public class MD5ServletInputStream extends ServletInputStream {

    private final ServletInputStream input;
    private final MessageDigest md5;

    {
      try {
          md5 = MessageDigest.getInstance("MD5");
      } catch (NoSuchAlgorithmException e) {
          throw new ExceptionInInitializerError(e);
      }
    }

    public MD5ServletInputStream(ServletInputStream input) {
      this.input = input;
    }

    public byte[] getHash() {
      return md5.digest();
    }

    @Override
    public int read() throws IOException {
      int read = input.read();
      if (read != -1) {
          md5.update((byte) read);
      }
      return read;
    }

    public int read(byte b[]) throws IOException {
      int read = input.read(b, 0, b.length);
      if (read != -1) {
          md5.update(b);
      }
      return read;
    }

    public int read(byte b[], int off, int len) throws IOException {
      int read = input.read(b, off, len);
      if (read != -1) {
          md5.update(b);
      }
      return read;
    }
}

public class MD5ServletRequest extends HttpServletRequestWrapper {

    private final MD5ServletInputStream input;
    private byte[] bytes = null;
    
    public MD5ServletRequest(HttpServletRequest request) throws IOException {
      super(request);
      input = new MD5ServletInputStream(request.getInputStream());
    }

    public ServletInputStream getInputStream() throws IOException {
      return input;
    }

    public byte[] getHash() {
      return input.getHash();
    }

    public BufferedReader getReader() throws IOException {
      return new BufferedReader(new InputStreamReader(getInputStream()));
    }
    
    public String getMD5() {
      byte[] hash = getHash();
      StringBuilder hashAsHexString = new StringBuilder(
            hash.length * 2);
      for (byte b : hash) {
          hashAsHexString.append(String.format("%02x", b));
      }
      return hashAsHexString.toString();
    }
}

    public void doFilter(ServletRequest request, ServletResponse response,
          FilterChain chain) throws IOException, ServletException {
      
      HttpServletRequest httpRequest = (HttpServletRequest) request;
      MD5ServletRequest md5Request = new MD5ServletRequest(httpRequest);

      chain.doFilter(md5Request, response);

    }