Hibernate mapping a composite key with null values

Question

With Hibernate, can you create a composite ID where one of the columns you are mapping to the ID can have null values?

This is to deal with a legacy table that has a unique key which can have null values but no primary key.

I realise that I could just add a new primary key column to the table, but I'm wondering if there's any way to avoid doing this.

Answer 1

No. Primary keys can not be null.

Answer 2

You wont get error but Hibernate wont be able to map those rows with NULL value for composite column to your Entity. That means you get entity with NULL values in result.