there is a new add-on which allows using typesafe spring 3 dependency injection for constraint validators. so it's possible to inject other beans (e.g. a validation service, a repository,...) into a constraint validator.
it's similar to the native extval di support. the main difference is that the add-on offers a typesafe alternative. you just have to extend the default-implementation (listed at @Constraint(validatedBy = {...})) and provide the custom implementation as spring bean.