I have seen references to the fact that rules-based validation may be added to Spring. (Rob Harrop's book ProSpring mentions this for one). Does this exist yet?
Specifically, we are looking to improve the validation for our domain models. Some of the business rules are relatively complex, well... they really are not all that complex, but they require input data from multiple objects not just the object that is passed to the standard Validator.
Also, it seems to me that validation should be able to be defined against an attribute, not just the class. As a simple example, I'd like to specify that a specific attribute is mandatory, possibly conditionally mandatory depending on the value of an attribute in a different model. I don't really want to bury this code into a single Validator class along with all of the other attribute validation rules on that class.
I would appreciate any thoughts or options for domain model validation.