How to declare that primary key is both one-to-one field?

Question

If I write this way

@Id
@OneToOne
@JoinColumn(name="Id")
private Region region;

it says

Composite-id class must implement Serializable: ....InPopulation

I don't want it be composite key, I just want id replaced by Region of appropriate id.

Answer 1

You use the MapsId annotation for that (i have assumed how the @Id is declared):

@Id
private Long id;

@JoinColumn(name = "Id")
@OneToOne
@MapsId
private Region region;