java servlet 过滤器

来源：互联网发布：淘宝商品自检编辑：程序博客网时间：2024/05/16 12:48

功能：实现自增记录登录人数

源码：

1、结构

2、CountFilter

import java.io.IOException;import javax.servlet.*;import javax.servlet.http.HttpServletRequest;public class CountFilter implements Filter {private int count;@Overridepublic void destroy() {// TODO Auto-generated method stub}@Overridepublic void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)throws IOException, ServletException {// TODO Auto-generated method stubcount++;HttpServletRequest req=(HttpServletRequest) request;ServletContext context=req.getSession().getServletContext();context.setAttribute("count", count);chain.doFilter(request, response);}@Overridepublic void init(FilterConfig filterConfig) throws ServletException {// TODO Auto-generated method stubString param=filterConfig.getInitParameter("count");count=Integer.valueOf(param);}}

3、 index

<%@ page language="java" contentType="text/html; charset=GB18030"    pageEncoding="GB18030"%><!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"><html><head><meta http-equiv="Content-Type" content="text/html; charset=GB18030"><title>欢迎</title></head><body><h2>您好<%=application.getAttribute("count") %>位访客</h2></body>

4、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" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" id="WebApp_ID" version="3.0">  <display-name>JavaWeb9.3</display-name>  <welcome-file-list>    <welcome-file>index.html</welcome-file>    <welcome-file>index.htm</welcome-file>    <welcome-file>index.jsp</welcome-file>    <welcome-file>default.html</welcome-file>    <welcome-file>default.htm</welcome-file>    <welcome-file>default.jsp</welcome-file>  </welcome-file-list>  <filter>  <filter-name>CountFilter</filter-name>  <filter-class>CountFilter</filter-class>  <init-param>  <param-name>count</param-name>  <param-value>5000</param-value>  </init-param>  </filter>  <filter-mapping>  <filter-name>CountFilter</filter-name>  <url-pattern>/index.jsp</url-pattern>  </filter-mapping></web-app>

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