java 全站压缩 过滤器

[java]代码库

package cn.itcast.filter;

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.util.zip.GZIPOutputStream;

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;
import javax.servlet.http.HttpServletResponseWrapper;

public class GZIPFilter implements Filter {

    public void destroy() {
    }
    public void doFilter(ServletRequest request, ServletResponse response,
            FilterChain chain) throws IOException, ServletException {
        //要想压缩页面 就是当用户访问页面时 在服务器把页面信息打给浏览器的时候进行压缩 所以这时候就是对response进行包装
        MyResponse myresponse = new MyResponse((HttpServletResponse) response);
        chain.doFilter(request, (ServletResponse) myresponse);
        //从包装的myresponse里获得写到容器流里的原始数据bs
        byte[] bs = myresponse.getOut();
        System.out.println("压缩前>>>"+bs.length);
        //用原始的response响应用户，此response需要转换为HttpServletResponse类型
        HttpServletResponse resp = (HttpServletResponse) response;
        //response解决中文乱码问题
        resp.setContentType("text/html;charset=utf-8");
        //开始压缩
        ByteArrayOutputStream out = new ByteArrayOutputStream();
        GZIPOutputStream zip = new GZIPOutputStream(out);
        zip.write(bs);
        zip.close();
        //获取压缩后的数据
        byte[] dest = out.toByteArray();
        System.out.println("压缩后>>>"+dest.length);
        //设置响应头
        resp.setDateHeader("content-length", dest.length);
        resp.setHeader("content-Encoding", "gzip");
        resp.getOutputStream().write(dest);
    }

    public void init(FilterConfig arg0) throws ServletException {
    }

}
class MyResponse extends HttpServletResponseWrapper{
    private ByteArrayOutputStream out = new ByteArrayOutputStream();//定义一个容器
    public MyResponse(HttpServletResponse response) {
        super(response);
    }
    //重写父类的getwriter方法
     PrintWriter writer;
    @Override
    public PrintWriter getWriter() throws IOException {
        //写到一个容器流里  ，
        writer = new PrintWriter(new OutputStreamWriter(out,"utf-8"), true);
        return writer;
    }
    //提供一个获得流里内容的方法    因为用字符流写到容器里的，有缓冲区,所以在取出流里的数据时判断字符流是否关闭
    public byte[] getOut(){
        if(writer!=null){
            writer.close();
        }
        return out.toByteArray();
    }   
}

<?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">
  <display-name></display-name> 
  <filter>
    <filter-name>GZIP</filter-name>
    <filter-class>cn.itcast.filter.GZIPFilter</filter-class>
  </filter>
  <filter-mapping>
    <filter-name>GZIP</filter-name>
    <url-pattern>*.jsp</url-pattern>
  </filter-mapping>
  <welcome-file-list>
    <welcome-file>index.jsp</welcome-file>
  </welcome-file-list>
</web-app>
//该片段来自于http://yuncode.net