I have the following constellation

Unit
Section extends Unit
Chapter extends Unit

Unit has two methods getParent() and getChildren() that are mapped via a ManyToOne/OnToMany

Now, if a Section is parent to a Chapter, what should the getParent() call return? I expected, that the inheritance is respected with this mapping, but the call returns a Unit-Object.

This, of course is consistent with the targetEntity determined by the getParent():Unit-Call - but if breaks the Type-Scheme. Is there a way around this? Casting, of course, does not work, as the parent is only fetched with the data for Unit and misses all Section-Fields....

thx for the help!
stf

If parent is actually fetched, you should be able to down cast.
But it seems your domain model is broken if you need to cast.

Is the model really broken? In unit, the model says, that

getParent():Unit returns Unit

and getChildren():List<Unit> also returns Units, and not the subclasses.

Therefore, only Unit appears as target-entity in the joins. getParent() and getChildren is not overwritten in the subclasses. Is this domainmodel already wrong?

How does hibernate determine the right classes for the fetched entities in this case?

As I've seen, hibernate joins to all possible joined-tables. Does it then look which columns are filled to determine which of the joined-tables had a hit?


thx for the help!
stf

Hibernate returns you the correct subentity by outer-joining all the tables and finding which columns are not null. Of course it can't when the association is lazy (the proxy is of the super entity type).