Question

我是JPA /休眠的新手，我正在创建一个简单的联接以在不同的表中获取一些数据让我们这样看：

目的是基于M_USER.username列获取M_PROFILE数据，但是很明显，您看到M_PROFILE表中没有外键。

我只是尝试使用下面的代码，但没有结果，总是出现错误。

用户实体类

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

        @Id
        @Column(name = "id")
        private String uuid;

        @Column(name = "email")
        private String email;

        @Column(name = "username")
        private String username;

        @OneToOne(fetch = FetchType.LAZY)
        @MapsId("username")
        private Profile profile;

        public String getId() {
            return id;
        }
        public void setId(String id) {
            this.id = id;
        }

        public String getEmail() {
            return email;
        }
        public void setEmail(String email) {
            this.email = email;
        }

        public String getUsername() {
            return username;
        }
        public void setUsername(String username) {
            this.username = username;
        }

        public Profile getProfile() {
            return profile;
        }
        public void setProfile(Profile profile) {
            this.profile = profile;
        }
    }

配置文件实体类

@Entity
@Table(name = "M_PROFILE")
public class Profile {

    private String username;
    private String phone;
    private String address;

    @Id
    @Column(name = "username", nullable = false)
    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    @Basic
    @Column(name = "phone")
    public String getPhone() {
        return phone;
    }

    public void setPhone(String phone) {
        this.phone = phone;
    }

    @Basic
    @Column(name = "address")
    public String getAddress() {
        return address;
    }

    public void setAddress(String address) {
        this.address = address;
    }
}

致电

时出现不同的错误

User user = userRepository.findByUsername("aswzen");
String phone = user.getProfile().getPhone();

例如这个。

“ USER0 _”。“ PROFILE_USERNAME”：无效的标识符

需要帮助，在此先感谢

注意：我没有更改表的权限。

Answer 1

尝试指定联接列：

@OneToOne
@JoinColumn(name = "username", referencedColumnName = "username")
private profile profile;

您在这里并不需要@MapsId。

Answer 2

我建议创建具有表关系的第三张表

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

@OneToOne(fetch = FetchType.LAZY)
@JoinTable(
name = "user_profile",
joinColumns = @JoinColumn(name="user_id"),
inverseJoinColumns = @JoinColumn(name="profile_username")
 )
private Profile profile;


UPDATE user_profile 
SET user_id = (
    SELECT id
    FROM M_USER
);


UPDATE user_profile 
SET profile_username = (
    SELECT username
    FROM M_USER
);

没有外键的JPA OneToOne关联始终会失败

2 个答案: