When having two entities with multiple to-many associations between them (say entities User and Address and two associations User#primaryAddresses() and User#secondaryAddresses()), the same join table name ("User_Address") will be used, causing a constraint violation exception upon insertion for one of the association types, as the column(s) of the other type will be null in that case.

So it'd be nice if automatically either two join tables with unique names were used or at least an error was issued during bootstrap, requesting the user to explicitly specific names via @JoinTable.

It might technically also be possible to actually use one join table only, if the columns where nullable. I don't think that's a desirable mapping, though.