java统计在线人数

在web.xml文件中添加

<!-- 统计在线 监听 -->
<listener>
    <listener-class>com.connxun.config.listener.OnLineListener</listener-class>
</listener>

然后新增对应路径的监听文件

package com.connxun.config.listener;


import com.connxun.util.session.UserSession;

import javax.servlet.ServletContext;
import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;
import javax.servlet.http.HttpSessionAttributeListener;
import javax.servlet.http.HttpSessionBindingEvent;
import javax.servlet.http.HttpSessionEvent;
import javax.servlet.http.HttpSessionListener;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;

/**
 * 统计在线人数
 *
 * @author gaoyf
 */
public class OnLineListener implements ServletContextListener, HttpSessionListener, HttpSessionAttributeListener {

    // 声明一个ServletContext对象
    private ServletContext application = null;
    private static HashMap<String, UserSession> hashMap = new HashMap<String, UserSession>();

    public void contextInitialized(ServletContextEvent sce) {
        // 容器初始化时，向application中存放一个空的容器
        this.application = sce.getServletContext();
        this.application.setAttribute("allUser", new ArrayList<UserSession>());
    }


    public void contextDestroyed(ServletContextEvent sce) {
    }

    public void sessionCreated(HttpSessionEvent se) {
        UserSession userSession = (UserSession) se.getSession().getAttribute("userSession");
        if (userSession != null) {
            hashMap.put(se.getSession().getId(), userSession);
            System.out.println("用户登录，当前用户总数：" + hashMap.size());
        }
        System.out.println(se.getSession().getId());
    }

    public void sessionDestroyed(HttpSessionEvent se) {
        // 将用户名称从列表中删除
        List l = (List) this.application.getAttribute("allUser");
        UserSession userSession = (UserSession) se.getSession().getAttribute("userSession");
        if (userSession != null)
            l.remove(userSession);
        System.out.println("session过期，当前用户数：" + l.size());
        this.application.setAttribute("allUser", l);
        System.out.println(se.getSession().getId());
        if (hashMap.containsKey(se.getSession().getId())) {
            hashMap.remove(se.getSession().getId());
            System.out.println("session自动销毁：" + hashMap.size());
        }
    }

    public void attributeAdded(HttpSessionBindingEvent se) {
        // 如果登录成功，则将用户名保存在列表之中
        List<UserSession> l = (List<UserSession>) this.application.getAttribute("allUser");
        l.add((UserSession) se.getValue());
        this.application.setAttribute("allUser", l);
        hashMap.put(se.getSession().getId(), (UserSession) se.getValue());
        System.out.println(se.getSession().getId());
        System.out.println("系统登录，当前用户数：" + hashMap.size());

        UserSession userSession = (UserSession) se.getSession().getAttribute("userSession");
        if (userSession != null) {
            System.out.println(se.getSession().getId());
            hashMap.put(se.getSession().getId(), userSession);
            System.out.println("用户登录，当前用户总数：" + hashMap.size());
        }
    }

    public void attributeRemoved(HttpSessionBindingEvent se) {
        List<UserSession> l = (List<UserSession>) this.application.getAttribute("allUser");
        UserSession userSession = (UserSession) se.getValue();
        if (userSession != null)
            l.remove(userSession);
        System.out.println(se.getSession().getId());
        hashMap.remove(se.getSession().getId());
        System.out.println("用户注销，当前用户数：" + hashMap.size());
        this.application.setAttribute("allUser", l);
    }

    public void attributeReplaced(HttpSessionBindingEvent se) {
    }

}