Bean Validation message interpolation with array constraint parameter used as variable in message

Question

Is it possible to join the int array arguments in javax.validation error message interpolation?

I want to validate a string for different possible lengths and I started implementing a custom constraint:

@Constraint(validatedBy = {BarcodeValidator.class})
public @interface Barcode {
String message() default "{validation.Barcode.message}";
  int[] lengths();
}

The validator:

public class BarcodeValidator implements ConstraintValidator<Barcode, String> {

  private List<Integer> lengths;

  @Override
  public void initialize(Barcode barcode) {
    lengths = new ArrayList<>(barcode.lengths().length);
    for (int l : barcode.lengths()) lengths.add(l);
  }

  @Override
  public boolean isValid(String value, ConstraintValidatorContext context) {
    return value != null && lengths.contains(value.length());
  }
}

I would like a custom message for it like: The barcode must be 12/23/45 character long!

I have figured out I can use the annotation parameters in the message, so I would like to do something like:

validation.Barcode.message = The barcode must be ${'/'.join(lengths)} character long!

Is something like that possible or should I do it in some other way?

(P.S.: My first question here on SO.)

Answer 1

Eventually I found a solution.
Validator class:

public class BarcodeValidator implements ConstraintValidator<Barcode, String> {

  private List<Integer> lengths;

  @Override
  public void initialize(Barcode barcode) {
    lengths = new ArrayList<>(barcode.lengths().length);
    for (int l : barcode.lengths()) lengths.add(l);
  }

  @Override
  public boolean isValid(String value, ConstraintValidatorContext context) {
    context.unwrap(HibernateConstraintValidatorContext.class).addExpressionVariable("joinedLengths", String.join(" / ", lengths));
    return value != null && lengths.contains(value.length());
  }
}

*.properties:

validation.Barcode.message = The barcode must be ${joinedLengths} character long!

Also tried naming the parameter lengths, but that did not work - it is probably bound to the type int[].