具有复合ID的JPA可嵌入实体

Question

I have a rather simple schema, I think, but I can't find the right way of mapping it.

@Entity
class Satellite {
   @Id
   private int id;
   // stuff
   @ElementCollection @OrderBy(value = "orbit asc")
   private List<DataModel> dataModel;
}

the embeddable class is the following:

class DataModel {
    private int orbit;
    private int data;
}

the problem is, orbit should be unique for each satellite. In my mind the table representing datamodel has a composite primary key composed of the satellite id and orbit. But I can't find the right way of mapping it. If I declare the DataModel as a plain entity, I have to add a satellite field mapped manytoone and a composite primary key that include satellite and orbit, but it does not works (stack overflow!!).

I'm using hibernate as persistence provider.

Answer 1

If I declare the DataModel as a plain entity, I have to add a satellite field mapped manytoone and a composite primary key that include satellite and orbit.

On the db level you'd have to do that anyways, ie the table containing the DataModel would need a foreign key to the satellite. In that case I don't see a reason not to make DataModel an entity:

@IdClass( DMKeyClass.class )
@Entity
class DataModel {
  @Id
  private Satellite sat;
  @Id
  private int orbit;
  private int data;
}

class DMKeyClass {
  public int sat;
  public int orbit;
}