Java 一对一关系中的外键休眠

我在以下两个实体之间有一对一的关系：

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

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

    @Column
    private String name;

    @Column
    private String email;

    @Column
    private String password;

    @OneToOne(cascade = CascadeType.PERSIST, fetch = FetchType.EAGER)
    @JoinColumn(name = "user_role_id", referencedColumnName = "id")
    private UserRole userRole;

我还使用EntityManagerFactory在本地数据库中创建表。我收到了这个代码，我必须遵守它

public class UserRepo {

    private EntityManagerFactory entityManagerFactory = Persistence.createEntityManagerFactory("ro.tutorial.lab.SD");

    public void insertNewUser(User user) {
        EntityManager em = entityManagerFactory.createEntityManager();
        em.getTransaction().begin();
        em.persist(user);
        em.getTransaction().commit();
        em.close();
    }

还有一个类似的UserRoleRepo

我的问题是，在main中实例化时，我不知道如何仅获取FK-in用户的UserRole id。相反，我得到了整个userRole实例和错误“重复条目‘b36fcb4c-3904-4205-888b-9792f24d8b5c’作为键‘userRole.PRIMARY’”

---

看起来我很困惑，正确的关系是UserRole和User表之间的一对多关系。现在它工作得很好

public class UserRepo {

    private EntityManagerFactory entityManagerFactory = Persistence.createEntityManagerFactory("ro.tutorial.lab.SD");

    public void insertNewUser(User user) {
        EntityManager em = entityManagerFactory.createEntityManager();
        em.getTransaction().begin();
        em.persist(user);
        em.getTransaction().commit();
        em.close();
    }

public static void main(String[] args) {
        UserRoleRepo userRoleRepo= new UserRoleRepo();

        UserRole userRole1 = new UserRole();
        userRole1.setId(UUID.randomUUID().toString());
        System.out.println(userRole1);
        userRole1.setDescription("admin");
        userRoleRepo.insertNewUser(userRole1);

        UserRole userRole2 = new UserRole();
        userRole2.setId(UUID.randomUUID().toString());
        System.out.println(userRole2);
        userRole2.setDescription("client");
        userRoleRepo.insertNewUser(userRole2);

        UserRepo userRepo= new UserRepo();

        User user = new User();
        user.setId(UUID.randomUUID().toString());
        user.setName("Todoran");
        user.setEmail("todoran@utcluj.ro");
        user.setPassword("mona");
        user.setUserRole(userRole1); //////////it breaks here :(((((
        System.out.println(user);
        userRepo.insertNewUser(user);

    }