IDEA 当前在线人数和历史访问量的示例代码
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 */@WebListenerpublic 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>rn' + '<html>rn' + '<head>rn' + '<meta charset='UTF-8'>rn' + '<title>登陆网页次数统计</title>rn' + '</head>rn' + '<body>'); out.print('<h1>'); out.print('您是第 '+ servletContext.getAttribute('count')+'位访客'); out.print('<h1>'); out.print('</body>rn' + '</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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