Is there any way in OpenJPA to get hold of a nested object property via CriteriaBuilder?
Here's a small case.
@Entity
public class X {
private Object Y;
// getters, setters...
}
@Entity
public class Y {
private String Z;
// getters, setters...
}
So, when using CriteriaBuilder, we use X as Root, i.e.:
@PersistenceContext
private EntityManager entityManager;
//.....
Root<X> rootObj = criteriaBuilder.from(X.class);
CriteriaQuery<X> select;
String param1 = X.getY().getZ();
// initializing predicate, default value is TRUE
Predicate predicate1 = criteriaBuilder.isNull(null);
// construct search predicate which fails miserably due to IllegalArgumentExecption
if (X != null) {
predicate1 = criteriaBuilder.and(predicate1, criteriaBuilder.equal(rootObj.<String> get("Y.Z"), param1));
}
Now, my grief is this -> get("Y.Z")
CriteriaBuilder doesn't know to fetch Z reflectively (however it can and will resolve Y). Is there any way to get hold of Z directly from get()?
Apart from using JPQL, I can think of one other method - which I dislike immensely: I suppose I could have exposed Z as an @Transient
property in X (as to prevent OpenJPA from persisting it as a column), but that sounds like a Really Bad Idea: I am essentially flattening out an object graph manually and introduce unneeded garbage inside the entity bean, not counting the time needed to flatten out a complex graph or the error-proness of this (it can go awry in so many ways).
Is there a way to make this work? Any ideas are appreciated.
Heh, the solution is suprisingly simple - and it looks really ugly, but it works.
predicate1 = criteriaBuilder.and(predicate1, criteriaBuilder.equal(rootObj.get("Y").<String> get("Z"), param1));}
I really don't know if there is a more elegant solution to this.