I am putting this into the next release. There is already work in this area (Hibernate, JSR etc)... so we will need to watch these to see the developments.

Its ended up to be a similar design to Hibernate Validation. That is, you annotate your properties with @NotNull, @Length(min=5,max=20) etc - these annotations I would expect to become standardised by the JSR in the future.

I am pretty conscience of the potential performance penalty and cascading validation (cascading like save and delete can). I have ended up putting the validation inside Ebean itself rather than an external framework (bypassing reflection and building fast meta data about what validation needs to occur when).

All in all pretty good stuff...