Java 带规格的弹簧护套总和(列)
我有一个实体,说:Java 带规格的弹簧护套总和(列),java,spring,specifications,Java,Spring,Specifications,我有一个实体,说: class MyEntity { Long id; String attr1; String attr2; String attr3; String attr4; Double attr5; } 我使用规范查询按属性过滤的结果,如: class MySpecification implements Specification<MyEntity> { private String attr1; pri
class MyEntity {
Long id;
String attr1;
String attr2;
String attr3;
String attr4;
Double attr5;
}
我使用规范
查询按属性过滤的结果,如:
class MySpecification implements Specification<MyEntity> {
private String attr1;
private String attr2;
private String attr3;
private String attr4;
@Override
public Predicate toPredicate(Root<MyEntity> root, CriteriaQuery<?> query, CriteriaBuilder criteriaBuilder) {
List<Predicate> restriction = new ArrayList<>();
if (!StringUtils.isEmpty(attr1)) {
restriction.add(criteriaBuilder.equal(root.get("attr1"), attr1));
}
if (!StringUtils.isEmpty(attr2)) {
restriction.add(criteriaBuilder.equal(root.get("attr2"), attr2));
}
// And so on
Predicate predicate = criteriaBuilder.disjunction();
predicate.getExpressions().add(criteriaBuilder.and(restriction.toArray(new Predicate[restriction.size()])));
return predicate;
}
}
类MySpecification实现了规范{
私有字符串attr1;
私有字符串属性2;
私有字符串属性3;
私有字符串属性4;
@凌驾
公共谓词toPredicate(根根、CriteriaQuery查询、CriteriaBuilder CriteriaBuilder){
列表限制=新建ArrayList();
如果(!StringUtils.isEmpty(attr1)){
add(criteriaBuilder.equal(root.get(“attr1”),attr1));
}
如果(!StringUtils.isEmpty(attr2)){
add(criteriaBuilder.equal(root.get(“attr2”),attr2));
}
//等等
谓词=criteriaBuilder.disconction();
predicate.getExpressions().add(criteriaBuilder.and(restriction.toArray)(新谓词[restriction.size()]);
返回谓词;
}
}
现在我想通过规范
获得attr5
的总和,我该怎么做
感谢您的高级指导。经过研究,以下是解决方案: 创建一个接口:
interface MyRepositoryCustom {
<S extends Number> S sum(Specification<MyEntity> spec, Class<S> resultType, String fieldName);
}
@Repository
class MyRepositoryCustomImpl implements MyRepositoryCustom {
@Autowired
private EntityManager entityManager;
@Override
public <S extends Number> S sum(Specification<MyEntity> spec, Class<S> resultType, String fieldName) {
CriteriaBuilder builder = entityManager.getCriteriaBuilder();
CriteriaQuery<S> query = builder.createQuery(resultType);
Root<MyEntity> root = applySpecificationToCriteria(spec, query);
query.select(builder.sum(root.get(fieldName).as(resultType)));
TypedQuery<S> typedQuery = entityManager.createQuery(query);
return typedQuery.getSingleResult();
}
protected <S> Root<MyEntity> applySpecificationToCriteria(Specification<MyEntity> spec, CriteriaQuery<S> query) {
Root<MyEntity> root = query.from(MyEntity.class);
if (spec == null) {
return root;
}
CriteriaBuilder builder = entityManager.getCriteriaBuilder();
Predicate predicate = spec.toPredicate(root, query, builder);
if (predicate != null) {
query.where(predicate);
}
return root;
}
}
@Repository
interface MyEntityRepository extends JpaRepository<MyEntity, Long>, MyRepositoryCustom {
}