web中gzip,deflate的压缩与解压

一，对发送请求进行gzip,deflate压缩

1:gzip的情况

 Sring url = "http://localhost/save";
 PostMethod post = new PostMethod(url);
 //请求体内容
 String body = "sample";
 //用gzip方式压缩请求体并赋给request
 ByteArrayInputStream bis = new ByteArrayInputStream(body.getBytes());
 ByteArrayOutputStream bos = new ByteArrayOutputStream();
 GZIPOutputStream gos = new GZIPOutputStream(bos);
 for (int c = bis.read(); c != -1; c = bis.read()) {
     gos.write(c);
 }
 gos.close();
 InputStreamRequestEntity entity = new InputStreamRequestEntity(new ByteArrayInputStream(bos.toByteArray()), "text/html");
 post.setRequestEntity(entity);
 post.addRequestHeader("Content-Encoding", "gzip");

 

2:deflate的情况

 Sring url = "http://localhost/save";
 PostMethod post = new PostMethod(url);
 //请求体内容
 String body = "sample";
 //用deflate方式压缩请求体并赋给request
 ByteArrayInputStream bis = new ByteArrayInputStream(body.getBytes());
 ByteArrayOutputStream bos = new ByteArrayOutputStream();
 DeflaterOutputStream dos = new DeflaterOutputStream(bos);
 for (int c = bis.read(); c != -1; c = bis.read()) {
     dos.write(c);
 }
 dos.close();
 InputStreamRequestEntity entity = new InputStreamRequestEntity(new ByteArrayInputStream(bos.toByteArray()), "text/html");
 post.setRequestEntity(entity);
 post.addRequestHeader("Content-Encoding", "deflate");

 

二，在服务器端使用过滤器对压缩过的请求进行解压

新建一个filter继承UserAgentFilter.java,截取req,进行包装，接着继续执行别的filters

 @Override
 public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain) throws IOException,
     ServletException {
     HttpServletRequest request = (HttpServletRequest) req;
     String ce = request.getHeader("Content-Encoding"); // gzip|deflate|inflate
     if (ce != null) {
         if (ce.indexOf("deflate") >= 0 || ce.indexOf("inflate") >= 0) {
         // uncompress using inflate
         request = new InflateRequestWrapper(request);
         } else if (ce.indexOf("gzip") >= 0) {
         // uncompress using gzip
         request = new GZipRequestWrapper(request);
         }
     }
     ......
     super.doFilter(request, res, chain);
     ......
 }

 

下面是InflateRequestWrapper的内容，GZipRequestWrapper与之类似

 public class InflateRequestWrapper extends HttpServletRequestWrapper {
     private BufferedServletInputStreamWrapper _stream;

     public InflateRequestWrapper(HttpServletRequest request) throws IOException {
         super(request);
         _stream = new BufferedServletInputStreamWrapper(new InflaterInputStream(request.getInputStream()), request.getContentLength());
     }

     @Override
     public BufferedServletInputStreamWrapper getInputStream() {
         return _stream;
     }

     @Override
     public int getContentLength() {
         return _stream.getBytes().length;
     }
 }

 

下面是BufferedServletInputStreamWrapper的内容

 public class BufferedServletInputStreamWrapper extends ServletInputStream {

     private static final int DEFAULT_READ_BUFFER_SIZE = 1024;
     private final byte[] EMPTY_ARRAY = new byte[0];
     private ByteArrayInputStream _is;
     private byte[] _bytes;

     /**
      * takes in the actual input stream that we should be buffering
      */
     public BufferedServletInputStreamWrapper(InflaterInputStream stream, int length) throws IOException {
         _bytes = (length == 0) ? EMPTY_ARRAY : toBytes(stream, length);
         _is = new ByteArrayInputStream(_bytes);
     }

     @Override
     public int read() throws IOException {
         return _is.read();
     }

     @Override
     public int read(byte[] buf,
                     int off,
                     int len) {
         return _is.read(buf, off, len);
     }

     @Override
     public int read(byte[] buf) throws IOException {
         return _is.read(buf);
     }

     @Override
     public int available() {
         return _is.available();
     }

     /**
      * resets the wrapper's stream so that it can be re-read from the stream. if we're
      * using this somewhere were we expect it to be done again in the chain this should
      * be called after we're through so we can reset the data.
      */

     public void resetWrapper() {
         _is = new ByteArrayInputStream(_bytes);
     }

     public byte[] getBytes() {
         return _bytes;
     }

     private byte[] toBytes(InputStream is, int bufferSize) throws IOException {
         bufferSize = (bufferSize <= 0) ? DEFAULT_READ_BUFFER_SIZE : bufferSize;
         ByteArrayOutputStream bos = new ByteArrayOutputStream();
         byte[] buffer = new byte[bufferSize];
         int read = is.read(buffer);

         while (-1 != read) {
             bos.write(buffer, 0, read);
             read = is.read(buffer);
         }

         return bos.toByteArray();
     }
 }

 

三，服务器对response进行压缩可参考jetty相关源码

 

四，java客户端对压缩过的返回值进行解压

1,gzip的情况

 GZIPInputStream gzip = new GZIPInputStream(post.getResponseBodyAsStream());
 StringBuffer out = new StringBuffer();
 byte[] b = new byte[4096];
 for (int n; (n = gzip.read(b)) != -1;) {
     out.append(new String(b, 0, n));
 }
 return out.toString();

 

2，deflate的情况

 InflaterInputStream iis = new InflaterInputStream(post.getResponseBodyAsStream());
 contentLength = (contentLength <= 0) ? 1024 : contentLength;
 ByteArrayOutputStream bos = new ByteArrayOutputStream();
 byte[] buffer = new byte[contentLength];
 int read = iis.read(buffer);

 while (-1 != read) {
     bos.write(buffer, 0, read);
     read = iis.read(buffer);
 }

 byte[] _bytes = (contentLength == 0) ? EMPTY_ARRAY : bos.toByteArray();
 ByteArrayInputStream _is = new ByteArrayInputStream(_bytes);

 StringBuffer out = new StringBuffer();
 byte[] b = new byte[4096];
 for (int n; (n = _is.read(b)) != -1;) {
     out.append(new String(b, 0, n));
 }
 return out.toString();

 原地址：http://crazysky.iteye.com/blog/775333