distnodehandle.java

pastry的java实现的2.0b版

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

"FreePastry" Peer-to-Peer Application Development Substrate 

Copyright 2002, Rice University. All rights reserved.

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

package rice.pastry.dist;

import rice.pastry.*;
import rice.pastry.messaging.*;

import java.io.*;
import java.net.*;
import java.util.*;

/**
 * Abstract class for handles to "real" remote nodes. This class abstracts out
 * the node handle verification which is necessary in the "real" pastry
 * protocols, since NodeHandles are sent across the wire.
 *
 * @version $Id: DistNodeHandle.java 3274 2006-05-15 16:17:47Z jeffh $
 * @author Alan Mislove
 */
public abstract class DistNodeHandle extends NodeHandle implements Observer {
  // the nodeId of this node handle's remote node
  /**
   * DESCRIBE THE FIELD
   */
  protected Id nodeId;

  // the address (ip + port) of this node
  /**
   * DESCRIBE THE FIELD
   */
  protected InetSocketAddress address;

  /**
   * a unique number matching the liveness of this node this number will be
   * different each time the process is run, but the NodeId can be the same.
   */
  protected int epoch;
  final static long serialVersionUID = 6030505652558872412L;

  /**
   * Constructor
   *
   * @param nodeId This node handle's node Id.
   * @param address DESCRIBE THE PARAMETER
   */
  public DistNodeHandle(Id nodeId, InetSocketAddress address) {
    this.nodeId = nodeId;
    this.address = address;
    // note that we always want the epoch to be random, there is no reason to ever
    // use a specifiable randomsource for this
    epoch = new Random().nextInt();
  }

  /**
   * Gets the nodeId of this Pastry node.
   *
   * @return the node id.
   */
  public final Id getNodeId() {
    return nodeId;
  }

  /**
   * Gets the epoch or session identifier of this Pastry node.
   *
   * @return the epoch.
   */
  public int getEpoch() {
    return epoch;
  }

  /**
   * Returns the IP address and port of the remote node.
   *
   * @return The InetSocketAddress of the remote node.
   */
  public final InetSocketAddress getAddress() {
    return address;
  }

  /**
   * Returns a String representation of this DistNodeHandle. This method is
   * designed to be called by clients using the node handle, and is provided in
   * order to ensure that the right node handle is being talked to.
   *
   * @return A String representation of the node handle.
   */
  public abstract String toString();

  /**
   * Equivalence relation for nodehandles. They are equal if and only if their
   * corresponding NodeIds are equal.
   *
   * @param obj the other nodehandle .
   * @return true if they are equal, false otherwise.
   */
  public abstract boolean equals(Object obj);

  /**
   * Hash codes for node handles. It is the hashcode of their corresponding
   * NodeId's.
   *
   * @return a hash code.
   */
  public abstract int hashCode();
}