Is it possible to add message parameter for constraint violation template message?

I have my custom validator and I want to add some error messages for it. So I have next code:

@Override
public boolean isValid(final String label,
                       final ConstraintValidatorContext constraintValidatorContext) {
     constraintValidatorContext.disableDefaultConstraintViolation();

     if(label.length() > MAX_LENGTH) {
          constraintValidatorContext
                  .buildConstraintViolationWithTemplate("{error.maxLength}")
                  .addConstraintViolation();
          return false;
     }
     ...
}

My message looks like error.maxLength=You have exceeded max length of {0}, so it has parameter of maxLength.

It it possible to add it when building constraint violation?

Yes, you can.

You have to unwrap the ConstraintValidatorContext to an HibernateConstraintValidatorContext with:

HibernateConstraintValidatorContext hibernateConstraintValidatorContext = constraintValidatorContext.unwrap( HibernateConstraintValidatorContext.class );

Then, you can either use:

hibernateConstraintValidatorContext.addMessageParameter("name", value);

(and yours look like a message parameter ({variable}) so it's probably what you have to use - note you need HV 5.4.1.Final to have this method)

or

hibernateConstraintValidatorContext.addExpressionVariable("name", value);

if it's an expression variable (so using Expression Language and something like ${variable})