数据的压缩1 （51）

 : resp.,getWriter().print(…..);

public class OneServlet extends HttpServlet {

    public void doGet(HttpServletRequest request, HttpServletResponse response)

           throws ServletException, IOException {

       response.setContentType("text/html;charset=UTF-8");

       PrintWriter out = response.getWriter();

       out.println("Hello你好大家同学");

    }

}

第二步：对这上面的这个类进行拦截-Filter,在拦截过程中包装response

    实现抽像类：HttpServletResponseWrapper －
package cn.hongxin.filter;

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.HttpServletResponse;

import javax.servlet.http.HttpServletResponseWrapper;

public class GzipFilter implements Filter {

    public void init(FilterConfig filterConfig) throws ServletException {

    }

    public void doFilter(ServletRequest request, ServletResponse response,

           FilterChain chain) throws IOException, ServletException {

       //声明MyResponse包装类

       MyResponse resp = new MyResponse((HttpServletResponse) response);

       //放行时，必须要传递自己包装过的类

       chain.doFilter(request, resp);

    }

    public void destroy() {

    }

}

//实现对HttpSerlvetResponse的包装

class MyResponse extends HttpServletResponseWrapper{

    public MyResponse(HttpServletResponse response) {

       super(response);

    }

}

第三步：为了可以压缩数据，我们必须要拦截getwriter方法

       返回的不是apache的Wrtiter对象。

以下是完整的代码：

package cn.hongxing.filter;

public class GzipFilter implements Filter {

    public void init(FilterConfig filterConfig) throws ServletException {

    }

    public void doFilter(ServletRequest request, ServletResponse response,

           FilterChain chain) throws IOException, ServletException {

       //声明MyResponse包装类

       MyResponse resp = new MyResponse((HttpServletResponse) response);

       //放行时，必须要传递自己包装过的类

       chain.doFilter(request, resp);     

       //目标类调用完成了,返回 以后读取a.txt

       File file = new File("d:/a/a.txt");

       //声明一个缓存的字符串对象

       StringBuilder sb = new StringBuilder();

       //读取文件

       InputStream in = new FileInputStream(file);

       byte[] b = new byte[1024];

       int len = 0;

       while((len=in.read(b))!=-1){

           sb.append(new String(b,0,len,"UTF-8"));

       }

       in.close();

    //转成字节开始压缩

       byte[] src = sb.toString().getBytes("UTF-8");

       //声明缓存容器

       ByteArrayOutputStream destBytes = new ByteArrayOutputStream();

       //声明压缩流

       GZIPOutputStream gzip = new GZIPOutputStream(destBytes);

       //压缩数据

       gzip.write(src);

       gzip.close();

       //获取压缩以后数据

       byte[] dest = destBytes.toByteArray();

       System.err.println("压缩之前："+src.length);

       System.err.println("压缩以后："+dest.length);

      //输出

       //必须要使用原生 的response

       HttpServletResponse res = (HttpServletResponse) response;

       res.setContentType("text/html;charset=UTf-8");

       OutputStream out = res.getOutputStream();

       res.setHeader("Content-encoding", "gzip");//必须

       res.setContentLength(dest.length);

       out.write(dest);

    }

    public void destroy() {

    }

}

//实现对HttpSerlvetResponse的包装

class MyResponse extends HttpServletResponseWrapper{[W8] 

    public MyResponse(HttpServletResponse response) {

       super(response);

    }

    @Override

    public PrintWriter getWriter([W9] ) throws IOException {

       System.err.println("有人想获取输出流");

       PrintWriter out = new PrintWriter[W10] (

              new OutputStreamWriter(

                     new FileOutputStream("d:/a/a.txt"),"UTF-8"));

       return out;

    }

}