessageTransport;
import net.jxta.endpoint.ListenerAdaptor;
import net.jxta.id.ID;
import net.jxta.peergroup.PeerGroup;
import net.jxta.service.Service;

import net.jxta.exception.PeerGroupException;

import net.jxta.impl.util.TimeUtils;

/**
 * The EndpointService Service provides a frontend API and enviroment to all
 * endpoint protocols.
 *
 */

public class EndpointServiceInterface implements EndpointService {
    
    EndpointServiceImpl theRealThing = null;

    /**
     * The object that emulates the legacy send-message-with-listener and get-messenger-with-listener APIs.
     **/
    private ListenerAdaptor listenerAdaptor = null;

    /**
     * The cache of channels. If a given owner of this EndpointService interface object requests channels for the same exact
     * destination multiple times, we will return the same channel object as much as possible.  We keep channels in a weak map, so
     * that when channels are discarded, they eventually disappear.  Channels that have messages in them are always
     * referenced. Therefore, this prevents the creation of more than one channel with messages in it for the same destination in
     * the same context (owner of interface object - typically one module). This is required to properly support the common (and convenient) pattern:<p/>
     *
     * <code>m = endpIntf.getMessenger(); m.sendMessage(); m = null;</code><p/>
     *
     * If that was not kept in check, it would be possible to inadvertently create an infinite number of channels with pending
     * messages, thus an infinite number of messages too.
     **/
    private WeakHashMap channelCache = new WeakHashMap();

    /**
     * Builds a new interface object.
     **/
    public EndpointServiceInterface(EndpointServiceImpl s) {
        theRealThing = s;
        this.listenerAdaptor = new ListenerAdaptor(theRealThing.getGroup().getHomeThreadGroup());
    }
    
    /**
     * {@inheritDoc}
     *
     *  <p/>FIXME: This is meaningless for the interface object;
     * it is there only to satisfy the requirements of the
     * interface that we implement. Ultimately, the API should define
     * two levels of interfaces: one for the real service implementation
     * and one for the interface object. Right now it feels a bit heavy
     * to so that since the only different between the two would be
     * init() and may-be getName().
     */
    
    public void init(PeerGroup pg, ID id, Advertisement ia) {
    }
    
    /**
     * {@inheritDoc}
     *
     * This is here for temporary class hierarchy reasons.
     * it is ALWAYS ignored. By definition, the interface object
     * protects the real object's start/stop methods from being called
     */
    public int startApp(String[] arg) {
        return 0;
    }
    
    /**
     * {@inheritDoc}
     *
     * <p/>This is here for temporary class hierarchy reasons.
     * it is ALWAYS ignored. By definition, the interface object
     * protects the real object's start/stop methods from being called
     *
     * <p/>This request is currently ignored.
     */
    public void stopApp() {
    }
    
    /**
     * {@inheritDoc}
     **/
    public Advertisement getImplAdvertisement() {
        return theRealThing.getImplAdvertisement();
    }
    
    /**
     * {@inheritDoc}
     *
     * Sort of absurd but this is part of the API we're implementing.
     * We would not do a two-level API just for that.
     */
    public Service getInterface() {
        return this;
    }
    
    /**
     * {@inheritDoc}
     **/
    public PeerGroup getGroup() {
        return theRealThing.getGroup();
    }
    
    /**
     * {@inheritDoc}
     */
    public Messenger getCanonicalMessenger( EndpointAddress addr, Object hint ) {
        // XXX: maybe we should enforce the stripping of the address here.
        // That would prevent application from making canonical messengers with a variety of service names and
        // service params. On the other hand that would cost useless cloning of endp addrs and prevent future
        // flexibility regarding QOS params, possibly. Be liberal for now.
        return theRealThing.getCanonicalMessenger( addr, hint );
    }

    /**
     * {@inheritDoc}
     **/
    public Messenger getMessengerImmediate( EndpointAddress addr, Object hint ) {
        
        // Note: for now, the hint is not used for canonicalization (hint != QOS).
        synchronized(this) {
            Reference existing = (Reference) channelCache.get(addr);
            if (existing != null) {
                Messenger m = (Messenger) existing.get();
                if ((m != null) && ((m.getState() & Messenger.USABLE) != 0)) {
                    return m;
                }
            }
        }

        // We do not have a good one at hand. Make a new one.

        // Use the stripped address to get a canonical msngr; not doing so
        // would reduce the sharing to almost nothing.
        EndpointAddress plainAddr = new EndpointAddress(addr, null, null);

        Messenger found = theRealThing.getCanonicalMessenger( plainAddr, hint );

        // Address must not be a supported one.
        if (found == null) {
            return null;
        }

        // Get a channel for that servicename and serviceparam. redirect to this grp.

        // NOTE: This assumes that theRealThing.getGroup() is really the group where the application that obtained
        // this interface object lives. This is the case today because all groups have their own endpoint service.