过滤器压缩全站jsp

过滤器：

 1 public class Gzip implements Filter {
 2 
 3     public void destroy() {}
 4 
 5     public void doFilter(ServletRequest request, ServletResponse response,
 6             FilterChain chain) throws IOException, ServletException {
 7         HttpServletResponse resp=(HttpServletResponse) response;
 8         MyResp myResp=new MyResp(resp);//包装过的response
 9         chain.doFilter(request, myResp);//放行
10         
11         byte[] srcBytes= myResp.getSrcByte();//获取源数据
12         ByteArrayOutputStream bOutStream=new ByteArrayOutputStream();//目标容器
13         GZIPOutputStream zipOutStream=new GZIPOutputStream(bOutStream);//压缩工具
14         zipOutStream.write(srcBytes);//写到容器中
15         zipOutStream.close();//如果不关闭，会在缓存中，不写出
16         
17         byte[] descByte=bOutStream.toByteArray();
18         
19         System.out.println("-------------------");
20         System.out.println("压缩前："+srcBytes.length);
21         System.out.println("压缩后："+ descByte.length);
22         System.out.println("-------------------");
23         
24         //使用原生response输出
25         resp.setContentType("text/html;charset=utf-8");
26         resp.setHeader("Content-Encoding", "Gzip");
27         resp.setContentLength(srcBytes.length);
28         
29         //输出
30         OutputStream out=resp.getOutputStream();
31         out.write(descByte);//关闭
32         
33         
34     }
35     public void init(FilterConfig filterConfig) throws ServletException {}
36 
37 }
38 
39 class MyResp extends HttpServletResponseWrapper
40 {
41     private  PrintWriter outWrite;
42     private ByteArrayOutputStream srcByte;
43     //获取原生数据
44     public byte[] getSrcByte() {
45         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
46         {
47             outWrite.close();
48         }
49         return srcByte.toByteArray();
50     }
51 
52     public MyResp(HttpServletResponse response) {
53         super(response);
54 
55     }
56 
57     //包装getWrite()方法，jsp页面输出内容使用的是response.getWriter().write（""）
58     //所以要包装
59     @Override
60     public PrintWriter getWriter() throws IOException {
61         srcByte=new ByteArrayOutputStream();//输出的源数据
62         outWrite=new PrintWriter(new OutputStreamWriter(srcByte,"utf-8"));        
63         return outWrite;
64     }
65     
66 }

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

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

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

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

包装getOutputStream()方法

 1     @Override
 2     public ServletOutputStream getOutputStream() throws IOException {
 3         srcByte =new ByteArrayOutputStream();//输出的源数据
 4         ServletOutputStream out=new ServletOutputStream() {            
 5             @Override
 6             public void write(int b) throws IOException {
 7                 srcByte.write(b);                
 8             }
 9         };
10         return out;
11     }