监听器
package cn.itcast.web.listener;
import java.util.LinkedHashMap;
import java.util.Map;
import javax.servlet.ServletContext;
import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;
public class AListener implements ServletContextListener {
/**
* 在服务器启动时创建Map，保存到ServletContext
*/
public void contextInitialized(ServletContextEvent sce) {
// 创建Map
Map<String,Integer> map = new LinkedHashMap<String,Integer>();
// 得到ServletContext
ServletContext application = sce.getServletContext();
// 把map保存到application中
application.setAttribute("map", map);
}
public void contextDestroyed(ServletContextEvent sce) {
}
}
过滤器
package cn.itcast.web.filter;
import java.io.IOException;
import java.util.Map;
import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
/**
* 从application中获取Map
* 从request中得到当前客户端的IP
* 进行统计工作，结果保存到Map中
* @author cxf
*
*/
public class AFilter implements Filter {
private FilterConfig config;
public void destroy() {
}
public void doFilter(ServletRequest request, ServletResponse response,
FilterChain chain) throws IOException, ServletException {
/*
* 1. 得到application中的map
* 2. 从request中获取当前客户端的ip地址
* 3. 查看map中是否存在这个ip对应访问次数，如果存在，把次数+1再保存回去
* 4. 如果不存在这个ip，那么说明是第一次访问本站，设置访问次数为1
*/
/*
* 1. 得到appliction
*/
ServletContext app = config.getServletContext();
Map<String,Integer> map = (Map<String, Integer>) app.getAttribute("map");
/*
* 2. 获取客户端的ip地址
*/
String ip = request.getRemoteAddr();
/*
* 3. 进行判断
*/
if(map.containsKey(ip)) {//这个ip在map中存在，说明不是第一次访问
int cnt = map.get(ip);
map.put(ip, cnt+1);
} else {//这个ip在map中不存在，说明是第一次访问
map.put(ip, 1);
}
app.setAttribute("map", map);//把map再放回到app中
chain.doFilter(request, response);//肯定放行
}
/**
* 在服务器启动时就会执行本方法，而且本方法只执行一次！
*/
public void init(FilterConfig fConfig) throws ServletException {
this.config = fConfig;
}
}
web.xml
<?xml version="1.0" encoding="UTF-8"?> <web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" version="2.5"> <display-name></display-name> <welcome-file-list> <welcome-file>index.jsp</welcome-file> </welcome-file-list> <filter> <display-name>AFilter</display-name> <filter-name>AFilter</filter-name> <filter-class>cn.itcast.web.filter.AFilter</filter-class> </filter> <filter-mapping> <filter-name>AFilter</filter-name> <url-pattern>/*</url-pattern> </filter-mapping> <listener> <listener-class>cn.itcast.web.listener.AListener</listener-class> </listener> </web-app>
页面
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>My JSP 'show.jsp' starting page</title>
<meta http-equiv="pragma" content="no-cache">
<meta http-equiv="cache-control" content="no-cache">
<meta http-equiv="expires" content="0">
<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="This is my page">
<!--
<link rel="stylesheet" type="text/css" href="styles.css">
-->
</head>
<body>
<h1 align="center">显示结果</h1>
<table align="center" width="60%" border="1">
<tr>
<th>IP</th>
<th>次数</th>
</tr>
<c:forEach items="${applicationScope.map }" var="entry">
<tr>
<td>${entry.key }</td>
<td>${entry.value }</td>
</tr>
</c:forEach>
</table>
</body>
</html>
本文出自 “点滴积累” 博客，请务必保留此出处http://tianxingzhe.blog.51cto.com/3390077/1728685
