运用HttpSessionListener统计在线人数

使用HttpSessionListener统计在线人数

1.新建一个类实现HttpSessionListener接口,并实现sessionCreated和sessionDestroyed方法

package cn.com.myblog.util;

import java.util.HashSet;

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

public class OnlineBodyCount implements HttpSessionListener {
	/**
	 * 新建session
	 */
	@SuppressWarnings("unchecked")
	@Override
	public void sessionCreated(HttpSessionEvent event) {
		HttpSession session=event.getSession();
		ServletContext application=session.getServletContext();
		 HashSet<HttpSession> sessions=(HashSet<HttpSession>)application.getAttribute("sessions");
		 if(sessions==null){
			 sessions=new HashSet<HttpSession>();
			 application.setAttribute("sessions",sessions);
		 }
		 sessions.add(session);
	}
	/**
	 * session销毁
	 */
	@SuppressWarnings("unchecked")
	@Override
	public void sessionDestroyed(HttpSessionEvent event) {
		HttpSession session=event.getSession();
		ServletContext application=session.getServletContext();
		 HashSet<HttpSession> sessions=(HashSet<HttpSession>)application.getAttribute("sessions");
		 sessions.remove(session);

	}
}

 

2.写一个方法获取application保存的对象

 

@SuppressWarnings("unchecked")
	public String online_body(){
		HttpServletRequest request=ServletActionContext.getRequest();
		ServletContext application=request.getSession().getServletContext();
		HashSet<HttpSession> sessions=(HashSet<HttpSession>)application.getAttribute("sessions");
		if(sessions!=null &&!sessions.isEmpty()){
			System.out.println(sessions.size());
		}
		return null;
	}