无法为实体设置多对一，具有双重持久性

Question

@Entity
public class Room {
@Id
@GeneratedValue(strategy = GenerationType.AUTO)
private Long id;
@OneToMany(mappedBy = "Room", fetch = FetchType.EAGER)
private List<SponsorStart> sponsorsStart = new ArrayList<>();
//getters setters

@Entity
@Table(name = "sponsors_start")
public class SponsorStart {
@Id
@GeneratedValue(strategy = GenerationType.AUTO)
private Long id;
@Column
private String username;
@ManyToOne(cascade=CascadeType.ALL)
@JoinColumn(name = "room_id")
private Room Room;

@Repository
public interface RoomRepository extends CrudRepository<Room, Long> {
}
From RoomServiceImpl save:
@Override
public Room saveRoom(Room Room) {
return roomRepository.save(Room);
}

我的行为顺序是什么?

1. List<SponsorStart> sponsorStarts = new ArrayList<>();
2. Room room = new Room();
3. giveRoom.setSponsorsStart(sponsorStarts); //set list of sponsors form p.1
4. giveRoomService.saveRoom(room); //save room

sponsors_start_db为空。我尝试先保存每个sposorStart从列表中，但他们在room_id列中保存null。对不起，我知道这应该是简单的，但在我的情况下，我做错了。谢谢!

Answer 1

1. 您应该将cascade=CascadeType.ALL移动到您的协会的@OneToMany一侧:

@OneToMany(mappedBy = "Room", fetch = FetchType.EAGER, cascade=CascadeType.ALL)
private List<SponsorStart> sponsorsStart = new ArrayList<>();

2. 你应该同步双向关联的两边:

List<SponsorStart> sponsorStarts = new ArrayList<>();
SponsorStart sponsorStart1 = new SponsorStart();
sponsorStarts.add(sponsorStart1);
// ...
Room room = new Room();
// sync both side of the association
sponsorStart1.setRoom(room);
room.setSponsorsStart(sponsorStarts); //set list of sponsors form p.1
room.saveRoom(room); //save room

请参阅hibernate文档的这一部分。