One of the possible solutions is to create custom UniqueKey constraint (and corresponding validator); and to look-up the existing records in database, provide an instance of EntityManager (or Hibernate Session )to UniqueKeyValidator .
One possibility is to annotate the field as @NaturalId.
I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.