meeting.java

aglet的部分源码

package com.ibm.agletx.patterns;

/*
 * @(#)Meeting.java
 * 
 * IBM Confidential-Restricted
 * 
 * OCO Source Materials
 * 
 * 03L7246 (c) Copyright IBM Corp. 1996, 1998
 * 
 * The source code for this program is not published or otherwise
 * divested of its trade secrets, irrespective of what has been
 * deposited with the U.S. Copyright Office.
 */

import com.ibm.aglet.*;
import java.net.*;
import java.io.*;
import java.util.*;

/**
 * This <tt>Meeting</tt> class abstracts light synchronization between
 * multiple aglets by using a meeting concept. A meeting is established by
 * creating a meeting object and distribute it among the aglets which
 * suppose to participate in the meeting.
 * A meeting object includes:
 * <br> 1. the meeting place (URL)
 * <br> 2. a meeting identifier
 * <br> 3. an optional list of agletIDs, named <tt>colleagues</tt>, of aglets
 * which are expected to be presented at the meeting place
 * <br> 4. an optional object (named <tt>attachedInfo</tt>) describing
 * additional information regarding the meeting (e.g. list or number of
 * participants, minimum number of required participants).
 * <br> <br>
 * Upon arrival to the meeting, an aglet notifies its arrival via
 * the <tt>ready</tt> method. As a result all aglets already presented
 * are notified of its arrival by receiving a special message
 * (its kind is that of the meeting ID)  with the agletID of this newly
 * arrived aglet.
 * 
 * @version     1.0    96/12/28
 * @author      Yariv Aridor
 */

public final class Meeting implements java.io.Serializable {

	private String _id = null;
	private String _place = null;
	private Vector _colleagues = null;
	private Object _info = null;

	/**
	 * A Constructor
	 * @param place the meeting place.
	 */
	public Meeting(String place) {
		_place = place;
		_id = "meet." + String.valueOf(Math.random());
	}
	/**
	 * A Constructor
	 * @param place the meeting place.
	 * @param colleagues the colleagues
	 * @exception AgletException if colleagues is invalid (should include only AgletID objects)
	 */

	public Meeting(String place, Vector colleagues) throws AgletException {
		_place = place;
		_id = "meet." + String.valueOf(Math.random());
		setColleagues(colleagues);
	}
	private Vector append(Vector v1, Vector v2) {
		Vector v = new Vector();

		if (v1 == null) {
			return v2;
		} 
		if (v2 == null) {
			return v1;

		} 
		for (int i = 0; i < v1.size(); i++) {
			v.addElement(v1.elementAt(i));
		} 
		for (int j = 0; j < v2.size(); j++) {
			v.addElement(v2.elementAt(j));
		} 
		return v;
	}
	private void checkColleagues(Vector c) throws AgletException {
		for (int i = 0; i < c.size(); i++) {
			if ((c.elementAt(i) instanceof AgletID) == false) {
				throw new AgletException("non AgletIdentifer object is included");
			} 
		} 
	}
	private void checkColleaguesArePresent(AgletContext ctx, 
										   Vector c) throws AgletException {
		boolean found = false;

		if (c == null) {
			return;
		} 
		for (int i = 0; i < c.size(); i++) {
			found = false;
			for (Enumeration e = ctx.getAgletProxies(); 
					e.hasMoreElements(); ) {
				AgletProxy p = (AgletProxy)e.nextElement();

				if (p.getAgletID().equals(c.elementAt(i))) {
					found = true;
					break;
				} 
			} 
			if (found == false) {
				throw new AgletException("not all colleagues are presented");
			} 
		} 
	}
	public Object getAttachedInfo() {
		return _info;
	}
	// temporaty function to overcome adding a trial "/" while
	// converting from a string to a URL.
	private URL getHostingURL(AgletContext ctx) {
		try {
			return new URL(ctx.getHostingURL().toString());
		} catch (IOException e) {
			return null;
		} 
	}
	public String getID() {
		return _id;
	}
	public String getPlace() {
		return _place;
	}
	/**
	 * Accepts an aglet to a meeting.
	 * @param aglet the arrived aglet.
	 * @return enumeration of the agletID of all presented aglets.
	 * @exception AgletException if wrong meeting place or if any
	 * of the colleagues is not presented.
	 */
	public Enumeration ready(Aglet ag) throws AgletException {

		// get aglet identifier
		AgletID aid = ag.getAgletID();
		AgletContext ctx = ag.getAgletContext();

		URL url = null;

		try {
			url = new URL(_place);
		} catch (Exception ex) {}

		if (!NetUtils.sameURL(url, getHostingURL(ctx))) {
			throw new AgletException("a wrong meeting place : " + _place);
		} else {
			checkColleaguesArePresent(ctx, _colleagues);
			return append(ready0(aid, ctx, _id, ag), _colleagues).elements();
		} 
	}
	private synchronized static Vector ready0(AgletID aid, AgletContext ctx, 
											  String id, 
											  Aglet ag) throws AgletException {

		ReplySet rs = ctx.multicastMessage(new Message(id, aid));

		ag.subscribeMessage(id);
		return toVector(rs);
	}
	public void setAttachedInfo(Object obj) {
		_info = obj;
	}
	public void setColleagues(Vector colleagues) throws AgletException {
		checkColleagues(colleagues);
		_colleagues = colleagues;
	}
	public void setID(String id) {
		_id = "meet." + id;
	}
	private static Vector toVector(ReplySet rs) throws AgletException {
		Vector v = new Vector();

		try {
			while (rs.hasMoreFutureReplies()) {
				Object obj = rs.getNextFutureReply().getReply();

				if (obj instanceof AgletID) {
					v.addElement(obj);
				} else {
					throw new AgletException("a non AgletIdentifer object");
				} 
			} 
		} catch (Exception e) {}
		return v;
	}
}