code: private void dumpInputStream(){
          //dump request body
          exchange.startBlocking();
          InputStream inputStream = exchange.getInputStream();
          try {
              if(config.isMaskEnabled() && inputStream.available() != -1) {
                  this.bodyContent = Mask.maskJson(inputStream, "requestBody");
              } else {
                  try {
                      this.bodyContent = StringUtils.inputStreamToString(inputStream, UTF_8);
                  } catch (IOException e) {
                      logger.error(e.toString());
                  }
              }
          } catch (IOException e) {
              logger.error("undertow inputstream error:" + e.getMessage());
          }
      }
docs: read from input stream, convert it to string, put into this.bodyContent