Is it possible to retrieve @IdClass from Metamodel?

Hibernate ORM
1

I have some entities that have a composite primary key and are annotated with:

@IdClass(PrimaryKeyClass.class)

This is how I currently retrieve the @IdClass class:

EntityType<?> entityType = entityManager.getMetamodel().entity(entityClass);
Class<?> result = entityType.getJavaType().getAnnotation(IdClass.class).value();

My question is if it possible to retrieve @IdClass of given entity directly from the Metamodel. I seem to be able to retrieve the individual fields that are part of the primary key and annotated with @Id, but not the PK class.

Alternatively, do you see any problem with my current approach?

Cheers

2

entityType.getIdType().getJavaType() should return what you are looking for.

3

Thank you for response.

This is what I initially tried, but I receive null for entityType.getIdType().

Please note that I did not use annotate the field with @EmbeddedId, but added the annotation @IdClass(…) on the entity class and kept the fields that compose the key in the class. With the embeddable approach it would have worked.

4

Ok, in that case you can access this through entityType.getAttribute("id").getBindableJavaType()

5

That also does not work for me. “id” is not part of the attributes of the entity type, which makes sense to me since it is not a field in the entity class.

Just to be sure, this is my entity:

public class PrimaryKeyClass implements Serializable {
private Long first;
private Short second;

// + getters/setters
}

@Entity
@IdClass(PrimaryKeyClass.class)
@MappedSuperclass
public class MyEntity implements Serializable {
@Id
private Long first;

@Id
private Short second;

// + other fields/getters/setters
}

Also, it is not really important because of my previous point, but entityType.getAttribute("id") returns an Attribute that does not implement getBindableJavaType(). Available methods: getDeclaringType(), getJavaMember(), getJavaType(), getName(), getPersistentAttributeType(), isAssociation(), isCollection().

6

We treat id as a “special” attribute name in case you don’t have an attribute named like that. You could also use the {id} name instead if you fancy that more.

Also, it is not really important because of my previous point, but entityType.getAttribute("id") returns an Attribute that does not implement getBindableJavaType().

Well, I don’t have the code in front of me, so I’m just giving you advice based on memory. getJavaType() should return what you are looking for then though.

7

You could also use the {id} name instead if you fancy that more.

I’m trying to obtain the @IdClass containing these @Id annotated fields. These would be the PK of entity, but not an actual field in the class.

I debugged the Hibernate code. And my findings these thing happen in the following order:

(in org.hibernate.cfg.AnnotationBinder)

1/ the annotation @IdClass is read
2/ the @Id attributes are saved
3/ boolean isIdClass is calculated
4/ … (the @IdClass type is not saved)

Therefore I question whether it is possible to return in any way the type of the PK since Hibernate seems to work only with this set of fields annotated with @Id and not the Java type of the PK (the manual here seems to suggest the same: HIBERNATE - Relational Persistence for Idiomatic Java)

8

Which Hibernate version are you using? Some of the things I talk about here depend on that.

You could also use the {id} name instead if you fancy that more.

Sorry for the confusion. First of all, the {id} name is actually just an internal name used for the runtime mapping model, not for the JPA model. I wrongly assumed this was accessible in the JPA metamodel as well.

Since Hibernate 6, there are JPA metamodel extensions which you can use to query this information.

((IdentifiableDomainType<?>) entityManager.getMetamodel().entity(entityClass))
  .getIdentifierDescriptor()
  .getSqmPathType()
  .getJavaType()

Will give you that information. If you don’t want to use that or are still stuck on Hibernate 5, it’s probably best to keep using what you have right now.

1 Like
9

Yes, I have Hibernate version 5.4.22.

Then that makes sense. Thanks for the help.