DWR Server Push(服务器推技术) B/S即时通讯

package com.lhq;

import java.util.ArrayList;
import java.util.Collection;
import java.util.HashSet;
import java.util.List;

import javax.servlet.ServletContext;
import javax.servlet.http.HttpServletRequest;

import org.directwebremoting.ScriptSession;
import org.directwebremoting.ServerContext;
import org.directwebremoting.ServerContextFactory;
import org.directwebremoting.WebContextFactory;
import org.directwebremoting.proxy.dwr.Util;

/**
 * 处理聊天相关
 * 
 * @author 
 * 
 */
public class ChatManager {

	/** 保存当前在线用户列表 */
	public static List<User> users = new ArrayList<User>();

	/**
	 * 更新在线用户列表
	 * @param username 待添加到列表的用户名
	 * @param flag 是添加用户到列表,还是只获得当前列表
	 * @param request
	 * @return 用户userid
	 */
	public String updateUsersList(String username, boolean flag, HttpServletRequest request) {
		User user = null;
		if (flag) {	
			// 这里取会话(HttpSession)的id为用户id 
			user = new User(request.getSession().getId(), username);
			//保存用户到列表
			users.add(user);	
			//将用户id和页面脚本session绑定
			this.setScriptSessionFlag(user.getUserid());
		}
		//获得DWR上下文
		ServletContext sc = request.getSession().getServletContext();
		ServerContext sctx = ServerContextFactory.get(sc);
		//获得当前浏览 index.jsp 页面的所有脚本session
		Collection sessions = sctx.getScriptSessionsByPage("/chat/index.jsp");
		Util util = new Util(sessions);
		//处理这些页面中的一些元素
		util.removeAllOptions("users");
		util.addOptions("users", users, "username");
		util.removeAllOptions("receiver");
		util.addOptions("receiver", users,"userid","username");
		if(!flag){
			return null;
		}
		return user.getUserid();
	}

	/**
	 * 将用户id和页面脚本session绑定
	 * @param userid
	 */
	public void setScriptSessionFlag(String userid) {
		WebContextFactory.get().getScriptSession().setAttribute("userid", userid);
	}

	/**
	 * 根据用户id获得指定用户的页面脚本session
	 * @param userid
	 * @param request
	 * @return
	 */
	@SuppressWarnings("unchecked")
	public ScriptSession getScriptSession(String userid, HttpServletRequest request) {
		ScriptSession scriptSessions = null;
		Collection<ScriptSession> sessions = new HashSet<ScriptSession>();
		sessions.addAll(ServerContextFactory.get(request.getSession().getServletContext())
				.getScriptSessionsByPage("/chat/index.jsp"));
		for (ScriptSession session : sessions) {
			String xuserid = (String) session.getAttribute("userid");
			if (xuserid != null && xuserid.equals(userid)) {
				scriptSessions = session;
			}
		}
		return scriptSessions;
	}
	
	/**
	 * 发送消息
	 * @param sender 发送者
	 * @param receiverid 接收者id
	 * @param msg 消息内容
	 * @param request
	 */
	public void send(String sender,String receiverid,String msg,HttpServletRequest request){
		ScriptSession session = this.getScriptSession(receiverid, request);
		Util util = new Util(session);
		util.setStyle("showMessage", "display", "");
		util.setValue("sender", sender);
		util.setValue("msg", msg);
	}
}