如果对监听器不了解的话，可以参看下面这个CSDN
/qq_41901915/article/details/86477771
第一个文件，用来监听项目的开始，一旦这个项目开启了，那么我就初始化一个参数，count1，把它存到域中
package tools;import javax.servlet.ServletContext;import javax.servlet.ServletContextEvent;import javax.servlet.ServletContextListener;import javax.servlet.annotation.WebListener;@WebListenerpublic class Mycontextlistener implements ServletContextListener{@Overridepublic void contextDestroyed(ServletContextEvent sce) {// TODO Auto-generated method stub}@Overridepublic void contextInitialized(ServletContextEvent sce) {// TODO Auto-generated method stubServletContext c=sce.getServletContext();c.setAttribute("count1", 0);System.out.println("项目在线访问人数初始化完成");}}
第二个文件，一旦访问的话我就获取那个域对象，让它的数量+1，关掉的话就让它-1
package tools;import javax.servlet.ServletContext;import javax.servlet.annotation.WebListener;import javax.servlet.http.HttpSession;import javax.servlet.http.HttpSessionEvent;import javax.servlet.http.HttpSessionListener;@WebListenerpublic class Myhttpsessionlistener implements HttpSessionListener{public void sessionCreated(HttpSessionEvent se) {// TODO Auto-generated method stubHttpSession session=se.getSession();ServletContext c=session.getServletContext();int count=(int) c.getAttribute("count1");count++;c.setAttribute("count1", count);System.out.println("增加1");}public void sessionDestroyed(HttpSessionEvent se) {// TODO Auto-generated method stubHttpSession session=se.getSession();ServletContext c=session.getServletContext();int count=(int) c.getAttribute("count1");count--;c.setAttribute("count1", count);System.out.println("减少1");}}
第三个文件，然后再jsp页面进行显示
<%@ page language="java" contentType="text/html; charset=UTF-8"pageEncoding="UTF-8"%><!DOCTYPE html><html><head><meta charset="UTF-8"><title>Insert title here</title></head><body><h3>当前在线人数为：${ applicationScope.count1 }</h3></body></html>
