selectpeer.java

基于jxta的文件共享和聊天系统源代码,下载下来分析吧

/*
 * Created on 7-set-2005
 *
 *  
 */

/**
 * @author magowiz
 *
 */
package p2p_system;
import java.io.IOException;
import java.util.Enumeration;

import net.jxta.discovery.DiscoveryEvent;
import net.jxta.discovery.DiscoveryListener;
import net.jxta.discovery.DiscoveryService;
import net.jxta.document.Advertisement;
import net.jxta.id.ID;
import net.jxta.peergroup.PeerGroup;
import net.jxta.protocol.DiscoveryResponseMsg;
import net.jxta.protocol.PeerAdvertisement;


public class SelectPeer implements DiscoveryListener {
	private ID [] pids ;
	private int pidx,idx;
	private PeerGroup pg;
	private DiscoveryService discoSvc;
	private int N;
	private PeerAdvertisement padv;
	
	
	public SelectPeer(PeerGroup p,int n)
	{
		pg=p;
		padv=pg.getPeerAdvertisement();
		discoSvc=pg.getDiscoveryService();		
		discoSvc.addDiscoveryListener(this);
		pidx=0;
		idx=0;
		N=n;
		pids=new ID[N];
		for (int i=0; i<N;i++)
			pids[i]=null;
	}
	
	
	public synchronized void discover ()
	{
		//System.out.println("Sending a Discovery Message");
        // look for any peer
        discoSvc.getRemoteAdvertisements(null, DiscoveryService.PEER,
                                          null, null, 2*N+1);
        
        
        
    }
	
	public synchronized void reset()
	{
		
		for (int i=0; i<N;i++)
			pids[i]=null;
		pidx=0;
		idx=0;	
		flush();
		
	}
	
	public void flush()
	{
		try {
	        Enumeration en = discoSvc.getLocalAdvertisements(DiscoveryService.PEER, null, null);
	        while (en.hasMoreElements()) {
	           discoSvc.flushAdvertisement( (Advertisement) en.nextElement());
	        }
	   } catch (IOException io) {
	       io.printStackTrace();
	   } 
	}
	
	public void republish()
	{
		Advertisement a;
		a=padv;
		long lifetime1,lifetime2;
		lifetime1=120000;
		lifetime2=0;
		try {discoSvc.publish(a,lifetime1,lifetime2);}
		catch(IOException ioe){System.out.println(ioe.toString());}
	}
	
	public boolean enoughPeers()
	{
		boolean r=false;
		if(pidx==N) r=true;
		return r;
	}
	
	public synchronized void discoveryEvent(DiscoveryEvent ev)
	{
		DiscoveryResponseMsg res = ev.getResponse();
        PeerAdvertisement peerAdv =null;
        //PeerGroupAdvertisement pgadv=null;
        Enumeration en = res.getAdvertisements();
        if (en != null ) {
            while (en.hasMoreElements()) {
                peerAdv = (PeerAdvertisement) en.nextElement();
                       
               if ((!(alreadyKnow(peerAdv.getPeerID())))&&(pidx<N))
            	{
            	 pids[pidx]=peerAdv.getPeerID();
            	 pidx++;
            	}      
            }
           }
   
	}
	
	
	public synchronized ID getID()
	{
	 ID id=null;
	  	
	 	if(pids[idx]!=null){id=pids[idx];idx++;}
	 	 	
	 return id;	
	}
	
	
	private boolean alreadyKnow(ID i)
	{
	 boolean r=false;
	 for (int j=0;j<N;j++)
	 {
	 	if((pids[j]!=null)&&(i.equals(pids[j])))
	 		{
	 		 r=true;
	 		 
	 		}
	 	if((pids[j]!=null)&&(i.equals(pg.getPeerID())))
	 		{
	 	 		 
	 		 r=true;
	 		}
	 }
	 return r;
	}
	
}