I am a Hibernate newbie, and trying to see whether it is possible to use Criteria projections to return a collection of one-to-many associated objects, and cannot get the data. My entity mapping is like below:

Class A <n----1> Class B <1----n> Class C

I am using

Criteria criteria = createCriteria(A.class).
.createAlias("B", "B")
.createAlias("B.C", "C")
.setProjection(Projections.projectionList().
.add(Projections.property("B.f1")
.add(Projections.Property("B.C");
List<Object[]>rows = criteria.list();

I am expecitng the rows[*].[0] is f1 value, and rows[*].[1] is List<C>, a collection of C objects. But I cannot get back any rows[*].[1].

Any suggestions?

Thanks.

If ClassB contains ClassC, and the mapping is defined, you only need to select ClassB. Instances of ClassC will be populated based on the mapping. Is that what you are trying to do?

LinHib,

Thanks for the reply. B defines a one-to-many mapping to C (which is another entity). The reason I do not want to pull up B fully is because B has many many other fields/collections which we do not need, and it takes a long time to fill these values if we put B in the result projection (it seems to try to compute all B properties/collections then).

In our situation, we want to extract all (a large number of) the As in database. Since we only need A.B.f1 (a string value) and A.B.C (List of C objects), we want to know how we can retrieve and fill just these two properties to improve performance.

Is there anyway we can achieve this?

If you use lazy loading for B (by setting default-lazy="true" in the hibernate-mapping), and do not use lazy (by setting lazy="false") for the association to C, you can build B with only C populated (without loading any other associated entities).

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