J2EE HttpSessionAttributeListener实现登录用户在线记录

web.xml配置

 <listener><listener-class>com.interceptor.UserListener1</listener-class></listener>

代码，实现HttpSessionAttributeListener接口，在httpsession中添加/移除用户信息时实现登录人数统计

package com.interceptor;

import javax.servlet.http.HttpSessionActivationListener;
import javax.servlet.http.HttpSessionAttributeListener;
import javax.servlet.http.HttpSessionBindingEvent;
import javax.servlet.http.HttpSessionEvent;
import javax.servlet.http.HttpSessionListener;


public class UserListener1 implements HttpSessionListener,HttpSessionActivationListener,HttpSessionAttributeListener {
	
	private static int acivateusercount=0;

	@Override
	public void sessionCreated(HttpSessionEvent arg0) {
		// TODO Auto-generated method stub		
		
	}

	@Override
	public void sessionDestroyed(HttpSessionEvent arg0) {
		// TODO Auto-generated method stub
		
	}
	
	public  static synchronized int getactivated (){
		
		return acivateusercount;
		
	}

	@Override
	public void sessionDidActivate(HttpSessionEvent arg0) {
		// TODO Auto-generated method stub	}

	@Override
	public void sessionWillPassivate(HttpSessionEvent arg0) {
		// TODO Auto-generated method stub
	}

	@Override
	public void attributeAdded(HttpSessionBindingEvent arg0) {
		// TODO Auto-generated method stub
	//	acivateusercount++;
		Object ob = arg0.getName();
		if(ob!=null && "user".equals(ob.toString())){
			acivateusercount++;
			System.out.println("attributeAdded user: "+ ((User)arg0.getValue()).getUserId());
			System.out.println("online count: " + getactivated() );
		}
	//	
	}

	@Override
	public void attributeRemoved(HttpSessionBindingEvent arg0) {
		// TODO Auto-generated method stub
		Object ob = arg0.getName();
		if(ob!=null && "user".equals(ob.toString())){
			if(acivateusercount>0)acivateusercount--;
			System.out.println("attributeRemoved user: "+ ((User

)arg0.getValue()).getUserId());System.out.println("online count: " + getactivated() );}}@Overridepublic void attributeReplaced(HttpSessionBindingEvent arg0) {// TODO Auto-generated method stub}}