Spring-Data Jpa Inheritance: Keeping Entity Id's in Children Entity

epsilonmajorquezero :

I'm dealing with a couple of Entities with Tree like structures that were getting more complicated so I decided to create an abstract class for it so code was a bit more mainainable:

@Entity
@Inheritance(strategy = InheritanceType.TABLE_PER_CLASS)
public abstract class TreeStructure<T extends TreeStructure>
{
    @ManyToOne
    protected  T parent;

    @OneToMany(mappedBy = "parent", fetch = FetchType.LAZY)
    protected Set<T> children = new HashSet<>();
    //...

Then I have two Entities which extend it:

@Entity(name = "TreeStructureOne")
public class TreeStructureOne extends TreeStructure<TreeStructureOne>
{
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    @JsonProperty("TreeStructureOne_id")
    private long id;

And I basically want the database to be completely unaware of this TreeStructure abstraction and save all of the fields in each Entities tableand expected InheritanceType.TABLE_PER_CLASS to deal with that. But it seems I need to define the Id in the TreeStructure Entity at least or I get:

Invocation of init method failed; nested exception is org.hibernate.AnnotationException: No identifier specified for entity: TreeStructure

And I don't want to add an ID into the abstract class since this makes three tables in the database called: HT_TREE_STRUCTURE, HT_TREE_STRUCTURE_ONE and HT_TREE_STRUCTURE_TWO with one field ID each one.

Is there any solution to that?

michaeak :

Since TreeStructure is not an @Entity use only @MappedSuperclass

@MappedSuperclass
public abstract class TreeStructure<T extends TreeStructure> {

instead of @Entity and @Inheritance for the parent class.

You can find @MappedSuperclass in the Oracle JEE API documentation.