I think this may not be possible with the current JPA annotations, but just wanted to confirm.

I have a ManyToOne Child->Parent relationship that is not via a foreign key but instead via a shared identifier that happens to be unique on the Parent.

1) Is there any way to map this using the JPA annotations?

2) If not, is it possible to write some clean HQL to populate the Child object with the parent? e.g. I don't think a fetch join is applicable because the Child's ref would not be mapped. I guess I could use a projection and the constructor syntax...

Just wondering if there is a clean solution as this seems like a simple case.


thanks,
Pat Niemeyer

@JoinColumn(name = "MY_FK_COLUMN", referencedColumnName = "MY_UNIQUE_NONPK_COLUMN")

Thanks for the response.

I had tried this earlier but was getting errors that I don't understand.

e.g. if Parent and Child each have a column called parentId:

@ManyToOne
@JoinColumn(name = "parentId", referencedColumnName = "parentId")
private Parent parent;

I then get a ClassCastException for the Parent class at org.hibernate.type.ManyToOneType.hydrate()

If I leave off the referencedColumnName. I get a different query error - Fail to convert to internal representation.

I have the Manning book and have been looking around elsewhere but cannot find any good documentation on the JoinColumn annotation or how to apply it.


Pat

You need to make the Parent class Serializable - that's why you're getting a class cast exception.

From the hibernate annotation documentation: