如何使用关系OneToOne将两个相关对象保存到数据库 [英] How to save two related objects to data base with relation OneToOne

问题描述

当我尝试保存U对象时，出现下一个异常:

When I'm trying to save an U object I got next exception:

org.springframework.orm.jpa.JpaSystemException:尝试从空的一对一属性[com.roc.domain.A.user]分配ID；嵌套的异常是org.hibernate.id.IdentifierGenerationException:尝试从空的一对一属性[com.roc.domain.A.user]中分配ID.

org.springframework.orm.jpa.JpaSystemException: attempted to assign id from null one-to-one property [com.roc.domain.A.user]; nested exception is org.hibernate.id.IdentifierGenerationException: attempted to assign id from null one-to-one property [com.roc.domain.A.user]

我有两个表: 1.用户，其列为id(自动incr，primary)，名称. 2.与该列联系的是id，user_id(即外键-> user.id)和地址.

I have two tables: 1. user that columns are id(auto incr, primary), name. 2. contact that columns are id, user_id(that is foreign key -> user.id) and address.

@Entity
@Table(name = "a")
public class A {
  @Id
  @GeneratedValue(strategy = GenerationType.IDENTITY)
  @Column(name = "id")
  private Long id;

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

  @OneToOne
  @MapsId
  private U user;

  public A() {

  }
   // getters and setters



}


@Entity
@Table(name = "u")
public class U {
  @Id
  @GeneratedValue(strategy = GenerationType.IDENTITY)
  @Column(name = "id")
  private Long id;
  @Column(name="username")
  private String userName;
  @JoinColumn(name = "user_id", referencedColumnName = "id")
  @OneToOne(mappedBy = "user", cascade = CascadeType.ALL)
  private A a;

  public U(){};

}

@RunWith(SpringRunner.class)
@SpringBootTest
public class ApplicationTest {

  @Autowired
  private URepository uRepository;

  @Test
  public void simpleCrudTest() {
    U user = new U("name", new A("address"));
    uRepository.save(user);


  }
}

推荐答案

您已经正确设置了层叠，但是由于这种关系是双向的，因此您需要在内存模型中设置双方.

You have set the cascade correctly however because the relationship is bi-directional you need to set both sides in the in-memory model.

  @Test
  public void simpleCrudTest() {
    U user = new U("name", new A("address"));

   //will work when this is added 
   a.setUser(user);
   uRepository.save(user);

  }

否则，由于错误状态，A在保存时为用户提供了空引用.

Otherwise, as the error states, A has a null reference for user on save.

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