session的使用

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一、效果图

使用多个浏览器打开模拟多用户登录

二、相关代码

人数访问监听

package com.my.deal;

import javax.servlet.ServletContext;

import javax.servlet.http.HttpSession;

import javax.servlet.http.HttpSessionEvent;

import javax.servlet.http.HttpSessionListener;

 

public class ServletListener implements HttpSessionListener{

    /**

     * 创建

     */

    @Override

    public void sessionCreated(HttpSessionEvent se) {

        HttpSession session=se.getSession();

        ServletContext servletContext = session.getServletContext();

        Object object = servletContext.getAttribute("num");

            if (object == null) {

                servletContext.setAttribute("num", 1);

            } else {

                Object num = servletContext.getAttribute("num");

                int num1 = (int) num;

                servletContext.setAttribute("num", num1 + 1);

            }

          

    }

    /**

     * 销毁

     */

    @Override

    public void sessionDestroyed(HttpSessionEvent se) {

        ServletContext servletContext = se.getSession().getServletContext();

        servletContext.setAttribute("num", (long)servletContext.getAttribute("num")-1);

    }

 

}

在web.xml中注册监听器

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"
version="4.0">
<listener>
<listener-class>ServletListener</listener-class>
</listener>
</web-app>