Question

请考虑以下两个表：

表：用户

id (pk)
...

和表UserProfile：

UserProfile
user_id(pk, and fk from User.id. fk is named profile_user_fk)
...

根据这些表，我有实体类：

@Entity
@Table(name="User")
public class User implements Serializable {

    private int id;
    private UserProfile profile;

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

    public void setId(long id) {
        this.id = id;
    }
    @OneToOne(mappedBy = "user")
    public UserProfile getProfie() {
        return profile;
    }

    public void setProfile(UserProfile  p) {
        profile = p;
    }
...
}

And the User class:
@Entity
@Table(name="UserProfile")
public class UserProfile implements Serializable {

    private User user;

    @OneToOne
    @PrimaryKeyJoinColumn(name="profile_user_fk")
    public User getUser() {
        return user;
    }
    public void setUser(User user) {
        this.user = user;
    }
...
}

我不想在UserProfile中添加额外的列，因为我觉得这个列没有意义。 User.id应足以表明UserProfile记录的身份。

所以我认为@OneToOne注释会告诉hibernate用户是pk还是fk，并且应该引用User.id来获取自己的id;但执行代码显示：

org.hibernate.AnnotationException: No identifier specified for entity: xxx.UserProfile

显然我认为错了 - 但我不知道如何在不改变架构的情况下修复它。

请帮忙。谢谢！

Answer 1

错误

No identifier specified for entity: xxx.UserProfile

说

In your Entity class (UserProfile), you have not defined a primary key. You must specify 
either @Id annotation or an @EmbeddedId annotation. Bcoz, every class defined as Entity
with @Entity annotation, needs an @Id or @EmbeddedId property.

修改 UserProfile 类，如下所示： -

@Entity
@Table(name="UserProfile")
public class UserProfile implements Serializable {

    private long uProfileId;
    private User user;

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "uProfileId", nullable = false, unique = true)
    public long getUProfileId() {
        return uProfileId;
    }

    public void setUProfileId(long uProfileId) {
        this.uProfileId = uProfileId;
    }

    @OneToOne
    @PrimaryKeyJoinColumn(name="profile_user_fk")
    public User getUser() {
        return user;
    }
    public void setUser(User user) {
        this.user = user;
    }
    ...
}

阅读： @Entity & @Id and @GeneratedValue Annotations

没有主键的实体类：

如果您不想在 UserProfile 表格中添加主键，则可以使用 @Embedded＆amp; xml映射中的@Embeddable注释或 <component> 标记。有关此内容的更多解释，请参阅以下帖子： -

Hibernate在作为主键的另一个实体上进行一对一映射

1 个答案: