myscribeclient.java

pastry的java实现的2.0b版

/*************************************************************************

"FreePastry" Peer-to-Peer Application Development Substrate 

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********************************************************************************/
/*
 *  Created on May 4, 2005
 */
package rice.tutorial.lesson6;

import rice.p2p.commonapi.*;
import rice.p2p.commonapi.Application;
import rice.p2p.commonapi.CancellableTask;
import rice.p2p.commonapi.Endpoint;
import rice.p2p.commonapi.Id;
import rice.p2p.commonapi.Message;
import rice.p2p.commonapi.NodeHandle;
import rice.p2p.commonapi.RouteMessage;
import rice.p2p.scribe.Scribe;
import rice.p2p.scribe.ScribeClient;
import rice.p2p.scribe.ScribeContent;
import rice.p2p.scribe.ScribeImpl;
import rice.p2p.scribe.Topic;
import rice.pastry.commonapi.PastryIdFactory;

/**
 * We implement the Application interface to receive regular timed messages (see
 * lesson5). We implement the ScribeClient interface to receive scribe messages
 * (called ScribeContent).
 *
 * @version $Id: pretty.settings 2305 2005-03-11 20:22:33Z jeffh $
 * @author Jeff Hoye
 */
public class MyScribeClient implements ScribeClient, Application {

  /**
   * The message sequence number. Will be incremented after each send.
   */
  int seqNum = 0;

  /**
   * This task kicks off publishing and anycasting. We hold it around in case we
   * ever want to cancel the publishTask.
   */
  CancellableTask publishTask;

  /**
   * My handle to a scribe impl.
   */
  Scribe myScribe;

  /**
   * The only topic this appl is subscribing to.
   */
  Topic myTopic;

  /**
   * The Endpoint represents the underlieing node. By making calls on the
   * Endpoint, it assures that the message will be delivered to a MyApp on
   * whichever node the message is intended for.
   */
  protected Endpoint endpoint;

  /**
   * The constructor for this scribe client. It will construct the
   * ScribeApplication.
   *
   * @param node the PastryNode
   */
  public MyScribeClient(Node node) {
    // you should recognize this from lesson 3
    this.endpoint = node.buildEndpoint(this, "myinstance");
    // construct Scribe
    myScribe = new ScribeImpl(node, "lesson6instance");
    // construct the topic
    myTopic = new Topic(new PastryIdFactory(node.getEnvironment()), "example topic");
    System.out.println("myTopic = " + myTopic);
    endpoint.register();
  }


  /**
   * Some passthrough accessors for the myScribe ************
   *
   * @return The Root value
   */
  public boolean isRoot() {
    return myScribe.isRoot(myTopic);
  }

  /**
   * Gets the Parent attribute of the MyScribeClient object
   *
   * @return The Parent value
   */
  public NodeHandle getParent() {
    // NOTE: Was just added to the Scribe interface.  May need to cast myScribe to a
    // ScribeImpl if using 1.4.1_01 or older.
    return ((ScribeImpl) myScribe).getParent(myTopic);
    //return myScribe.getParent(myTopic);
  }

  /**
   * Gets the Children attribute of the MyScribeClient object
   *
   * @return The Children value
   */
  public NodeHandle[] getChildren() {
    return myScribe.getChildren(myTopic);
  }

  /**
   * Subscribes to myTopic.
   */
  public void subscribe() {
    myScribe.subscribe(myTopic, this);
  }

  /**
   * Starts the publish task.
   */
  public void startPublishTask() {
    publishTask = endpoint.scheduleMessage(new PublishContent(), 5000, 5000);
  }


  /**
   * Part of the Application interface. Will receive PublishContent every so
   * often.
   *
   * @param id DESCRIBE THE PARAMETER
   * @param message DESCRIBE THE PARAMETER
   */
  public void deliver(Id id, Message message) {
    if (message instanceof PublishContent) {
      sendMulticast();
      sendAnycast();
    }
  }

  /**
   * Sends the multicast message.
   */
  public void sendMulticast() {
    System.out.println("Node " + endpoint.getLocalNodeHandle() + " broadcasting " + seqNum);
    MyScribeContent myMessage = new MyScribeContent(endpoint.getLocalNodeHandle(), seqNum);
    myScribe.publish(myTopic, myMessage);
    seqNum++;
  }

  /**
   * Called whenever we receive a published message.
   *
   * @param topic DESCRIBE THE PARAMETER
   * @param content DESCRIBE THE PARAMETER
   */
  public void deliver(Topic topic, ScribeContent content) {
    System.out.println("MyScribeClient.deliver(" + topic + "," + content + ")");
  }

  /**
   * Sends an anycast message.
   */
  public void sendAnycast() {
    System.out.println("Node " + endpoint.getLocalNodeHandle() + " anycasting " + seqNum);
    MyScribeContent myMessage = new MyScribeContent(endpoint.getLocalNodeHandle(), seqNum);
    myScribe.anycast(myTopic, myMessage);
    seqNum++;
  }

  /**
   * Called when we receive an anycast. If we return false, it will be delivered
   * elsewhere. Returning true stops the message here.
   *
   * @param topic DESCRIBE THE PARAMETER
   * @param content DESCRIBE THE PARAMETER
   * @return DESCRIBE THE RETURN VALUE
   */
  public boolean anycast(Topic topic, ScribeContent content) {
    boolean returnValue = myScribe.getEnvironment().getRandomSource().nextInt(3) == 0;
    System.out.println("MyScribeClient.anycast(" + topic + "," + content + "):" + returnValue);
    return returnValue;
  }

  /**
   * DESCRIBE THE METHOD
   *
   * @param topic DESCRIBE THE PARAMETER
   * @param child DESCRIBE THE PARAMETER
   */
  public void childAdded(Topic topic, NodeHandle child) {
//    System.out.println("MyScribeClient.childAdded("+topic+","+child+")");
  }

  /**
   * DESCRIBE THE METHOD
   *
   * @param topic DESCRIBE THE PARAMETER
   * @param child DESCRIBE THE PARAMETER
   */
  public void childRemoved(Topic topic, NodeHandle child) {
//    System.out.println("MyScribeClient.childRemoved("+topic+","+child+")");
  }

  /**
   * DESCRIBE THE METHOD
   *
   * @param topic DESCRIBE THE PARAMETER
   */
  public void subscribeFailed(Topic topic) {
//    System.out.println("MyScribeClient.childFailed("+topic+")");
  }

  /**
   * DESCRIBE THE METHOD
   *
   * @param message DESCRIBE THE PARAMETER
   * @return DESCRIBE THE RETURN VALUE
   */
  public boolean forward(RouteMessage message) {
    return true;
  }


  /**
   * DESCRIBE THE METHOD
   *
   * @param handle DESCRIBE THE PARAMETER
   * @param joined DESCRIBE THE PARAMETER
   */
  public void update(NodeHandle handle, boolean joined) {

  }

  /**
   * DESCRIBE THE CLASS
   *
   * @version $Id: pretty.settings 2305 2005-03-11 20:22:33Z jeffh $
   * @author jeffh
   */
  class PublishContent implements Message {
    /**
     * Gets the Priority attribute of the PublishContent object
     *
     * @return The Priority value
     */
    public byte getPriority() {
      return MAX_PRIORITY;
    }
  }

}