JPA @EmbeddedId: How to update part of a composite primary key?

Question

I have a many-to-many relationship where the link table has an additional property. Hence the link table is represented by an entity class too and called Composition

Answer 1

Why not just change the primary key of Composition to be a UID which is auto-generated? Then the users could change the two references to the entities being joined without having to delete/re-create the Composition entity. Optimistic locking would then be maintained.

EDIT: For example:

@Entity
@Table(name = "COMPOSITION")
public class Composition {

    @Id
    @Column(name = "ID")
    private Long id;   // Auto-generate using preferred method

    @ManyToOne(fetch = FetchType.LAZY, optional = false)
    @JoinColumn( .... as appropriate .... )
    private FirstEntity firstEntity;

    @ManyToOne(fetch = FetchType.LAZY, optional = false)
    @JoinColumn( .... as appropriate .... )
    private SecondEntity secondEntity;

....