gossipservice.java

JXTA&#8482 is a set of open, generalized peer-to-peer (P2P) protocols that allow any networked devi

/*
 * Copyright (c) 2004-2007 Sun Microsystems, Inc.  All rights reserved.
 *
 *  The Sun Project JXTA(TM) Software License
 *
 *  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.
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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 Sun Microsystems, Inc. for JXTA(TM) technology." 
 *     Alternately, this acknowledgment may appear in the software itself, if
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 *  States and other countries.
 *
 *  Please see the license information page at :
 *  <http://www.jxta.org/project/www/license.html> for instructions on use of
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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.
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package tutorial.customgroupservice;

import java.io.IOException;
import java.net.URI;
import java.util.NoSuchElementException;
import java.util.Timer;
import java.util.TimerTask;
import java.util.logging.Level;
import java.util.logging.Logger;
import net.jxta.document.Advertisement;
import net.jxta.document.AdvertisementFactory;
import net.jxta.document.XMLDocument;
import net.jxta.endpoint.EndpointAddress;
import net.jxta.endpoint.EndpointService;
import net.jxta.endpoint.Message;
import net.jxta.endpoint.MessageElement;
import net.jxta.endpoint.StringMessageElement;
import net.jxta.exception.PeerGroupException;
import net.jxta.id.ID;
import net.jxta.logging.Logging;
import net.jxta.platform.ModuleSpecID;
import net.jxta.peergroup.PeerGroup;
import net.jxta.platform.Module;
import net.jxta.platform.ModuleClassID;
import net.jxta.protocol.ConfigParams;
import net.jxta.protocol.ModuleImplAdvertisement;
import net.jxta.service.Service;

/**
 *  A very simple Peer Group Service.
 *  <p/>
 *  This service sends JXTA an annoucement message every few seconds via
 *  JXTA endpoint service <tt>propagate()</tt>. It also listens for announcement
 *  messages from other peers and prints a message on the console whenever it
 *  receives one.
 *  <p/>
 *  The protocol for this service consists of JXTA messages sent via Endpoint
 *  propagation. This gossip service implementation uses the <tt>assignedID</tt>
 *  which is initialized in the <tt>init()</tt> method as the endpoint address
 *  for the messages it sends and receives. Use of the <tt>assignedID</tt> as
 *  the <tt>serviceParam</tt> is a common choice because it is gauranteed to be
 *  unique within the PeerGroup and the <tt>assignedID</tt>
 *  <tt>serviceParam</tt> is informally reserved for the service with that
 *  <tt>assignedID</tt>.
 *  <p/>The messages exchanged by the gossip service contain two message
 *  elements in the "<tt>gossip</tt>" namespace. "<tt>sender</tt>" contains a
 *  <tt>String</tt> of the peer id of the message sender. "<tt>gossip</tt>"
 *  contains a <tt>String</tt> of the gossip text which is being shared by the
 *  sender.
 */
public class GossipService implements net.jxta.service.Service, net.jxta.endpoint.EndpointListener {

    /**
     * Logger
     */
    private static final transient Logger LOG = Logger.getLogger(GossipService.class.getName());
    /**
     *  The module class ID for Gossip services. All Gossip services regardless
     *  of the protocol used share this same module class id.
     */
    public static final ModuleClassID GOSSIP_SERVICE_MCID = ModuleClassID.create(URI.create("urn:jxta:uuid-4CD1574ABA614A5FA242B613D8BAA30F05"));
    /**
     *  The module spec ID for our Gossip service. The module spec id contains
     *  the {@code GOSSIP_SERVICE_MCID}. All implementations which use the
     *  same messaging protocol as this implementation will share this same
     *  module spec id.
     */
    public static final ModuleSpecID GOSSIP_SERVICE_MSID = ModuleSpecID.create(URI.create("urn:jxta:uuid-4CD1574ABA614A5FA242B613D8BAA30FD0A45F5F0E1A450DA912BB01585AB0FC06"));
    /**
     *  The default gossip text we will send to other peers.
     */
    public static final String DEFAULT_GOSSIP_TEXT = "JXTA is cool. Pass it on!";
    /**
     *  Whether we should show our own gossip text default.
     */
    public static final boolean DEFAULT_SHOW_OWN = false;
    /**
     *  The default interval in milliseconds at which we will send our gossip
     *  text.
     */
    public static final long GOSSIP_INTERVAL_DEFAULT = 10 * 1000L;
    /**
     *  The name of the message namespace for all gossip service messages.
     */
    public static final String GOSSIP_NAMESPACE = "gossip";
    /**
     *  The name of the message element identifying the gossip sender.
     */
    public static final String GOSSIP_SENDER_ELEMENT_NAME = "sender";
    /**
     *  The name of the message element containing the gossip text.
     */
    public static final String GOSSIP_GOSSIP_ELEMENT_NAME = "gossip";
    /**
     *  A Timer shared between all Gossip service instances that we use for
     *  sending our gossip messages.
     */
    public static final Timer SHARED_TIMER = new Timer("Gossip Services Timer", true);
    /**
     *  The peer group in which this instance is running.
     */
    private PeerGroup group;
    /**
     * Our assigned service ID. Usually this is our MCID but may also be our
     * MCID with a role id if there are multiple gossip services within the
     * peer group.
     */
    private ID assignedID;
    /**
     *  The module implementation advertisement for our instance.
     */
    private ModuleImplAdvertisement implAdv;
    /**
     *  The "gossip" message we read from our configuration.
     */
    private String gossip = DEFAULT_GOSSIP_TEXT;
    /**
     *  If {@code true} then we show our own gossip messages;
     */
    private boolean showOwn = DEFAULT_SHOW_OWN;
    /**
     *  The interval in milliseconds at which we will send our gossip message.
     */
    private long gossip_interval = GOSSIP_INTERVAL_DEFAULT;
    /**
     * The endpoint service with which we send our gossips and register our
     * listener.
     */
    private EndpointService endpoint = null;
    /**
     *  The timer task we use to send our gossip messages.
     */
    private TimerTask sendTask = null;

    /**
     * {@inheritDoc}
     * <p/>
     * This implementation doesn't currently use interface objects so it just
     * returns itself. We would use an interface object if we needed to maintain
     * state for each caller of the Gossip Service or wished to attach a
     * security context to the callers of this service. ie. different callers
     * might have different sercurity privleges.
     */
    public Service getInterface() {
        return this;
    }

    /**
     * Return our assigned ID.
     *
     * @return Our assigned ID.
     */
    public ID getAssignedID() {