EclipseLink/JPA: Multiple @DiscriminatorColumn annotations for Entity

Question

I'm looking for a way in EclipseLink to have two @DiscriminatorColumns on the same entity

My PostreSQL DB table is:

Dictionary
{
  id,
  object_type,
  attribute_type,
  translation
}

And classes are:

@Entity
@Table(name = "dictionary")
@Inheritance(strategy=InheritanceType.SINGLE_TABLE)
@DiscriminatorColumn(name="object_type", 
                     discriminatorType=DiscriminatorType.INTEGER)
public class DictionaryRow implements Serializable;

@Entity
@DiscriminatorValue("0")
@DiscriminatorColumn(name="info_type", 
                     discriminatorType=DiscriminatorType.INTEGER)
@Inheritance(strategy=InheritanceType.SINGLE_TABLE)
public class DictionaryAttribute extends DictionaryRow;

@Entity
@DiscriminatorValue("1")
public class DictionaryAttributeName extends DictionaryAttribute;

What I'm trying to achieve is that when I call for DictionaryAttributeName it will be resolved to SQL like:

select * from DICTIONARY where info_type = 1 and object_type = 0

But actually, it takes the DiscriminatorColumn from the DictionaryRow class, and DiscriminatorValue from the DictionaryAttributeName, resulting in the totally wrong SQL:

select * from DICTIONARY where object_type = 1

Is there a solution for this issue?

Thanks

Answer 1

According to the JPA 2.0 specification, this is not possible:

11.1.10 DiscriminatorColumn Annotation

For the SINGLE_TABLE mapping strategy, and typically also for the JOINED strategy, the persistence provider will use a type discriminator column. The DiscriminatorColumn annotation is used to define the discriminator column for the SINGLE_TABLE and JOINED inheritance mapping strategies.

The strategy and the discriminator column are only specified in the root of an entity class hierarchy or subhierarchy in which a different inheritance strategy is applied.

References

• JPA 2.0 Specification
  • Section 11.1.10 "DiscriminatorColumn Annotation"