java - 外键中的 JPA/Hibernate OneToOne Null

Question

我有以下两个具有双向 OneToOne 关系映射的实体，数据访问由 Hibernate EntityManager v.“3.5.1-Final”提供。

@Entity
@Table(name = "details")
public class Details {
    private Long id;
    private User user;

    public void setUser(User user) {
        this.user = user;
    }

    @OneToOne  
    @JoinColumn(name="user_id") 
    public User getUser() {
        return user;
    }

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "id", unique = true, nullable = false)
    public Long getId() {
        return id;
    }

    private void setId(Long id) {
        this.id = id;
    }
}

和:

@Entity
@Table(name = "users")
public class User {
private Long id;
private Details details;

public void setDetails(Details details) {
    this.details = details;
}

@OneToOne(mappedBy="user",cascade=CascadeType.ALL)  
public Details getDetails() {
    return details;
}
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "id", unique = true, nullable = false)
    public Long getId() {
        return id;
    }

    private void setId(Long id) {
        this.id = id;
    }
}

持久化代码:

User user = new User();
Details details = new Details();
user.setDetails(details);

entityManager.persist(user);

然后数据被正确地插入到两个表中，问题是详细表“user_id”中的 FK 变为空，不确定这里缺少什么。

Answer 1

你需要添加details.setUser(user).

user.setDetails(details); 仅在 User 实体中设置外键。 @OneToOne 只告诉 hibernate 如何解释返回的数据(以及如何获取 - 使用连接)。它不会告诉 Hibernate 要设置哪些外键。