JPA中的雙向關係

我有兩個實體類User和MyCharacter。用戶有一個MyCharacters列表，每個MyCharacter都有一個引用返回給用戶（所有者）。我想要完成的是，我爲這兩個關係使用了同一個連接表，這意味着在MyCharacter中找到的所有者關係會自動使用與User = > MyCharacter相同的連接表。這意味着MyCharacter中的getOwner（）方法應該可以工作，而不必在某處調用setOwner（user）。JPA中的雙向關係

要清除目前無法多做一些事情，這是我的單元測試（最後斷言失敗）


@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()); 
}

我的實體類如下表所示。


@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; 
    } 
}

來源

2009-04-10 Kim L

這就是我們如何加入兩個實體，在我們的項目中JPA：

@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; 
    } 
}

來源

2009-04-10 10:41:05 Vanger