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>
