code: private byte[] copyBytesFromRequest(HttpServletRequest httpServletRequest) throws IOException {
          InputStream inputStream = httpServletRequest.getInputStream();
          ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();
          byte[] buffer = new byte[1024];
          int offset=-1;
          while((offset=inputStream.read(buffer,0,1024))>0){
              byteArrayOutputStream.write(buffer,0,offset);
          }
          return byteArrayOutputStream.toByteArray();
      }
docs: 将request body的byte字节数组复制到内存中
  @param httpServletRequest
  @return
  @throws IOException