首先创建一个web project的项目,项目结构如下.
在WEB-INF里面添加一张rain.jpg的图片.
并且在WEB-INF里面新建一个demo1的文件夹,添加一个index.jsp的页面.
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>My JSP 'index.jsp' starting page</title>
</head>
<body>
<img src="/PictureCache/rain.jpg">
</body>
</html>
然后再新建一个包新建一个ImageCacheFilter(过滤器)的类.
package cn.itcast.filter.demo3;
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;
public class ImageCacheFilter implements Filter {
public void destroy() {
}
public void doFilter(ServletRequest req, ServletResponse resp,
FilterChain chain) throws IOException, ServletException {
// 1.强制转换
HttpServletRequest request = (HttpServletRequest) req;
HttpServletResponse response = (HttpServletResponse) resp;
// 2.操作
response.setDateHeader("expires", System.currentTimeMillis()+60*60*24*10*1000);//缓存10天
// 3.放行
chain.doFilter(request, response);
}
public void init(FilterConfig filterConfig) throws ServletException {
}
}
web.xml的文件配置.
<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.5"
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_2_5.xsd">
<filter>
<filter-name>imageFilter</filter-name>
<filter-class>cn.itcast.filter.demo3.ImageCacheFilter</filter-class>
</filter>
<filter-mapping>
<filter-name>imageFilter</filter-name>
<url-pattern>*.jpg</url-pattern>
</filter-mapping>
<welcome-file-list>
<welcome-file>index.jsp</welcome-file>
</welcome-file-list>
</web-app>