How to map unidirectional @OneToMany with embeddedId in Hibernate

Issue

• We are trying to map two entities, with a @OneToMany association between two entities.
• Class has a composite primary key, so we made an @EmbeddedId inside it.
• How can we map in the right way a @OneToMany relationship with CascadeType=ALL, in order to make entityManager.persist(object) and entityManager.merge(object) working correctly? How to map these relationships in the right way, in order to make them work with persist and merge methods of entityManager.
• Is it not possible to make it work with a unidirectional mapping? @OneToMany on Customer object, but without @ManyToOne in Product?