channelmessenger.java

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

/*
 *
 * $Id: ChannelMessenger.java,v 1.4 2005/08/08 19:59:05 bondolo Exp $
 *
 * Copyright (c) 2004 Sun Microsystems, Inc.  All rights reserved.
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 *    distribution.
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 * 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
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 * 5. Products derived from this software may not be called "JXTA",
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 * ====================================================================
 *
 * 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.peergroup.PeerGroupID;

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

/**
 * A Channel Messenger provides an exclusive interface to the shared messenger. 
 *
 * <p/>What is typically exclusive is the message queue, addressing parameters 
 * that are not usefully shared (serviceName, serviceParam), and if needed 
 * cross-group address rewritting parameters.
 *
 * <p/>This class is provided as a base for implementing such channel messengers, 
 * which are typically what Messenger.getChannelMessenger() needs to return. 
 *
 * @see net.jxta.endpoint.EndpointService
 * @see net.jxta.endpoint.EndpointAddress
 * @see net.jxta.endpoint.Message
 **/
public abstract class ChannelMessenger extends AbstractMessenger implements Messenger {

    /**
     * insertedServicePrefix This is how all valid inserted services start. This 
     * lets us recognize if a message already has an inserted service. Then we 
     * must not add another one. Only the top-most one counts.  Since insertion 
     * is only done here, the constant is defined here. Even if historically it 
     * was done within the endpoint implementation, it has become a protocol now.
     **/
    public static final String InsertedServicePrefix = "EndpointService:";

    private String insertedService;

    /**
     * The worker that implements sendMessage-with-listener for this channel. If
     * there's none, sendMessage-with-listener will throw an exception. Channels 
     * returned by getMessenger methods all have one already. It is up to the 
     * invoker of getChannelMessenger to supply one or not.
     **/
    private ListenerAdaptor messageWatcher;

    protected String origService;
    
    protected String origServiceParam;
    
    /**
     * Figure out what the service string will be after mangling (if required) 
     * and applying relevant defaults.
     *
     * @param service The service name in the unmangled address.
     * @return String The service name in the mangled address.
     **/
    protected String effectiveService( String service ) {

        // No redirection required. Just apply the default service.
        if (insertedService == null) {
            return (service == null) ? origService : service;
        }

        // Check if redirection is applicable.
        return ((service != null) && service.startsWith(InsertedServicePrefix)) ? service : insertedService;
    }

    /**
     * Figure out what the param string will be after mangling (if required) and 
     * applying relevant defaults.
     *
     * @param service The service name in the unmangled address.
     * @param serviceParam The service parameter in the unmangled address.
     * @return String The service parameter in the mangled address.
     **/
    protected String effectiveParam( String service, String serviceParam ) {

        // No redirection required. Or not applicable. Just apply the default param.
        if ((insertedService == null) || ((service != null) && service.startsWith(InsertedServicePrefix))) {
            return (serviceParam == null) ? origServiceParam : serviceParam;
        }

        // Apply redirection. We need the effective service, now.
        if (service == null) {
            service = origService;
        }

        if (serviceParam == null) {
            serviceParam = origServiceParam;
        }

        return ((null != service) && (null != serviceParam)) ? (service + "/" + serviceParam) : service;
    }

    /**
     * Give this channel the watcher that it must use whenever sendMessage(...,listener) is used. If not set,
     * sendMessage(..., listener) will throw.
     * @deprecated This method is in support of deprecated methods.
     **/
    public void setMessageWatcher( ListenerAdaptor messageWatcher ) {
        this.messageWatcher = messageWatcher;
    }

    /**
     * Create a new ChannelMessenger
     * 
     * @param baseAddress The network address messages go to; regardless of service, param, or group.
     * @param groupRedirection Group to which the messages must be redirected. This is used to implement the automatic group
     * seggregation which has become a de-facto standard. If not null, the unique portion of the specified groupID is
     * prepended with {@link #InsertedServicePrefix} and inserted in every message's destination address in place of the
     * the original service name, which gets shifted into the begining of the service parameter. The opposite is done
     * on arrival to restore the original destination address before the message is delivered to the listener in the
     * the specified group. Messages that already bear a group redirection are not affected.
     * @param origService The default destination service for messages sent without specifying a different service.
     * @param origServiceParam The default destination service parameter for messages sent without specifying a different service
     * parameter.
     **/
    public ChannelMessenger( EndpointAddress baseAddress, PeerGroupID groupRedirection,
                             String origService, String origServiceParam ) {


        // FIXME: The inserted service business is really messy. Group seggregation does not have to be the endpoint service's
        // business. It should be specified by the app as part of the destination address. What we're doing here
        // is simply enforcing what could just be a convention.

        super(baseAddress);
        if (groupRedirection == null) {
            insertedService = null;
        } else {
            insertedService = InsertedServicePrefix + groupRedirection.getUniqueValue().toString();
        }
        this.origService = origService;
        this.origServiceParam = origServiceParam;

        // Now that we're initialized enough, grab the destination addr from our superclass and fix it.  We add the service and
        // param; NOT the group mangling: getDestinationAddress[Object]() should always return what was given at construction.
        EndpointAddress dest = getDestinationAddressObject();
        dest.setServiceName(origService);
        dest.setServiceParameter(origServiceParam);
    }
    
    /**
     * {@inheritDoc}
     *
     * <p/> By default a channel refuses to make a channel.
     *
     **/
    public Messenger getChannelMessenger( PeerGroupID redirection, String service, String serviceParam ) {
        return null;
    }
    
    /**
     * {@inheritDoc}
     *
     * @deprecated Implements deprecated method.
     **/
    public void sendMessage(Message msg, String service, String serviceParam, OutgoingMessageEventListener listener) {
        if (messageWatcher == null) {
            throw new UnsupportedOperationException("This channel was not configured to emulate this legacy method.");
        }

        // Cleanup the message from any existing result prop since we're going to use select.
        msg.setMessageProperty(Messenger.class, null);

        // Tell the watcher to select that message.
        messageWatcher.watchMessage(listener, msg);

        sendMessageN(msg, service, serviceParam);
    }
}