i understand there is a MessageResolver interface. but would it be simpler to the API users if there is a getMessage method that takes a locale like
InvalidConstraint.getMessage( Locale )?

In web application we typically needs to support i18N invalid message.

after looked a JSR 330 implementation (agimatec) in details, it seems a InvalidConstraint is intended to hold an error message for a particular language. it doesn't make sense to hold every language at all. Please disregard my previous suggestion.

Given the MessageResolver is an interface, it means we either have to implement it ourselves or to rely on a provider's implementation. Neither case is good IMHO.

To my understanding, there is no official way to bootstrap a Validator yet. When there is one, please consider to provide an interface to easily create a Validator with a Locale parameter that create a MessageResolver of a particular locale.

Thank you for reading.

Being able to define a local in on my todo list.
The bootstrap API is described here. Have a look!