【JavaEE企业应用实战学习记录】sessionListener

 1 package sanglp.servlet;
 2 
 3 
 4 import javax.servlet.ServletContext;
 5 import javax.servlet.annotation.WebListener;
 6 import javax.servlet.http.HttpSession;
 7 import javax.servlet.http.HttpSessionEvent;
 8 import java.util.Hashtable;
 9 import java.util.Map;
10 
11 /**
12  * Created by Administrator on 2016/10/6.
13  */
14 @WebListener
15 public class HttpSessionListener implements javax.servlet.http.HttpSessionListener {
16 
17     //当用户与服务之间开始session时触发该方法
18     @Override
19     public void sessionCreated(HttpSessionEvent httpSessionEvent) {
20         HttpSession session=httpSessionEvent.getSession();
21         ServletContext application=session.getServletContext();
22         //获取sessionId
23         String sessionId=session.getId();
24         //如果是一次新的会话
25         if(session.isNew()){
26             String user=(String)session.getAttribute("user");
27             //未登陆用户当游客处理
28             user=(user==null)?"游客":user;
29             Map<String,String> online=(Map<String, String>) application.getAttribute("online");
30             if(online==null){
31                 online=new Hashtable<String,String>();
32                 //将用户在线信息放入Map中
33                 online.put(sessionId,user);
34                 application.setAttribute("online",online);
35             }
36         }
37     }
38 
39     //当用户与服务器之间session断开时触发该方法
40     @Override
41     public void sessionDestroyed(HttpSessionEvent httpSessionEvent) {
42     HttpSession session=httpSessionEvent.getSession();
43         ServletContext application=session.getServletContext();
44         String sessionId=session.getId();
45         Map<String,String> online=(Map<String,String>)application.getAttribute("online");
46         if(online!=null){
47             //删除该用户的在线信息
48             online.remove(sessionId);
49         }
50         application.setAttribute("online",online);
51     }
52 }