abstractpinghandler.java

Java p2p程序设计2002年版

package net.jxta.impl.shell.bin.ping;


import java.io.*;
import net.jxta.exception.*;
import net.jxta.discovery.*;
import net.jxta.endpoint.*;
import net.jxta.pipe.*;
import net.jxta.peergroup.*;
import net.jxta.document.*;
import net.jxta.id.*;
import net.jxta.protocol.*;
import java.util.*;

/**
 * This abstract class factors out the common behavior of all ping handler types.
 * Namely, creating a thread, listening on a particular pipe and dispatching
 * the pipe Message and timestamp to an abstract method.
 */
public abstract class AbstractPingHandler implements Runnable {

    InputPipe pipe;
    Thread thread ;
    
    public AbstractPingHandler(InputPipe pipe) {
        this.pipe = pipe;
    }
    
    public void abort() {
        thread.interrupt();
    }
    
    /**
     * Spawn a thread and wait for a ping message to arrive.
     */
    public void waitForMessage() {
        thread = new Thread(this);
        thread.start();
    }
    
    public void run() {
            Message msg = null;

            long timestamp;
            
            while(true) {
                try {
                    msg = pipe.waitForMessage();                    
                    // Arrival timestamp              
                    timestamp = new Date().getTime();
                    if (msg == null) {
                        if (Thread.interrupted()) {
                            pipe.close();
                            return;
                        }
                    }
                } catch (Exception e) {
                    e.printStackTrace();
                    pipe.close();
                    return;
                }
                deliverMessage(msg,timestamp);
            }
    }    
    
    /**
     * This key method is abstractly declared in AbstractPingHandler which
     * delegates to subclasses here.
     * @param msg The Message object received on the pipe
     * @param timestamp The timestamp the message was received on the pipe
     */
    protected abstract void deliverMessage(Message msg, long timestamp);
    
}