JPA many to many self referencing relation with additional column

Question

I am working with JPA and use Hibernate as a provider to my SQL Server database.

I need a many-to-many self referencing relation that has an additional column or even more additional columns.

That is my current code. I am getting exceptions by Hibernate:

@Entity
public class Person {
  @OneToMany(cascade = CascadeType.ALL, mappedBy = "person", fetch = FetchType.EAGER)
  private Set<Relation> relations;

  @OneToMany(cascade = CascadeType.ALL, mappedBy = "relPerson", fetch = FetchType.EAGER)
  private Set<Relation> inverseRelations;
}

@Entity
public class Relation implements Serializable {
  @Id
  @ManyToOne(cascade = CascadeType.ALL, optional = false, fetch = FetchType.EAGER)
  @PrimaryKeyJoinColumn(name = "PersonID", referencedColumnName = "id")
  private Person person;

  @Id
  @ManyToOne(cascade = CascadeType.ALL, optional = false, fetch = FetchType.EAGER)
  @PrimaryKeyJoinColumn(name = "RelPersonId", referencedColumnName = "id")
  private Person relPerson;
}

During runtime i get an exception from hibernate:

org.hibernate.TransientObjectException: object references an unsaved transient instance

Is there any way to implement this a little bit more intelligent and nicely?? Without getting that exception.

Thanks, ihrigb

Answer 1

If an object not associated with a Hibernate Session , the object will be Transient .

An instance of Relation list may be Transient (Normally, There is no identifier value for that instance) when you save Person .

Here is better way to understand object state.