[转]jsp统计在线人数和在线注册人数

一、统计在线人数
1.监听器

package com.logcd.listener;

 import javax.servlet.ServletContext;
 import javax.servlet.http.HttpSessionEvent;
 import javax.servlet.http.HttpSessionListener;

 public class SessionCounter implements HttpSessionListener {
     public void sessionCreated(HttpSessionEvent event) {
        ServletContext ctx = event.getSession( ).getServletContext( );
         Integer numSessions = (Integer) ctx.getAttribute("numSessions");
         if (numSessions == null) {
             numSessions = new Integer(1);
         }else {
             int count = numSessions.intValue( );
             numSessions = new Integer(count + 1);
        }
         ctx.setAttribute("numSessions", numSessions);
    }
     public void sessionDestroyed(HttpSessionEvent event) {
        ServletContext ctx = event.getSession( ).getServletContext( );
         Integer numSessions = (Integer) ctx.getAttribute("numSessions");
         if (numSessions == null) {
             numSessions = new Integer(0);
        }
         else {
             int count = numSessions.intValue( );
             numSessions = new Integer(count - 1);
        }
         ctx.setAttribute("numSessions", numSessions);
    }
}

package com.logcd.listener;

import javax.servlet.ServletContext; 
import javax.servlet.http.HttpSessionEvent; 
import javax.servlet.http.HttpSessionListener; 

public class SessionCounter implements HttpSessionListener { 
    public void sessionCreated(HttpSessionEvent event) { 
        ServletContext ctx = event.getSession( ).getServletContext( ); 
        Integer numSessions = (Integer) ctx.getAttribute("numSessions"); 
        if (numSessions == null) { 
            numSessions = new Integer(1); 
        }else { 
            int count = numSessions.intValue( ); 
            numSessions = new Integer(count + 1); 
        } 
        ctx.setAttribute("numSessions", numSessions); 
    } 
    public void sessionDestroyed(HttpSessionEvent event) { 
        ServletContext ctx = event.getSession( ).getServletContext( ); 
        Integer numSessions = (Integer) ctx.getAttribute("numSessions"); 
        if (numSessions == null) { 
            numSessions = new Integer(0); 
        } 
        else { 
            int count = numSessions.intValue( ); 
            numSessions = new Integer(count - 1); 
        } 
        ctx.setAttribute("numSessions", numSessions); 
    } 
} 

说明：实现了HttpSessionListener定义的两个方法：sessionCreated()和sessionDestroyed()。这两个方法可以监听到当前应用中session的创建和销毁情况。
以下两种情况下就会发生sessionDestoryed（会话销毁）事件：
(1)执行session.invalidate()方法时。
(2)如果用户长时间没有访问服务器，超过了会话最大超时时间，服务器就会自动销毁超时的session。

<session-config>
     <session-timeout>1</session-timeout>
 </session-config>

<session-config>
    <session-timeout>1</session-timeout>
</session-config>

时间单位是一分钟，并且只能是整数，如果是零或负数，那么会话就永远不会超时。
2.web.xml中配置

<listener>
      <listener-class>com.logcd.listener.SessionCounter</listener-class>
 </listener>

	<listener> 
      <listener-class>com.logcd.listener.SessionCounter</listener-class> 
	</listener> 

3.jsp调用

目前共有<span class="salient"> <%=application.getAttribute("numSessions")%> </span>人在线

							目前共有<span class="salient"> <%=application.getAttribute("numSessions")%> </span>人在线

二、统计注册人数
1.监听器

package com.logcd.listener;

 import java.util.HashMap;
 import java.util.Map;

 import javax.servlet.ServletContext;
 import javax.servlet.http.HttpSession;
 import javax.servlet.http.HttpSessionBindingEvent;
 import javax.servlet.http.HttpSessionBindingListener;

 public class OnlineUserBindingListener implements HttpSessionBindingListener{

     private String userId;
     private String userName;

     public OnlineUserBindingListener(String userId,String username){
         this.setUserId(userId);
         this.setUserName(userName);
    }

     @SuppressWarnings("unchecked")
     public void valueBound(HttpSessionBindingEvent event) {
        HttpSession session = event.getSession();
        ServletContext application = session.getServletContext();

         // 把用户放入在线列表
         Map onlineUserList = (Map) application.getAttribute("onlineUserList");
         // 第一次使用前，需要初始化
         if (onlineUserList == null) {
             onlineUserList = new HashMap();
             application.setAttribute("onlineUserList", onlineUserList);
        }
         onlineUserList.put(this.userId, this.userName);

