JPA Criteria：将根向下转换为多个实体子类，并按相同的链接实体自然 id 进行过滤

Question

鉴于我有 4 张表：

@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;
}

正如您所看到的，SourceEvent是 和 的父级，PrimaryEvent并且SecondaryEvent两个事件都指向Account。

我想使用 JPA Criteria API 按 的帐号过滤SourceEvents 。Account

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)
            );
        };
    }       
}       

我使用运算符从totreat向下转换为and我将两个 equals s都放在SourceEventPrimaryEventSecondaryEventPredicatecb.or(...)

当我打电话时sourceEventRepository.findAll(filter.toSpecification())，而是sourceEventRepository：

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

然后我得到以下由 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，因为它不包含SecondaryEvent给定帐号的 s 。

如何让它发挥作用？

Answer 1

我们最近遇到了这个问题，并通过更改其中一个实体的变量名称找到了解决方法。

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)
            );
        };
    }       
}