Spring如何在创建父实体时添加子实体

@Entity
public class ParentEntity {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    // 其他属性

    @OneToMany(mappedBy = "parentEntity", cascade = CascadeType.ALL)
    private List<ChildEntity> childEntities;

    // getter和setter方法
}

@Entity
public class ChildEntity {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    // 其他属性

    @ManyToOne
    @JoinColumn(name = "parent_entity_id")
    private ParentEntity parentEntity;

    // getter和setter方法
}

@Repository
public interface ParentEntityRepository extends JpaRepository<ParentEntity, Long> {
    // 其他方法

    void save(ParentEntity parentEntity);
}

@Repository
public interface ChildEntityRepository extends JpaRepository<ChildEntity, Long> {
    // 其他方法

    void save(ChildEntity childEntity);
}

@Service
public class EntityService {
    @Autowired
    private ParentEntityRepository parentEntityRepository;

    @Autowired
    private ChildEntityRepository childEntityRepository;

    @Transactional
    public void saveParentWithChildEntities(ParentEntity parentEntity) {
        List<ChildEntity> childEntities = parentEntity.getChildEntities();
        parentEntityRepository.save(parentEntity);
        for (ChildEntity childEntity : childEntities) {
            childEntity.setParentEntity(parentEntity);
            childEntityRepository.save(childEntity);
        }
    }
}

@RestController
@RequestMapping("/entities")
public class EntityController {
    @Autowired
    private EntityService entityService;

    @PostMapping
    public void saveParentWithChildEntities(@RequestBody ParentEntity parentEntity) {
        entityService.saveParentWithChildEntities(parentEntity);
    }
}