Embedded IDs Best Practice (MappedEntity vs ID) #2957

angus-clark · 2024-05-23T21:19:59Z

angus-clark
May 23, 2024

When creating an embedded id for a composite primary key should the fields that make up the embedded id be the raw values such as an Integer or UUID? Or should they be the full object/mapped entity in which they represent?

For example, say we have a database setup consisting of an "account" table and a "club" table and there is a many to many relationship exists between theses two tables. Therefore we have a third table "club_member" which connects accounts and clubs as represented below.

create table club_member
(
    club_id      uuid references club (id) on delete cascade not null,
    account_id   uuid references account (id) on delete cascade   not null,
    primary key (book_club_id, account_id)
);

So the question is what should the Embedded Id for this table look like out of the two options below?

Option 1:

@Serdeable
@Embeddable
public class ClubMemberId {

    @MappedProperty("account_id")
    private UUID accountId;

    @MappedProperty("club_id")
    private UUID clubId;
}

Option 2:

@Serdeable
@Embeddable
public class ClubMemberId {

    @MappedProperty("account_id")
    private Account account;

    @MappedProperty("club_id")
    private Club club;
}