java - Hibernate 提示@OneToOne 中的空@Id，即使它不是空的

Question

我正在尝试实现 @OneToOne 关联，在 Car 和 Person 之间使用相同的 @Id >。 Person 有一个可选的 Car，但是 Car 有一个必需的 Person(因此我需要一个外键在指向现有 Person 的“cars”表中:

@Entity
@Table(name = "persons")
public class Person {

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

    @OneToOne(cascade = CascadeType.ALL, fetch = FetchType.EAGER, mappedBy = "person")
    private Car car;

    /**
     * For hibernate
     */
    @SuppressWarnings("unused")
    private Person() {
    }

    public Person(String name) {
        super();
        this.name = name;
    }

    public Car getCar() {
        return car;
    }

    public void setCar(Car car) {
        this.car = car;
    }

    public String getName() {
        return name;
    }

}

---

@Entity
@Table(name = "cars")
public class Car {
    @Id
    @Column(name = "name")
    private String name;

    @MapsId
    @OneToOne
    @JoinColumn(name = "name")
    @OnDelete(action = OnDeleteAction.CASCADE)
    private Person person;

    public Car() {
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public Person getPerson() {
        return person;
    }

    public void setPerson(Person person) {
        this.person = person;
    }

}

public interface PersonRepository extends CrudRepository<Person, String> {

}

我的测试用例:

@Autowired
private PersonRepository personRepository;

@Test
public void test() {
    Person mike = new Person("Mike");
    personRepository.save(mike); //Saved sucessfully

    Person alice = new Person("Alice");
    Car car = new Car();
    car.setPerson(alice);
    car.setName(alice.getName());
    alice.setCar(car);
    personRepository.save(alice); //error
}

堆栈跟踪:

org.springframework.orm.jpa.JpaSystemException: attempted to assign id from null one-to-one property [com.project.entity.Car.person]; nested exception is org.hibernate.id.IdentifierGenerationException: attempted to assign id from null one-to-one property [com.project.entity.Car.person]

我关注了this solution关于如何拥有共享 ID。数据库中的模式看起来很好，并且完全按照我的意愿工作。如果我删除一辆汽车，什么也不会发生。如果我删除一个拥有 Car 的人，他的 Car 也会从数据库中删除。

问题很简单。 我做错了什么？

万一它起到任何作用(我对此表示怀疑)，这是我的数据源属性:

spring.jpa.hibernate.dll-auto = create-drop
spring.datasource.url=jdbc:mysql://localhost:3306/database?useUnicode=true&characterEncoding=utf-8
spring.datasource.username=root
spring.datasource.password=root
spring.datasource.platform=org.hibernate.dialect.MySQL5InnoDBDialect
spring.jpa.database-platform=org.hibernate.dialect.MySQL5InnoDBDialect

Answer 1

(免责声明:这不是问答)

问题出在 @MapsId 注释中。将其更改为:

@MapsId("name") //Here
@OneToOne
@JoinColumn(name = "name")
@OnDelete(action = OnDeleteAction.CASCADE)
private Person person;

似乎解决了这个问题。