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IDEA 当前在线人数和历史访问量的示例代码

 更新时间：2020年8月7日 18:22  点击：2080

当前在线人数

一共需要三处

创建监听器

package com.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) {
 
 }
}

package com.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);
 }
}

修改index.jsp

<%@ 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>

历史访问量

import java.io.IOException;
import java.io.PrintWriter;
 
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
 
/**
 * Servlet implementation class countServlet1
 */
@WebServlet("/countServlet1")
public class countServlet1 extends HttpServlet {
 private static final long serialVersionUID = 1L;
 
 /**
  * @see HttpServlet#HttpServlet()
  */
 public countServlet1() {
  super();
  // TODO Auto-generated constructor stub
 }
 
 /**
  * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
  */
 protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
  //设置字符编码
  request.setCharacterEncoding("utf-8");
  response.setCharacterEncoding("utf-8");
  response.setContentType("text/html; charset=utf-8");
 
 
 
  //获取全局的共享数据
  ServletContext servletContext = this.getServletContext();
 
  //获取计数器count
  Integer count = (Integer) servletContext.getAttribute("count");
 
  //如果获取的计算器对象为空 ，说明是第一次访问，并将count，放入servletCount
  if( servletContext.getAttribute("count") == null) {
   count = 1;
   servletContext.setAttribute("count", count);
  }else {
   //否则就不是第一次访问，将登陆的计数器进行加1的数据更新
   servletContext.setAttribute("count", count+1);
  }
 
  //将登陆的次数显示在页面上
  PrintWriter out =response.getWriter();
  out.print("<!DOCTYPE html>\r\n" +
    "<html>\r\n" +
    "<head>\r\n" +
    "<meta charset=\"UTF-8\">\r\n" +
    "<title>登陆网页次数统计</title>\r\n" +
    "</head>\r\n" +
    "<body>");
  out.print("<h1>");
  out.print("您是第 "+ servletContext.getAttribute("count")+"位访客");
  out.print("<h1>");
  out.print("</body>\r\n" +
    "</html>");
 }
 
 /**
  * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
  */
 protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
  // TODO Auto-generated method stub
  doGet(request, response);
 }
 
}

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
 <head>
 <title>$Title$</title>
 </head>
 <body>
 <%
 //统计网页访问量
 if (application.getAttribute("count") == null) {
  application.setAttribute("count", 0);//application.setAttribute("count", new Integer(0));
 }
 Integer count = (Integer) application.getAttribute("count");
 //使用application对象读取count参数的值，再在原值基础上累加1
 application.setAttribute("count", count + 1);//application.setAttribute("count", new Integer(count.intValue() + 1));
 %>
 <h2>
 <!-- 输出累加后的count参数对应的值 -->
 欢迎您访问，本页面已经被访问过 <font color="#ff0000"><%=application.getAttribute("count")%></font>次
 </h2>
 </body>
</html>

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