java - JPA中的双向关系

Question

我有两个实体类，User 和 MyCharacter。用户有一个 MyCharacters 列表，每个 MyCharacter 都有一个对用户(所有者)的引用。我想要完成的是，我对这两个关系使用相同的联接表，这意味着，在 MyCharacter 中找到的所有者关系将自动使用与 User=>MyCharacter 中相同的联接表。这意味着 MyCharacter 中的 getOwner() 方法应该可以工作，而无需我在某些时候显式调用 setOwner(user)。

为了更清楚地说明这一点，这是我当前失败的单元测试(最后一个断言失败)

@Test
public void testTwoWayRelation() {
    User user = new User();
    MyCharacter character = new MyCharacter();
    List<MyCharacter> chars = new ArrayList<MyCharacter>();
    chars.add(character);
    user.setCharacters(chars);

    facade.store(user);
    assertNotNull(character.getId());

    character = facade.find(MyCharacter.class, character.getId());

    assertNotNull(character.getOwner());
}

下面列出了我的实体类。

@Entity
@Table(name = "myuser")
public class User {
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    protected Long id;

    @OneToMany(cascade = { CascadeType.PERSIST })
    protected List<MyCharacter> characters;

    public User() {

    }

    public Long getId() {
        return id;
    }

    public void setId(Long id) {
        this.id = id;
    }


    public List<MyCharacter> getCharacters() {
        return characters;
    }

    public void setCharacters(List<MyCharacter> characters) {
        this.characters = characters;
    }

}


@Entity
public class MyCharacter{
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    protected Long id;

    @ManyToOne
    @JoinTable(name = "myuser_mycharacter", joinColumns = @JoinColumn(name = "characters_id"), inverseJoinColumns = { @JoinColumn(name = "user_id") })
    protected User owner;

    public MyCharacter() {

    }

    public Long getId() {
        return id;
    }

    public void setId(Long id) {
        this.id = id;
    }


    public User getOwner() {
        return owner;
    }

    public void setOwner(User owner) {
        this.owner = owner;
    }
}

Answer 1

这就是我们在项目中使用 jpa 连接两个实体的方式:

    @Entity
    @Table(name = "Period")
    public class Period implements Serializable {
      private List<Delay> delays = new ArrayList<Delay>();

      @OneToMany(mappedBy="period") //name of the field in joined entity
      public List<Delay> getDelays() {
        return delays;
      }
    }

   @Entity
   @Table(name = "Delay")
   public class Delay implements Serializable {

    private Period period;

    @ManyToOne
    @JoinColumn(name = "PERIODID")
    public Period getPeriod() {
       return period;
    }   
}