使用Servlet监听器统计在线用户人数

实现HttpSessionListener接口 

package org.fool.simpleservlet.listener;

import javax.servlet.annotation.WebListener;
import javax.servlet.http.HttpSessionEvent;
import javax.servlet.http.HttpSessionListener;

@WebListener
public class OnlineUserListener implements HttpSessionListener {

	private static int userCount = 0;

	public void sessionCreated(HttpSessionEvent event) {
		userCount++;
		event.getSession().getServletContext()
				.setAttribute("userCount", userCount);
	}

	public void sessionDestroyed(HttpSessionEvent event) {
		userCount--;
		event.getSession().getServletContext()
				.setAttribute("userCount", userCount);
	}

}

 

在jsp页面中显示监听的在线统计人数结果，使用el表达式

Online User Count : ${applicationScope.userCount}

 

为了便于测试，在web.xml设置session的超时时间为1min

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