If we want to include a type-safe approach later on, we might do it like this:

* Pull ConstraintValidator#initialize() up into a new interface Initializeable

* Change @CrossParameterConstraint#validatedBy() to return Class<? extends Initializable<?, ?>>. AFAICS that shouldn't be a problem for existing constraint definitions, BV providers need of course to adapt. Short tests I did looked good.

--Gunnar