JPA 潜在的同步问题

Question

在我的寄宿类里，我有

@OneToMany(cascade = CascadeType.ALL, fetch = FetchType.LAZY, mappedBy = "lodger", orphanRemoval=true)
//  @JsonBackReference
private List<RoomPayment> roomPaymentList;

在我的 RoomPayment 类中有

@ManyToOne(fetch = FetchType.LAZY)
@JoinColumn(name = "lodger_id")
private Lodger lodger;

其实我有

@Override
public Long save(RoomPaymentDto roomPaymentDto) {

    RoomPayment roomPayment;

    if (roomPaymentDto.getRoomPaymentId() != null) {
        roomPayment = repository.findOne(roomPaymentDto.getRoomPaymentId());
    } else {
        roomPayment = new RoomPayment();
    }

    MapperFactory mapperFactory = new DefaultMapperFactory.Builder().build();
    mapperFactory.classMap(RoomPayment.class, RoomPaymentDto.class).byDefault().register();

    MapperFacade mapper = mapperFactory.getMapperFacade();

    mapper.map(roomPaymentDto, roomPayment);

    repository.save(roomPayment);

    return roomPayment.getRoomPayementId();
}

在这个方法中，我需要获取 Lodger 并将其分配给 roomPayment 吗？

Answer 1

不，当然，如果 dto 包含正确的 Lodger。

重点是没有从 RoomPayment 到关联的 Lodger 的级联，这意味着当您保存 roomPayment 时，Hibernate 不会提示分离的对象。

Hibernate 只会从 lodger 实例中获取 id，它将用于维护关联(因为 RoomPayment 是关联的所有者)。