napletserverlog.java

移动Agent编程工具Naplet

/*
 * @<#> NapletServerLog.java version 0.0.1, 1/1/2000
 *
 * THIS PROGRAM IS FREE SOFTWARE; YOU CAN DISTRIBUTE IT AND/OR
 * MODIFY IT UNDER THE TERMS OF THE GNU GENERAL PUBLIC LICENSE 
 * AS PUBLISHED BY THE FREE SOFTWARE FOUNDATION.
 *
 * THIS PROGRAM IS DISTRIBUTED IN THE HOPE THAT IT WILL BE USEFUL,
 * BUT WITHOUT ANY WARRANTY; WITHOUT EVEN THE IMPLIED WARRANTY OF
 * MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. SEE THE 
 * GNU GENERAL PUBLIC LICENSE FOR MORE DETAILS.
 *
 * Copyright (c) 2000-2002 Wayne State University. All Rights Reserved.
 */
package naplet.server;

import java.util.*;
import java.net.*;
import naplet.*;

/**
 * The <code>NapletServerLog</code> class implements a naplet table within
 * a server. The table contains a vector of <code>FootPrint</code>
 * for each visiting naplet. Each footprint records 
 *   where-come-from/where-leave-for, arrival/departure time, ARRIVAL/DEPART 
 * 
 * @see NapletServerImpl
 * @version 0.0.1, 1/1/2000
 * @author C. Xu
 */

public class NapletServerLog {

	private HashMap table; 

	public NapletServerLog() {
		table = new HashMap();
	}
	
	public synchronized void arrive( Naplet nap, InetAddress src) {
		try {
			register(nap.getNapletID(), new URN(src), new Date(), NapletEvent.ARRIVE);
		} catch (InvalidURNException iue) {
			throw new NapletInternalError( iue.getMessage() );
		}
	}

	public synchronized void depart( Naplet nap, URN dest ) {
		register(nap.getNapletID(), dest, new Date(), NapletEvent.DEPART);
	}

	/**
	 * Check the visiting log of a naplet; return an ArrayList of footprints
	 * @param nid Naplet in question 
	 */ 
	public synchronized ArrayList checkLog( NapletID nid) {
		ArrayList fpList = null;

		String key = nid.toString();
		if (table.containsKey(key)) {
			fpList = (ArrayList)table.get(key);
		}
		return fpList;
	}

	void register(NapletID nid, URN server, Date time, int event){
       	try { 
			String key = nid.toString();
			FootPrint fp = new FootPrint(server, time, event);
		
			/* Since a naplet may visit a server more than one time
		 	* footprints of the naplet are stored in an ArrayList
		 	*/
			if (table.containsKey(key)) {
				ArrayList footprints = (ArrayList) table.get(key);
				footprints.add(fp);
			} else {
				ArrayList footprints = new ArrayList();
				footprints.add(fp);
				table.put(key, footprints);
			}
		} catch (InvalidEventException iee) {
			throw new NapletInternalError( iee.getMessage() );
		}

	}
                 
}