java—数据的压缩2 （52）

第四步：修改包装类Myresponse2，让输出数据放到一个内存缓存区中

package cn.hongxin.filter;



public class GzipFilter2 implements Filter {

    public void init(FilterConfig filterConfig) throws ServletException {

    }



    public void doFilter(ServletRequest request, ServletResponse response,

            FilterChain chain) throws IOException, ServletException {

        HttpServletResponse resp= (HttpServletResponse) response;

        //声明包装类对象

        MyResponse2 myresp = new MyResponse2(resp);

        //放行,调用oneServlet.doGet

        chain.doFilter(request, myresp);

         

        //第二步：从myresp2中读取原生的数据

        byte[] src = myresp.getSrc(); 

        

        //第三步：开始压缩

        ByteArrayOutputStream destBytes = new ByteArrayOutputStream();

        GZIPOutputStream zip = new GZIPOutputStream(destBytes);

        zip.write(src);

        zip.close();

        

        //第三步：输出-使用原生的response

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

        //获压缩以后数据

        byte[] dest = destBytes.toByteArray();

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

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

        //设置头

        resp.setContentLength(dest.length);

        resp.setHeader("Content-Encoding","gzip");

        //输出

        OutputStream out = resp.getOutputStream();

        out.write(dest);

    }

    public void destroy() {

    }

}

//第一步：声明response的包装类

class MyResponse2 extends HttpServletResponseWrapper{

    //将这个容器/a.txt,声明成员变量

    private ByteArrayOutputStream srcByte;

    public MyResponse2(HttpServletResponse response) {

        super(response);

    }

    //修改增强getWtier方法

    @Override

    public PrintWriter getWriter() throws IOException {

        srcByte = new ByteArrayOutputStream();

        PrintWriter out = 

                new PrintWriter(

                        new OutputStreamWriter(srcByte, "UTF-8"));

        return out;

    }

    //提供一个方法获取原生 的数据

    public byte[] getSrc(){

        return srcByte.toByteArray();

    }

}

第五步：全部的jsp都要经过压缩

只要是通过包装rersponse，且修改了getWriter方法，返回一个自己的printwiter对象。声明一个放原数据的容器对象。就可以实现数据压缩。

public class GzipFilter2 implements Filter {

    public void init(FilterConfig filterConfig) throws ServletException {

    }



    public void doFilter(ServletRequest request, ServletResponse response,

            FilterChain chain) throws IOException, ServletException {

        HttpServletResponse resp= (HttpServletResponse) response;

        //声明包装类对象

        MyResponse2 myresp = new MyResponse2(resp);

        //放行,调用oneServlet.doGet

        chain.doFilter(request, myresp);

        

        //第二步：从myresp2中读取原生的数据

        byte[] src = myresp.getSrc();

        

        //第三步：开始压缩

        ByteArrayOutputStream destBytes = new ByteArrayOutputStream();

        GZIPOutputStream zip = new GZIPOutputStream(destBytes);

        zip.write(src);

        zip.close();

        

        //第三步：输出-使用原生的response

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

        //获压缩以后数据

        byte[] dest = destBytes.toByteArray();

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

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

        //设置头

        resp.setContentLength(dest.length);

        resp.setHeader("Content-Encoding","gzip");

        //输出

        OutputStream out = resp.getOutputStream();

        out.write(dest);

        

    

    }

    public void destroy() {

    }



}

//第一步：声明response的包装类

class MyResponse2 extends HttpServletResponseWrapper{

    //将这个容器/a.txt,声明成员变量

    private ByteArrayOutputStream srcByte;

    private PrintWriter out; 

    public MyResponse2(HttpServletResponse response) {

        super(response);

    }

    //修改增强getWtier方法

    @Override

    public PrintWriter getWriter() throws IOException {

        srcByte = new ByteArrayOutputStream();

        out = 

                new PrintWriter(

                        new OutputStreamWriter(srcByte, "UTF-8"));

        return out;

    }

    //提供一个方法获取原生 的数据

    public byte[] getSrc(){

        if(out!=null){

            out.close();

        }

         return srcByte.toByteArray();

    }

}

且它的配置如下：

<filter>

    <filter-name>zip2</filter-name>

    <filter-class>cn.itcast.filter.GzipFilter2</filter-class>

  </filter>

  <filter-mapping>

    <filter-name>zip2</filter-name>

    <url-pattern>*.jsp</url-pattern>

  </filter-mapping>

同时实现对getoutputstream和getWtier压缩

在myrespons2这个类中，对getoutputstream也要覆盖。

       返回一个ServletOutputSteam的匿名对象。

       实现witer(int b)方法，将数据写到bytearrayoyutpoutstream.

    public ServletOutputStream getOutputStream() throws IOException {

       srcByte = new ByteArrayOutputStream();

       ServletOutputStream out = new ServletOutputStream() {

           //所有IO最终都是一个个字节写出信息

           @Override

           public void write(int b) throws IOException {

              System.err.println(">>>:"+b);

              srcByte.write(b);//写到自己的缓存中去-相当于StringBuffer.append(""+b);

           }

       };

       return out;

    }