code: private static void check(Set<ConstraintViolation<Object>> constraintViolations) {
          Iterator<ConstraintViolation<Object>> iterator = constraintViolations.iterator();
          if (iterator.hasNext()) {
              throw new ValidationException(iterator.next().getMessage());
          }
      }
docs: 检查是否有校验错误
  
  @param constraintViolations 校验结果