hibernate - JPA 标准 : downcast root to multiple entity subclasses and filter by the same linked entity natural id

Question

鉴于我有 4 个表:

@Entity
@Inheritance(strategy = InheritanceType.JOINED)
public class SourceEvent {
    @Id
    private Long id;
}

@Entity
@PrimaryKeyJoinColumn(name = "SOURCE_EVENT_ID")
public class PrimaryEvent extends SourceEvent {
    @ManyToOne
    private Account account;
}

@Entity
@PrimaryKeyJoinColumn(name = "SOURCE_EVENT_ID")
public class SecondaryEvent extends SourceEvent {
    @ManyToOne
    private Account account;
}

@Entity
public class Account {
    @Id
    private Long id;

    @NaturalId
    @Column(name = "ACCOUNT_NUMBER", unique = true, nullable = false)
    private long accountNumber;
}

如您所见， SourceEvent是 PrimaryEvent 的父级和 SecondaryEvent并且两个事件都指向 Account .

我想过滤 SourceEvent来自 Account的帐号使用 JPA Criteria API。

我把这个放在一起:

final class Filter {

    private Long accountNumber;

    Specification<SourceEvent> toSpecification() {
        return (Root<SourceEvent> root, CriteriaQuery query, CriteriaBuilder cb) -> {
            return cb.or(
                    cb.equal(cb.treat(root, PrimaryEvent.class).get("account").get("accountNumber"), accountNumber),
                    cb.equal(cb.treat(root, SecondaryEvent.class).get("account").get("accountNumber"), accountNumber)
            );
        };
    }       
}       

我在哪里使用 treat运营商从 SourceEvent 向下转型至 PrimaryEvent和 SecondaryEvent我把两者都相等 Predicate转至 cb.or(...)
当我打电话时 sourceEventRepository.findAll(filter.toSpecification()) ,
而 sourceEventRepository是:

public interface SourceEventRepository extends JpaSpecificationExecutor<SourceEvent>, JpaRepository<SourceEvent, Long> {}

然后我得到以下 Hibernate 生成的 SQL:

...
from
    source_event sourceeven0_ 
inner join
    primary_event sourceeven0_1_ 
        on sourceeven0_.id=sourceeven0_1_.source_event_id 
inner join
    secondary_event sourceeven0_2_ 
        on sourceeven0_.id=sourceeven0_2_.source_event_id 
cross join
    account account1_ 
where
    sourceeven0_1_.account_id=account1_.id 
    and (
        account1_.account_number=123 
        or account1_.account_number=123
    )

什么对我不起作用，因为它不包括 SecondaryEvent s 具有给定的帐号。

如何使它工作？

Answer 1

我们最近遇到了这个问题，并通过更改实体之一的变量名称找到了一种解决方法。

然后我们像向下转型一样强制左外连接。

根据您的用例:

@Entity
@Inheritance(strategy = InheritanceType.JOINED)
public class SourceEvent {
    @Id
    private Long id;
}

@Entity
@PrimaryKeyJoinColumn(name = "SOURCE_EVENT_ID")
public class PrimaryEvent extends SourceEvent {
    @ManyToOne
    private Account account;
}

@Entity
@PrimaryKeyJoinColumn(name = "SOURCE_EVENT_ID")
public class SecondaryEvent extends SourceEvent {
    @ManyToOne
    private Account account1;
}

@Entity
public class Account {
    @Id
    private Long id;

    @NaturalId
    @Column(name = "ACCOUNT_NUMBER", unique = true, nullable = false)
    private long accountNumber;

询问:

final class Filter {

    private Long accountNumber;

    Specification<SourceEvent> toSpecification() {
        return (Root<SourceEvent> root, CriteriaQuery query, CriteriaBuilder cb) -> {
            Root<PrimaryEvent> primaryEventRoot = cb.treat(root, PrimaryEvent.class);
            Join<PrimaryEvent, Account> primaryEvent = primaryEventRoot.join(PrimaryEvent_.account, JoinType.LEFT);

            Root<SecondaryEvent> secondaryEventRoot = cb.treat(root, SecondaryEvent.class);
            Join<SecondaryEvent, Account> secondaryEvent = secondaryEventRoot.join(SecondaryEvent_.account1, , JoinType.LEFT);
            return cb.or(
                    cb.equal(primaryEvent.get("accountNumber"), accountNumber),
                    cb.equal(secondaryEvent.get("accountNumber"), accountNumber)
            );
        };
    }       
}