The other way to express this is with generics,

class Entity<D: Int?>(val id: D)

and then keep the nullability in the type throughout the code.

how do I create a new

Entity

in this case? the

id

has to be

null

for hibernate to generate it, but with

val id: D

I cannot assign

null

to

id

D

can be nullable, right?

Oh, now I see what you meant. Thanks 🙂