在 JPA 實體上定義復合主鍵

Question

是否可以在我的實體中定義復合主鍵，但 2 個 ID 是 @OneToOne 字段？ 我正在嘗試使用 @PrimaryKeyJoinColumn 注釋來做到這一點，但沒有成功

public class EmployeeEntity {
// my composite ID must be person_id + department_id
@OneToOne
//@PrimaryKeyJoinColumn(name = "person_id")
private PersonEntity person;
@OneToOne
//@PrimaryKeyJoinColumn(name = "department_id")
private DepartmentEntity department;
// other fields

我絕對可以用兩個數字字段以經典的方式做到這一點，但我想設置一個 OneToOne 關系。

實際上，數據庫模式應該是這樣的：

create table EMPLOYEE
(
PERSON_ID          INT       not null,
DEPARTMENT_ID      INT       not null,
constraint EMPLOYEE_PK
    primary key (PERSON_ID, DEPARTMENT_ID),
constraint EMPLOYEE_PERSON_ID_FK
    foreign key (PERSON_ID) references PERSON (ID),
);

Answer 1

我相信您需要一個可嵌入的復合鍵：

@Entity
public class EmployeeEntity extends BaseEntity {

    @Embeddable
    static class Pk implements Serializable {
        @OneToOne
        @JoinColumn(name = "PERSON_ID")
        private PersonEntity person;

        @OneToOne
        @JoinColumn(name = "DEPARTMENT_ID")
        private DepartmentEntity department;
    }

    @Id
    private final Pk id;

    public EmployeeEntity(DepartmentEntity department, PersonEntity person) {
        this.id = new Pk();
        this.id.person = person;
        this.id.department = department;
    }
}

Answer 2

您應該創建一個包含兩個字段的新 class ，該 class 將成為您的EmployeeEntity的復合鍵。

@Embeddable
public class EmployeeId implements Serializable {
    private PersonEntity person;
    private DepartmentEntity department;

    public EmployeeId() {}

    public EmployeeId(PersonEntity person, DepartmentEntity department) {
        this.person = person;
        this.department = department;
    }

    // equals() and hashCode() methods should also be implemented here
}

public class EmployeeEntity implements Serializable {
    @EmbeddedId
    private EmployeeId id;
}