规范中的JpaSpecificationExecutor JOIN + ORDER BY [英] JpaSpecificationExecutor JOIN + ORDER BY in Specification
问题描述
我有一个使用JOIN和ORDER BY的查询,想要使用Criteria Api在我的存储库中使用它。
I have a query using a JOIN and ORDER BY and want to use it within my repository using the Criteria Api.
在这里我发现,如何包装这样的查询CriteriaQuery(链接)。
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)));
另一方面,我发现一些例子将Criteria Api与JpaRepository结合使用(< a href =http://www.cubrid.org/wiki_ngrinder/entry/how-to-create-dynamic-queries-in-springdata =nofollow>示例)。
On the other side, I found some examples to use the Criteria Api in Combination with a JpaRepository (example).
问题是存储库中的所有方法都需要一个规范:
The Problem is that all methods in the repository expect a Specification:
T findOne(Specification<T> spec);
总是这样构建:
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));
}
};
}
所以在一方面我知道如何创建CriteriaQuery,另一方面,我需要一个基于谓词构建的规范,我无法弄清楚如何将CriteriaQuery解析为规范/谓词。
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.
推荐答案
尝试这样的事情(我假设宠物有很多所有者):
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);
}
};
}
这只是搜索至少一位拥有者姓名的所有宠物的示例等于 ownerName
This is just an example to search all pets whose at least one owner has name equal to ownerName
但是你可以添加一个方法 List< Pet> findByOwnersNameOrderByIdDesc(String ownerName);
在您的存储库中(相当于规范)。
But you could add a method List<Pet> findByOwnersNameOrderByIdDesc(String ownerName);
in your repository instead (as an equivalent to Specification).
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