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;        //聲明包裝類對象        MyResponse2 myresp = new MyResponse2(resp);        //放行,調用oneServlet.doGet        chain.doFilter(request, myresp);                 //第二步：從myresp2中讀取原生的數據        byte[] src = myresp.getSrc();                 //第三步：開始壓縮        ByteArrayOutputStream destBytes = new ByteArrayOutputStream();        GZIPOutputStream zip = new GZIPOutputStream(destBytes);        zip.write(src);        zip.close();                //第三步：輸出-使用原生的response        resp.setContentType("text/html;charset=UTF-8");        //獲壓縮以后數據        byte[] dest = destBytes.toByteArray();        System.err.
//第一步：聲明response的包裝類class MyResponse2 extends HttpServletResponseWrapper{    //將這個容器/a.txt,聲明成員變量    private ByteArrayOutputStream srcByte;    public MyResponse2(HttpServletResponse response) {        super(response);    }    //修改增強getWtier方法    @Override    public PrintWriter getWriter() throws IOException {        srcByte = new ByteArrayOutputStream();        PrintWriter out =                 new PrintWriter(                        new OutputStreamWriter(srcByte, "UTF-8"));        return out;    }    //提供一個方法獲取原生 的數據    public byte[] getSrc(){        return srcByte.toByteArray();    }}
第五步：全部的jsp都要經過壓縮
只要是通過包裝rersponse，且修改了getWriter方法，返回一個自己的printwiter對象。聲明一個放原數據的容器對象。就可以實現數據壓縮。
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;        //聲明包裝類對象        MyResponse2 myresp = new MyResponse2(resp);        //放行,調用oneServlet.doGet        chain.doFilter(request, myresp);                //第二步：從myresp2中讀取原生的數據        byte[] src = myresp.getSrc();                //第三步：開始壓縮        ByteArrayOutputStream destBytes = new ByteArrayOutputStream();        GZIPOutputStream zip = new GZIPOutputStream(destBytes);        zip.write(src);        zip.close();                //第三步：輸出-使用原生的response        resp.setContentType("text/html;charset=UTF-8");        //獲壓縮以后數據        byte[] dest = destBytes.toByteArray();        System.err.println("壓縮之前："+src.length);        System.err.println("壓縮以后："+dest.length);        //設置頭        resp.setContentLength(dest.length);        resp.setHeader("Content-Encoding","gzip");        //輸出        OutputStream out = resp.getOutputStream();        out.write(dest);                }    public void destroy() {    }}
//第一步：聲明response的包裝類class MyResponse2 extends HttpServletResponseWrapper{    //將這個容器/a.txt,聲明成員變量    private ByteArrayOutputStream srcByte;    private PrintWriter out;     public MyResponse2(HttpServletResponse response) {        super(response);    }    //修改增強getWtier方法    @Override    public PrintWriter getWriter() throws IOException {        srcByte = new ByteArrayOutputStream();        out =                 new PrintWriter(                        new OutputStreamWriter(srcByte, "UTF-8"));        return out;    }    //提供一個方法獲取原生 的數據    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>
同時實現對getoutputstream和getWtier壓縮
在myrespons2這個類中，對getoutputstream也要覆蓋。
 返回一個ServletOutputSteam的匿名對象。
 實現witer(int b)方法，將數據寫到bytearrayoyutpoutstream.
 public ServletOutputStream getOutputStream() throws IOException {
 srcByte = new ByteArrayOutputStream();
 ServletOutputStream out = new ServletOutputStream() {
 //所有IO最終都是一個個字節寫出信息
 @Override
 public void write(int b) throws IOException {
 System.err.println(">>>:"+b);
 srcByte.write(b);//寫到自己的緩存中去-相當于StringBuffer.append(""+b);
 }
 };
 return out;
 }