java - 如何在 hibernate 中正确设置双向关联@OneToMany

Question

我想创建双向@OneToMany 连接，但我认为我误解了一些东西。我有用户实体:

public class User {

    @Id
    @GeneratedValue(strategy = AUTO)
    private Long id;
    private String name;
    private String password;

    @ManyToOne(fetch = FetchType.EAGER, cascade = CascadeType.ALL)
    private Team team;
}

和团队实体:

public class Team {

    @Id
    @GeneratedValue(strategy= AUTO)
    private Long id;

    private String name;

    @OneToMany(cascade = CascadeType.ALL,
            fetch = FetchType.EAGER,
            mappedBy = "team")
    private Set<User> users = new HashSet<>();
}

用户只能拥有一个团队，但团队可以拥有多个用户。我尝试测试一下:

 User user = new User();
        Team team = new Team();
        team.setName("test_team");
        user.setTeam(team);
        userRepository.save(user);

userRepository.findAll() 返回我:

[{"id":1,"name":null,"password":null,"team":{"id":2,"name":"test_team","users":[]}]

teamRepository.findAll() 返回我:

[{"id":2,"name":"test_team","users":[]}]

为什么会发生这种情况？我想创建双向连接，但团队实体似乎不了解任何用户。

如何创建一个连接，如果我添加用户实体或更新用户的团队，团队实体也会更新？

Answer 1

您在父端缺少 @JoinColumn:

@JoinColumn(name = "team_id")
@ManyToOne(fetch = FetchType.EAGER, cascade = CascadeType.ALL)
private Team team;