通过过滤器控制静态资源的缓存时间

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1。StaticResourcesNeedCacheFilter.java文件：

package com.itheima.example;import java.io.IOException;import javax.servlet.Filter;import javax.servlet.FilterChain;import javax.servlet.FilterConfig;import javax.servlet.ServletException;import javax.servlet.ServletRequest;import javax.servlet.ServletResponse;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;//控制静态资源的缓存时间public class StaticResourcesNeedCacheFilter implements Filter {    private FilterConfig filterConfig;    public void init(FilterConfig filterConfig) throws ServletException {        this.filterConfig = filterConfig;    }    public void doFilter(ServletRequest req, ServletResponse resp,            FilterChain chain) throws IOException, ServletException {        HttpServletRequest request = null;        HttpServletResponse response = null;        try{            request  = (HttpServletRequest)req;            response = (HttpServletResponse)resp;        }catch(Exception e){            throw new RuntimeException("not-http request or response");        }        long time = 0;//缓存的时间        //根据用户请求的uri地址的后缀：/day19_00_filter/1.html        String uri  = request.getRequestURI();        String exName = uri.substring(uri.lastIndexOf(".")+1);        if("html".equals(exName)){            String value = filterConfig.getInitParameter("html");//小时            time = Long.parseLong(value)*60*60*1000;        }        if("css".equals(exName)){            String value = filterConfig.getInitParameter("css");//小时            time = Long.parseLong(value)*60*60*1000;        }        if("js".equals(exName)){            String value = filterConfig.getInitParameter("js");//小时            time = Long.parseLong(value)*60*60*1000;        }        response.setDateHeader("Expires", System.currentTimeMillis()+time);        chain.doFilter(request, response);    }    public void destroy() {    }}

2。web.xml文件：

<?xml version="1.0" encoding="UTF-8"?><web-app version="3.0"    xmlns="http://java.sun.com/xml/ns/javaee"    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"    xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"><welcome-file-list>    <welcome-file>index.jsp</welcome-file></welcome-file-list><filter>    <filter-name>SetCharacterEncodingFilter</filter-name>    <filter-class>com.itheima.encoding.SetCharacterEncodingFilter</filter-class>    <init-param>        <param-name>encoding</param-name>        <param-value>UTF-8</param-value>    </init-param> </filter>   <filter-mapping><!-- 按照此标签的出现顺序 -->    <filter-name>SetCharacterEncodingFilter</filter-name>    <url-pattern>/*</url-pattern> </filter-mapping><filter>    <filter-name>StaticResourcesNeedCacheFilter</filter-name>    <filter-class>com.itheima.example.StaticResourcesNeedCacheFilter</filter-class>    <init-param>        <param-name>html</param-name>        <param-value>1</param-value>    </init-param>    <init-param>        <param-name>css</param-name>        <param-value>2</param-value>    </init-param>    <init-param>        <param-name>js</param-name>        <param-value>3</param-value>    </init-param></filter>    <filter-mapping><!-- 按照此标签的出现顺序 -->    <filter-name>StaticResourcesNeedCacheFilter</filter-name>    <url-pattern>*.html</url-pattern></filter-mapping><filter-mapping><!-- 按照此标签的出现顺序 -->    <filter-name>StaticResourcesNeedCacheFilter</filter-name>    <url-pattern>*.css</url-pattern></filter-mapping><filter-mapping><!-- 按照此标签的出现顺序 -->    <filter-name>StaticResourcesNeedCacheFilter</filter-name>    <url-pattern>*.js</url-pattern></filter-mapping></web-app>

3。1.html文件：

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html>  <head>    <title>1.html</title>    <meta http-equiv="keywords" content="keyword1,keyword2,keyword3">    <meta http-equiv="description" content="this is my page">    <meta http-equiv="content-type" content="text/html; charset=UTF-8">    <link rel="stylesheet" type="text/css" href="main.css">    <script type="text/javascript" src="1.js"></script>  </head>  <body>    希希哥遇到了茜茜姐  </body></html>

4。1.jsp文件：

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html>  <head>    <title>title</title>    <meta http-equiv="pragma" content="no-cache">    <meta http-equiv="cache-control" content="no-cache">    <meta http-equiv="expires" content="0">    <!--    <link rel="stylesheet" type="text/css" href="styles.css">    -->  </head>  <body>    <form action="${pageContext.request.contextPath}/servlet/ServletDemo2" method="post">        <input type="text" name="name"/><input type="submit" value="保存"/>    </form>  </body></html>

5。1.js文件：

alert("啊哈哈哈");

6。main.css文件：

body{    color: blue;

7。运行：http://localhost:8080/Filter_project/1.html
8.结果：
弹出了“啊哈哈哈”的对话框，
输出了：希希哥遇到了茜茜姐

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