Users Online website statistics

Copyright: Attribution, allow others to create paper-based, and must distribute paper (based on the original license agreement with the same license Creative Commons )

problem:

How to own a website user statistics (where users include tourist) numbers online?

analysis:

First of all, I met a problem like the idea at first analysis.

What technology can monitor user access to the server? ( Listeners )
Use those techniques, real-time storage server every time the number of users landing? (Java four domain object)
Those with technology that allows users to display the number of pages to the client? (El expression)

If I raise the above knowledge, you are not very understanding, it is recommended to learn at their own Baidu. I only had a relatively small demo, a train of thought.

In the code, there is a very clear presentation.

core content:

The directory structure of the project are as follows:

First create a javaweb project, clear project structure in the figure. (1 represents the project name, 3.jar package basic package (el expressions official website to download it), this is a .jar package Download ( https://download.csdn.net/download/longyanchen/ 11,250,452 )), precautions need to build the project on their own server, deploy the project directly to the server on it. Project preparation environment, I will not describe. (In order to prevent some brothers, put the bag in the wrong direction, I will go all pass)

InitServletContexListener.java(服务器初始化)：


package com.cyl.count;

import javax.servlet.ServletContext;
import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;
import javax.servlet.annotation.WebListener;
/*
    初始化:
         只有服务器的启动，才会创建servletContext对象。
        用于监听servletContext创建，一旦创建servletContext创建，则设置servletContext中的count值为0;
*/
@WebListener
/*
    这个注解的作用是启动监听，相当于在web.xml配置（
    <listener>
        <listener-class>com.cyl.count.InitServletContexListener</listener-class>
    </listener>
*/
public class InitServletContexListener implements ServletContextListener {
    @Override
    public void contextInitialized(ServletContextEvent servletContextEvent) {
        //获取ServletContext域对象
        ServletContext servletContext = servletContextEvent.getServletContext();
        //给ServletContext域对象，设置count=0
        servletContext.setAttribute("count",0);
    }

    @Override
    public void contextDestroyed(ServletContextEvent servletContextEvent) {

    }
}

OnlineNumberHttpSessionListener.java（用户现在监听）：


package com.cyl.count;

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

/**
 * @监听在线人数，监听session的创建和销毁
 *     如果session创建 获取ServletContext中的count++,重新设置
 *     如果session销毁 获取ServletContext中的count--,重新设置
 */
@WebListener
public class OnlineNumberHttpSessionListener implements HttpSessionListener {
    @Override
    public void sessionCreated(HttpSessionEvent httpSessionEvent) {
        //1.获取session
        HttpSession session = httpSessionEvent.getSession();
        ServletContext servletContext = session.getServletContext();
        //2.获取counnt值，加1
        int count = (int) servletContext.getAttribute("count");
        count++;
        //3.把servlet存储到servletContext对象中
        servletContext.setAttribute("count",count);
    }

    @Override
    public void sessionDestroyed(HttpSessionEvent httpSessionEvent) {

        //1.获取session
        HttpSession session = httpSessionEvent.getSession();
        ServletContext servletContext = session.getServletContext();
        //2.获取counnt值，减1
        int count = (int) servletContext.getAttribute("count");
        count++;
        //3.把servlet存储到servletContext对象中
        servletContext.setAttribute("count",count);
    }
}

the index.jsp (display the number of users):


<%--
  Created by IntelliJ IDEA.
  User: cyl
  Date: 2019/6/19 0019
  Time: 21:51
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<%@taglib prefix="c" uri="http://java.sun.com/jstl/core" %>
<html>
  <head>
    <title>$Title$</title>
  </head>
  <body>
      <h1>当前在线人数：${count}</h1>
  </body>
</html>