    }

     public void valueUnbound(HttpSessionBindingEvent event) {
        HttpSession session = event.getSession();
        ServletContext application = session.getServletContext();

         // 从在线列表中删除用户
         Map onlineUserList = (Map) application.getAttribute("onlineUserList");
         onlineUserList.remove(this.userId);

    }


     public String getUserId() {
         return userId;
    }

     public void setUserId(String userId) {
         this.userId = userId;
    }

     public String getUserName() {
         return userName;
    }

     public void setUserName(String userName) {
         this.userName = userName;
    }

}

package com.logcd.listener;

import java.util.HashMap;
import java.util.Map;

import javax.servlet.ServletContext;
import javax.servlet.http.HttpSession;
import javax.servlet.http.HttpSessionBindingEvent;
import javax.servlet.http.HttpSessionBindingListener;

public class OnlineUserBindingListener implements HttpSessionBindingListener{

	private String userId;
	private String userName;
	
	public OnlineUserBindingListener(String userId,String username){
		this.setUserId(userId);
		this.setUserName(userName);
	}
	
	@SuppressWarnings("unchecked")
	public void valueBound(HttpSessionBindingEvent event) {
		HttpSession session = event.getSession();
	    ServletContext application = session.getServletContext();

	    // 把用户放入在线列表
	    Map onlineUserList = (Map) application.getAttribute("onlineUserList");
	    // 第一次使用前，需要初始化
	    if (onlineUserList == null) {
	        onlineUserList = new HashMap();
	        application.setAttribute("onlineUserList", onlineUserList);
	    }
	    onlineUserList.put(this.userId, this.userName);
		
	}

	public void valueUnbound(HttpSessionBindingEvent event) {
		HttpSession session = event.getSession();
	    ServletContext application = session.getServletContext();

	    // 从在线列表中删除用户
	    Map onlineUserList = (Map) application.getAttribute("onlineUserList");
	    onlineUserList.remove(this.userId);
		
	}


	public String getUserId() {
		return userId;
	}

	public void setUserId(String userId) {
		this.userId = userId;
	}

	public String getUserName() {
		return userName;
	}

	public void setUserName(String userName) {
		this.userName = userName;
	}

}

说明：实现了HttpSessionBindingListener接口，接口中共定义了两个方法：valueBound()和valueUnbound()，分别对应数据绑定，和取消绑定两个事件。
所谓对session进行数据绑定，就是调用session.setAttribute()把HttpSessionBindingListener保存进session中。
HttpSessionListener只需要设置到web.xml中就可以监听整个应用中的所有session。HttpSessionBindingListener必须实例化后放入某一个session中，才可以进行监听。

从监听范围上比较，HttpSessionListener设置一次就可以监听所有session，HttpSessionBindingListener通常都是一对一的。

valueUnbound的触发条件是以下三种情况：
(1)执行session.invalidate()时。
(2)session超时，自动销毁时。
(3)执行session.setAttribute("onlineUserListener", "其他对象");或session.removeAttribute("onlineUserListener");将listener从session中删除时。
因此，只要不将listener从session中删除，就可以监听到session的销毁。

2.jsp调用
(1)login.jsp

<%@ page language="java" import="java.util.*" pageEncoding="gbk"%>
 <%@ page import="com.logcd.listener.OnlineUserBindingListener"%>
<%
    String path = request.getContextPath();
     String basePath = request.getScheme() + "://"
             + request.getServerName() + ":" + request.getServerPort()
             + path + "/";
     String userId = "2000090603";
     String userName = "LogCN";
    session.setAttribute(userId,userName);
     session.setAttribute("onlineUserBindingListener", new OnlineUserBindingListener(userId,userName));
     response.sendRedirect("counter.jsp");
%>

<%@ page language="java" import="java.util.*" pageEncoding="gbk"%>
<%@ page import="com.logcd.listener.OnlineUserBindingListener"%>
<%
	String path = request.getContextPath();
	String basePath = request.getScheme() + "://"
			+ request.getServerName() + ":" + request.getServerPort()
			+ path + "/";
	String userId = "2000090603";
	String userName = "LogCN";
	session.setAttribute(userId,userName);
	session.setAttribute("onlineUserBindingListener", new OnlineUserBindingListener(userId,userName));
	response.sendRedirect("counter.jsp");
%>

(2)counter.jsp

<%@ page language="java" import="java.util.*" pageEncoding="gbk"%>
 注册用户<span class="salient"><%=((Map)application.getAttribute("onlineUserList")).size()%> </span> 人