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IDEA 當(dāng)前在線人數(shù)和歷史訪問(wèn)量的示例代碼

更新時(shí)間：2020年08月07日 14:18:51 作者：柴大大

這篇文章主要介紹了IDEA 當(dāng)前在線人數(shù)和歷史訪問(wèn)量的實(shí)例代碼，本文給大家介紹的非常詳細(xì)，對(duì)大家的學(xué)習(xí)或工作具有一定的參考借鑒價(jià)值,需要的朋友可以參考下

當(dāng)前在線人數(shù)

一共需要三處

創(chuàng)建監(jiān)聽(tīng)器

package com.count;
import javax.servlet.ServletContext;
import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;
import javax.servlet.annotation.WebListener;
/*
 初始化:
   只有服務(wù)器的啟動(dòng)，才會(huì)創(chuàng)建servletContext對(duì)象。
  用于監(jiān)聽(tīng)servletContext創(chuàng)建，一旦創(chuàng)建servletContext創(chuàng)建，則設(shè)置servletContext中的count值為0;
*/
@WebListener
/*
 這個(gè)注解的作用是啟動(dòng)監(jiān)聽(tīng)，相當(dāng)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) {
  //獲取ServletContext域?qū)ο?
  ServletContext servletContext = servletContextEvent.getServletContext();
  //給ServletContext域?qū)ο?，設(shè)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;
 
/**
 * @監(jiān)聽(tīng)在線人數(shù)，監(jiān)聽(tīng)session的創(chuàng)建和銷毀
 *  如果session創(chuàng)建 獲取ServletContext中的count++,重新設(shè)置
 *  如果session銷毀 獲取ServletContext中的count--,重新設(shè)置
 */
@WebListener
public class OnlineNumberHttpSessionListener implements HttpSessionListener {
 @Override
 public void sessionCreated(HttpSessionEvent httpSessionEvent) {
  //1.獲取session
  HttpSession session = httpSessionEvent.getSession();
  ServletContext servletContext = session.getServletContext();
  //2.獲取counnt值，加1
  int count = (int) servletContext.getAttribute("count");
  count++;
  //3.把servlet存儲(chǔ)到servletContext對(duì)象中
  servletContext.setAttribute("count",count);
 }
 
 @Override
 public void sessionDestroyed(HttpSessionEvent httpSessionEvent) {
 
  //1.獲取session
  HttpSession session = httpSessionEvent.getSession();
  ServletContext servletContext = session.getServletContext();
  //2.獲取counnt值，減1
  int count = (int) servletContext.getAttribute("count");
  count++;
  //3.把servlet存儲(chǔ)到servletContext對(duì)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>當(dāng)前在線人數(shù)：${count}</h1>
</body>
</html>

歷史訪問(wèn)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 {
  //設(shè)置字符編碼
  request.setCharacterEncoding("utf-8");
  response.setCharacterEncoding("utf-8");
  response.setContentType("text/html; charset=utf-8");
 
 
 
  //獲取全局的共享數(shù)據(jù)
  ServletContext servletContext = this.getServletContext();
 
  //獲取計(jì)數(shù)器count
  Integer count = (Integer) servletContext.getAttribute("count");
 
  //如果獲取的計(jì)算器對(duì)象為空 ，說(shuō)明是第一次訪問(wèn)，并將count，放入servletCount
  if( servletContext.getAttribute("count") == null) {
   count = 1;
   servletContext.setAttribute("count", count);
  }else {
   //否則就不是第一次訪問(wèn)，將登陸的計(jì)數(shù)器進(jìn)行加1的數(shù)據(jù)更新
   servletContext.setAttribute("count", count+1);
  }
 
  //將登陸的次數(shù)顯示在頁(yè)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>登陸網(wǎng)頁(yè)次數(shù)統(tǒng)計(jì)</title>\r\n" +
    "</head>\r\n" +
    "<body>");
  out.print("<h1>");
  out.print("您是第 "+ servletContext.getAttribute("count")+"位訪客");
  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>
 <%
 //統(tǒng)計(jì)網(wǎng)頁(yè)訪問(wèn)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對(duì)象讀取count參數(shù)的值，再在原值基礎(chǔ)上累加1
 application.setAttribute("count", count + 1);//application.setAttribute("count", new Integer(count.intValue() + 1));
 %>
 <h2>
 <!-- 輸出累加后的count參數(shù)對(duì)應(yīng)的值 -->
 歡迎您訪問(wèn)，本頁(yè)面已經(jīng)被訪問(wèn)過(guò) <font color="#ff0000"><%=application.getAttribute("count")%></font>次
 </h2>
 </body>
</html>

總結(jié)

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