过滤器压缩全站jsp

过滤器：

 public class Gzip implements Filter {

     public void destroy() {}

     public void doFilter(ServletRequest request, ServletResponse response,
             FilterChain chain) throws IOException, ServletException {
         HttpServletResponse resp=(HttpServletResponse) response;
         MyResp myResp=new MyResp(resp);//包装过的response
         chain.doFilter(request, myResp);//放行

         byte[] srcBytes= myResp.getSrcByte();//获取源数据
         ByteArrayOutputStream bOutStream=new ByteArrayOutputStream();//目标容器
         GZIPOutputStream zipOutStream=new GZIPOutputStream(bOutStream);//压缩工具
         zipOutStream.write(srcBytes);//写到容器中
         zipOutStream.close();//如果不关闭，会在缓存中，不写出

         byte[] descByte=bOutStream.toByteArray();

         System.out.println("-------------------");
         System.out.println("压缩前："+srcBytes.length);
         System.out.println("压缩后："+ descByte.length);
         System.out.println("-------------------");

         //使用原生response输出
         resp.setContentType("text/html;charset=utf-8");
         resp.setHeader("Content-Encoding", "Gzip");
         resp.setContentLength(srcBytes.length);

         //输出
         OutputStream out=resp.getOutputStream();
         out.write(descByte);//关闭

     }
     public void init(FilterConfig filterConfig) throws ServletException {}

 }

 class MyResp extends HttpServletResponseWrapper
 {
     private  PrintWriter outWrite;
     private ByteArrayOutputStream srcByte;
     //获取原生数据
     public byte[] getSrcByte() {
         if(outWrite!=null)//如果不关闭流，不会显示，因为数据在缓存中，没有写出
         {
             outWrite.close();
         }
         return srcByte.toByteArray();
     }

     public MyResp(HttpServletResponse response) {
         super(response);

     }

     //包装getWrite()方法，jsp页面输出内容使用的是response.getWriter().write（""）
     //所以要包装
     @Override
     public PrintWriter getWriter() throws IOException {
         srcByte=new ByteArrayOutputStream();//输出的源数据
         outWrite=new PrintWriter(new OutputStreamWriter(srcByte,"utf-8"));
         return outWrite;
     }

 }

如果过滤器需要过滤Servlet，则需要用response.getWriter().write（""）输出，否则不会被过滤

 response.setContentType("text/html;charset=utf-8");
         String str="你好，同学；Hello World";
         PrintWriter writer=response.getWriter();
         writer.write(str);
         writer.close();

如果Servlet中使用response.getOutputStream().write("")输出，则需要包装getOutputStream()方法

 response.setContentType("text/html;charset=utf-8");
         String str="你好，同学；Hello World";
         String times=request.getParameter("times");
         int n=Integer.valueOf(times);
         OutputStream out=response.getOutputStream();
         for (int i = 0; i < n; i++) {
             out.write(str.getBytes("utf-8"));
         }
         out.close();

包装getOutputStream()方法

     @Override
     public ServletOutputStream getOutputStream() throws IOException {
         srcByte =new ByteArrayOutputStream();//输出的源数据
         ServletOutputStream out=new ServletOutputStream() {
             @Override
             public void write(int b) throws IOException {
                 srcByte.write(b);
             }
         };
         return out;
     }