java - JPA/Hibernate "Composite-id class does not override equals()"

Question

I'm using JPA and getting the following warning. I've researched this, and understand why I need to override it and how Hibernate uses these methods. I still have a question though:

Exception:

Composite-id class does not override equals()

Question:

Why does Hibernate only care about classes that don't have composite IDs? Does it by default compare on the @Id field if there is only one present, or is there something more complex going on here?

Answer 1

Because when entities don't have a composite ID, they have a single one, of one of the basic supported types (Integer, Long, String, etc.), and those classes already have a well-defined equals() (and hashCode()) method.