code: public void validateOpts(Object instance) {
          final Set<ConstraintViolation<Object>> set = validator.validate(instance);
          final StringBuilder sb = new StringBuilder();
          for (ConstraintViolation<Object> violation : set) {
              final Path path = violation.getPropertyPath();
              final String msg = violation.getMessage();
              sb.append(path.toString()).append(" ").append(msg).append(". ");
          }
          if (sb.length() > 0) {
              // is ConstraintViolationException more appropriate,
              // letting user choose their error message?
              throw new ValidationException(OPT_VIOLATION_MSG + ": " + sb.toString());
          }
      }
docs: This method will only be called if we know that JSR 303 1.0 Bean Validation API
  and compliant implementation are available on classpath.