Pobieranie lokalnej wiadomości z pliku properties przez wyjątek ConstraintViolationException

@Override
public void registerUser(
        @Valid RegisterDTO registerDTO
) {

@NotEmpty
@Pattern(regexp = "[a-zA-Z0-9_-]{6,36}")
private String username;

@ExceptionHandler(ConstraintViolationException.class)
@ResponseStatus(HttpStatus.BAD_REQUEST)
public ValidationErrorDTO processValidationError(ConstraintViolationException ex) {
    ValidationErrorDTO validationErrorDTO = new ValidationErrorDTO();

    Set<ConstraintViolation<?>> set =  ex.getConstraintViolations();

    for (Iterator<ConstraintViolation<?>> iterator = set.iterator();iterator.hasNext(); ) {
        ConstraintViolation<?> next =  iterator.next();

        validationErrorDTO.getFieldErrors()
                .add(new ErrorFieldDTO(((PathImpl)next.getPropertyPath()).getLeafNode().getName(),
                        next.getMessage()));
    }

    return validationErrorDTO;
}

NotEmpty.registerDTO.username=This field is required.
Pattern.registerDTO.username=Please enter at least 6 characters(max. 36 characters). Only letters, numbers and special characters '_' and '-'.