java - Spring Data JPA - 如何通过 child ID 获取 parent ？

Question

我有带有@ManyToMany 注释的父实体和子实体:

@Entity
@Table(name = "parent")
public class Parent {

    @Id
    @GenericGenerator(name = "uuid-gen", strategy = "uuid2")
    @GeneratedValue(generator = "uuid-gen",strategy=GenerationType.IDENTITY)
    private String id;

    @ManyToMany(fetch = FetchType.LAZY)
    @JoinTable(name = "parents_childs",
        joinColumns = {@JoinColumn(name = "parent_id", nullable = false, updatable = false)},
        inverseJoinColumns = {@JoinColumn(name = "child_id", nullable = false, updatable = false)})
    private List<Child> childs;
}

和子实体:

@Entity
@Table(name="child")
public class Child {

    @Id
    @GenericGenerator(name = "uuid-gen", strategy = "uuid2")
    @GeneratedValue(generator = "uuid-gen",strategy=GenerationType.IDENTITY)
    private String id;

}

我的任务是找到所有包含具有特定 id 的 Child 的 Parents。我尝试以这种方式在我的存储库中执行此操作:

@Query("select p from Parent p where p.childs.id = :childId and --some other conditions--")
@RestResource(path = "findByChildId")
Page<Visit> findByChild(@Param("childId") final String childId, final Pageable pageable);

异常(exception):

java.lang.IllegalArgumentException: org.hibernate.QueryException: illegal attempt to dereference collection [parent0_.id.childs] with element property reference [id] [select p from Parent p where p.childs.id = :childId and --some other conditions--]

我知道可以解决将 _ 添加到方法名称，如 findByChilds_Id (如 here )，但我找不到如何在 @Query注解。

如何用JPQL来写？

Answer 1

我找到了解决方案:

@Query("select p from Parent p join p.childs c where c.id = : childId and  --some other conditions--")