具体的Filter实现

public class GzipFilter implements Filter {    public void doFilter(ServletRequest req, ServletResponse resp,            FilterChain chain) throws IOException, ServletException {                HttpServletRequest request = (HttpServletRequest) req;        HttpServletResponse response = (HttpServletResponse) resp;        MyResponse myresponse = new MyResponse(response);                        chain.doFilter(request, myresponse);  //response.getwriter  response.getOutputStream                  //取出缓冲的数据压缩后输出        byte out[] = myresponse.getBuffer();  //得到目标资源的输出        System.out.println("压之前：" + out.length);                        byte gzipout[] = gzip(out);        System.out.println("压之后：" + gzipout.length);                response.setHeader("content-encoding", "gzip");        response.setHeader("content-length", gzipout.length + "");        response.getOutputStream().write(gzipout);    }        public byte[] gzip(byte b[]) throws IOException{                ByteArrayOutputStream bout = new ByteArrayOutputStream();        GZIPOutputStream gout = new GZIPOutputStream(bout);        gout.write(b);        gout.close();        return bout.toByteArray();    }        class MyResponse extends HttpServletResponseWrapper{        private ByteArrayOutputStream bout = new ByteArrayOutputStream();        private PrintWriter pw;                private HttpServletResponse response;        public MyResponse(HttpServletResponse response) {            super(response);            this.response = response;        }        @Override        public ServletOutputStream getOutputStream() throws IOException {            return new MyServletOutputStream(bout);    //myresponse.getOutputStream().write("hahah");        }                @Override        public PrintWriter getWriter() throws IOException {            pw = new PrintWriter(new OutputStreamWriter(bout,response.getCharacterEncoding()));            return pw;  //MyResponse.getWriter().write("中国");        }        public byte[] getBuffer(){            if(pw!=null){                pw.close();            }            return bout.toByteArray();        }    }        class MyServletOutputStream extends ServletOutputStream{        private ByteArrayOutputStream bout;        public MyServletOutputStream(ByteArrayOutputStream bout){            this.bout = bout;        }        @Override        public void write(int b) throws IOException {            bout.write(b);        }            }    public void destroy() {        // TODO Auto-generated method stub    }        public void init(FilterConfig filterConfig) throws ServletException {        // TODO Auto-generated method stub    }}