I have a query using a JOIN and ORDER BY and want to use it within my repository using the Criteria Api.
Here I found, how to wrap such a query into a CriteriaQuery (Link).
CriteriaQuery<Pet> cq = cb.createQuery(Pet.class);
Root<Pet> pet = cq.from(Pet.class);
Join<Pet, Owner> owner = cq.join(Pet_.owners);
cq.select(pet);
cq.orderBy(cb.asc(owner.get(Owner_.lastName),owner.get(Owner_.firstName)));
On the other side, I found some examples to use the Criteria Api in Combination with a JpaRepository (example).
The Problem is that all methods in the repository expect a Specification:
T findOne(Specification<T> spec);
which is always build like this:
public static Specification<PerfTest> statusSetEqual(final Status... statuses) {
return new Specification<PerfTest>() {
@Override
public Predicate toPredicate(Root<PerfTest> root, CriteriaQuery<?> query, CriteriaBuilder cb) {
return cb.not(root.get("status").in((Object[]) statuses));
}
};
}
So at one side I know how to create a CriteriaQuery, and on the other side I need a Specification which is build from a Predicate, and I can not figure out how to parse the CriteriaQuery into a Specification/Predicate.
Try something like this (I assumed pet has many owners):
public static Specification<Pet> ownerNameEqual(String ownerName) {
return new Specification<Pet>() {
@Override
public Predicate toPredicate(Root<Pet> root, CriteriaQuery<?> criteriaQuery, CriteriaBuilder criteriaBuilder) {
Join<Pet, Owner> owners = root.join("owners");
criteriaQuery.orderBy(criteriaBuilder.desc(root.get("id")));
return criteriaBuilder.equal(owners.get("name"), ownerName);
}
};
}
This is just an example to search all pets whose at least one owner has name equal to ownerName
But you could add a method List<Pet> findByOwnersNameOrderByIdDesc(String ownerName);
in your repository instead (as an equivalent to Specification).
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