在线监听器实时人数统计如何实现？

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监听器在在线人数统计中的应用

javapackage com.fz.servlet;

import java.util.ArrayList;import java.util.List;import javax.servlet.annotation.WebListener;import javax.servlet.http.HttpSession;import javax.servlet.http.HttpSessionAttributeListener;

package com.fz.servlet; import java.util.ArrayList; import java.util.List; import javax.servlet.annotation.WebListener; import javax.servlet.http.HttpSession; import javax.servlet.http.HttpSessionAttributeListener; import javax.servlet.http.HttpSessionBindingEvent; import javax.servlet.http.HttpSessionEvent; import javax.servlet.http.HttpSessionListener; @WebListener public class Observers implements HttpSessionListener, HttpSessionAttributeListener{ //在线总人数 public static int count; //会员在线人数 public static List vipnums = new ArrayList<>(); @Override public void sessionCreated(HttpSessionEvent e) { count++; System.out.println("有人上线"); } @Override public void sessionDestroyed(HttpSessionEvent e) { count--; System.out.println("有人下线"); } @Override public void attributeAdded(HttpSessionBindingEvent e) { // session.setAttribute() 执行时 HttpSession session = e.getSession(); System.out.println(session);//session地址 System.out.println(session.getId());//session id System.out.println(e.getName());//session名 System.out.println(e.getValue());//session值 System.out.println(session.getAttribute(e.getName()));//session值 String nameString = (String) e.getValue(); vipnums.add(nameString); } @Override public void attributeRemoved(HttpSessionBindingEvent e) { // session.removeAttribute() 执行时 vipnums.remove(e.getValue().toString()); } @Override public void attributeReplaced(HttpSessionBindingEvent e) { // session.setAttribute() // session.setAttribute();第二次执行时（重新登录时执行） } }