code: public static String getPostData(HttpServletRequest request) throws IOException {
          BufferedReader br = new BufferedReader(new InputStreamReader(request.getInputStream()));
          String line;
          StringBuilder sb = new StringBuilder();
          while ((line = br.readLine()) != null) {
              sb.append(line);
          }
          //return URLDecoder.decode(sb.toString(), Constant.DEFAULT_CHATSET);
          return sb.toString();
      }
docs: 如果客户端通过 request 传递数据，那么就可以使用该方法获取数据
  这种通常是通过 Post方式
  @param request HttpServletRequest
  @return 客户端上传的数据
  @throws IOException 因为是通过IO流读取数据，
  因此很可能读取失败，或者NULL，导致抛出IO异常，