网站图片(gif,jpg等),css,js等不常改变的,可以考虑使用过滤器技术进行缓存
/*--------------------------XML---------------------*/
<filter>
<filter-name>CacheFilter</filter-name>
<filter-class>cn.itcast.filter.CacheFilter</filter-class>
<init-param>
<param-name>jpg</param-name>
<param-value>5</param-value>
</init-param>
<init-param>
<param-name>gif</param-name>
<param-value>5</param-value>
</init-param>
<init-param>
<param-name>js</param-name>
<param-value>5</param-value>
</init-param>
<init-param>
<param-name>css</param-name>
<param-value>5</param-value>
</init-param>
</filter>
<filter-mapping>
<filter-name>CacheFilter</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>
/*--------------------------过滤器---------------------*/import java.io.IOException;
import java.util.Date;
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 CacheFilter implements Filter {
private FilterConfig filterconfig;
public void destroy() {
}
public void doFilter(ServletRequest request, ServletResponse response,
FilterChain chain) throws IOException, ServletException {
//1.强转httpservlet,方便调用方法
HttpServletRequest req = (HttpServletRequest) request;
HttpServletResponse res = (HttpServletResponse) response;
//2.获取资源文件名的URI
String uri = req.getRequestURI();
//3.获得文件扩展名,lastIndexOf(".")+1 获得.最后一次出现的索引的后一位:jpg
uri = uri.substring(uri.lastIndexOf(".")+1);
System.out.println( uri );//测试获取后缀是否正确
//4断相应后缀文件,设定缓存时间
long date = 0;
//System.out.println( new Date().getTime());//测试当前时间用
//判断URI获取的后缀名是否与JPG相等,不考虑大小写
if(uri.equalsIgnoreCase("jpg")){
//读取XML里的JPG配置的参数,这里设定了时间
String value = filterconfig.getInitParameter("jpg");
//获取当前系统时间 + 需要缓存的时间(小时),Long 防止溢出,因为单位是毫秒
date = System.currentTimeMillis()+Long.parseLong(value)*60*60*1000;
}
if(uri.equalsIgnoreCase("gif")){
//读取XML里的JPG配置的参数,这里设定了时间
String value = filterconfig.getInitParameter("gif");
//获取当前系统时间 + 需要缓存的时间(小时),Long 防止溢出,因为单位是毫秒
date = System.currentTimeMillis()+Long.parseLong(value)*60*60*1000;
}
if(uri.equalsIgnoreCase("css")){
//读取XML里的JPG配置的参数,这里设定了时间
String value = filterconfig.getInitParameter("css");
//获取当前系统时间 + 需要缓存的时间(小时),Long 防止溢出,因为单位是毫秒
date = System.currentTimeMillis()+Long.parseLong(value)*60*60*1000;
}
if(uri.equalsIgnoreCase("js")){
//读取XML里的JPG配置的参数,这里设定了时间
String value = filterconfig.getInitParameter("js");
//获取当前系统时间 + 需要缓存的时间(小时),Long 防止溢出,因为单位是毫秒
date = System.currentTimeMillis()+Long.parseLong(value)*60*60*1000;
}
//设置缓存时间
res.setDateHeader("Expires", date);
chain.doFilter(req, res);
}
public void init(FilterConfig filterConfig) throws ServletException {
this.filterconfig = filterConfig;
}
}
/*---------------测试页面-----------------*/
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<html>
<head>
<title>Insert title here</title>
</head>
<body>
<img alt="" src="123.gif">
</body></html>