将@EntityGraph与JPA构造函数表达式一起使用

Question

我有一个使用构造函数表达式的查询。在大多数情况下，它是工作的，但是我想减少数据库上的查询数量。所以我尝试了FETCH和@EntityGgraph，但是我得到了

org.springframework.dao.InvalidDataAccessResourceUsageException:查询指定的联接提取，但提取关联的所有者不在选择列表中[FromElement{explicit，不是集合联接，提取联接，提取非惰性。。。

我尝试删除FETCH，只使用JOIN来解决问题，但它不执行FETCH操作。

Hibernate/JPA是否允许或可能这样做？

代码方面看起来有点像

@Query("select new example.BillingTargetAndStudent(bt,s) from Student s, BillingTarget bt where s.id = bt.targetID and bt.account.status = :accountStatus and bt.account.organization = :organization")
Stream<BillingTargetAndStudent> streamAllByOrganizationAndStatusForStudentList(Organization organization, AccountStatus accountStatus);

我要做的是在同一查询中获取bt.account和s.user.attributes。bt.account并不难解决，但是s.user.attributes不可能与构造函数表达式一起使用，因为它是一个集合

Answer 1

我最终做的是使用流

default Stream<BillingTargetAndStudent> streamAllByOrganizationAndStatusForStudentList(Organization organization, AccountStatus accountStatus) {

    return streamAllByOrganizationAndStatusForStudentList0(organization, accountStatus)
        .map(o -> new BillingTargetAndStudent((BillingTarget) o[0], (Student) o[1]));
}

@Query("select bt, s from Student s join fetch s.user u join fetch u.attributes, BillingTarget bt join fetch bt.account a where s.id = bt.targetID and bt.account.status = :accountStatus and bt.account.organization = :organization")
Stream<Object[]> streamAllByOrganizationAndStatusForStudentList0(Organization organization, AccountStatus accountStatus);

我可以通过输入一个@EntityGraph

@EntityGraph("Student.forStudentList")
@Query("select bt, s from Student s, BillingTarget bt left join fetch bt.billingContractTargets bct join fetch bt.account a where s.id = bt.targetID and bt.account.status = :accountStatus and bt.account.organization = :organization")
Stream<Object[]> streamAllByOrganizationAndStatusForStudentList0(Organization organization, AccountStatus accountStatus);

@NamedEntityGraph(
    name = "Student.forStudentList",
    attributeNodes = {
        @NamedAttributeNode("schedules"),
        @NamedAttributeNode(value = "user", subgraph = "user.attributes"),
    },
    subgraphs = {
        @NamedSubgraph(name = "user.attributes",
            attributeNodes = {@NamedAttributeNode("attributes")})
    }
)

但我仅限于一个，它必须是存储库的实体。我不能说

@EntityGraph("BillingTarget.forStudentList")
@EntityGraph("Student.forStudentList")