Java在WEB中如何统计在线人数

  原理：   建立一个Session级别的Listener，然后在Session建立的时候往Application的一个向量变量List中写入用户信息，当Session释放时从变量List中删除该用户信息，就可以在Application的列表中得到在线用户列表了。

  

1. import javax.servlet.http.*; 
2. import javax.servlet.*; 
3. import java.util.*; 
5. public class onLineUser implements HttpSessionBindingListener { 
6.         private Vector users=new Vector();    
7.                
8.         public   int  getCount(){ 
9.                     users.trimToSize(); 
10.                     return  users.capacity(); 
11.         } 
12.         
13.           public  boolean existUser(String userName){ 
14.                     users.trimToSize(); 
15.                      boolean existUser= false ; 
16.                     for (int i=0;i 
17.                        { 
18.                                 if (userName.equals((String)users.get(i))) 
19.                                    { 
20.                                             existUser=true; 
21.                                             break ; 
22.                                        } 
23.                            } 
24.                         return existUser; 
25.             }     
27.             public  boolean deleteUser(String userName) { 
28.                     users.trimToSize(); 
29.                     if (existUser(userName)){ 
30.                                 int currUserIndex=-1; 
31.                                 for ( int  i=0;i 
32.                                         if(userName.equals((String)users.get(i))){ 
33.                                                 currUserIndex=i; 
34.                                                 break; 
35.                                             } 
36.                       } 
37.                     if  (currUserIndex!=-1){ 
38.                                 users.remove(currUserIndex); 
39.                                 users.trimToSize(); 
40.                     return true; 
41.                     } 
42.                 } 
43.                 return   false ; 
44.             } 
45.  
46.             public Vector getOnLineUser() 
47.             { 
48.                         return users; 
49.                 } 
50.     
51.                 public void valueBound(HttpSessionBindingEvent e) { 
52.                             users.trimToSize(); 
53.                             if(!existUser(e.getName())){ 
54.                                             users.add(e.getName()); 
55.                                             System.out.print(e.getName()+"/t 登入到系统/t"+(new Date())); 
56.                                             System. out .println( " 在线用户数为：" +getCount()); 
57.                             }else 
58.                                             System. out .println(e.getName()+ "已经存在" ); 
59.                             } 
60.  
61.                 public void valueUnbound(HttpSessionBindingEvent e) { 
62.                                     users.trimToSize(); 
63.                                         String userName=e.getName(); 
64.                                     deleteUser(userName); 
65.                                     System.out.print(userName+"/t 退出系统/t"+(new Date())); 
66.                                     System. out .println( " 在线用户数为：" +getCount()); 
67.                     } 
68. } 

 

 

1. JSP程序
2. jsp: 
3. <%@ page contentType="text/html;charset=gb2312" %> 
4. <%@ page import= "java.util.*"  %> 
5. "onlineuser" class="temp.jb.onLineUser" scope="application"/> 
6.  
7.  
8.  
9. "postMessage()"> 
10.  

11.  

    登陆成功，欢迎访问 

     
     
12.  
13. <% session = request.getSession(false); %> 
14. <% 
15. String username=request.getParameter("username"); 
16. if  (onlineuser.existUser(username)){ 
17. out.println("用户 "+username+" 已经登陆！"); 
18. } else { 
19. session.setMaxInactiveInterval(50); //Sesion有效时长，以秒为单位 
20. session.setAttribute(username,onlineuser); 
21. out.println("欢迎新用户: "+username+" 登陆到系统！"); 
22. } 
23. out.println(" 
    当前在线用户人数: "+onlineuser.getCount()+"  
    "); 
24. String ip = request.getRemoteAddr(); 
25. out.println(" 
    IP: "+ip+"  
    "); 
26. Vector vt=onlineuser.getOnLineUser(); 
27. Enumeration e = vt.elements(); 
28. out .println( "在线用户列表" ); 
29. out.println(" "); 
30. out .println( "  用户名  " ); 
31. while(e.hasMoreElements()){ 
32. out .println( "  " ); 
33. out.println((String)e.nextElement()+" 
    "); 
34. out .println( "  " ); 
35. } 
36. out .println( " " ); 
38. %> 
39.  

40.  

     
41. [ "javascript:window.close()">关闭窗口 ] 
42. <% 
43. out.println(" 

     +username+"'>退出系统  

    "); 
44. %> 
45.  
46.  
47.  
48.