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jpa-hibernate复合外键映射

jpa hibernate java

broschb · 技术社区 · 14 年前

我在为某些实体设置jpa映射时遇到问题。我有一个定义如下的父实体。

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

    private static final long serialVersionUID = 1L;

    @Id
    @GeneratedValue(generator="eif_inst_gen")
    @SequenceGenerator(name="eif_inst_gen",sequenceName="EIF_INSTANCE_SEQ")
    @Column(name = "EAIH_ID")
    private Long eaihid;

    @Column(name = "EAD_ID")
    private Long eadid;

    @OneToMany(targetEntity=InstanceNotifyEntity.class, mappedBy="instance",fetch=FetchType.EAGER, cascade = CascadeType.ALL)
    private List<InstanceNotifyEntity> userDetails = new ArrayList<InstanceNotifyEntity>();

}

然后,我有一个子实体和一个复合键,还有一个外键指向这个表的主键,如下所示:

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

    private static final long serialVersionUID = 1L;
    
    @Id
    @ManyToOne
    @JoinColumn(name="EAIH_ID", referencedColumnName="EAIH_ID")
    private InstanceEntity instance;
    
    @Id
    @Column(name="USER_ID")
    private Long userId;

    @Column(name="COMMENT_TXT")
    private String commentText;

}

我知道子实体是不正确的,但我不确定如何设置这个有一个复合PK。我知道我需要设置一个PK类,但是当一个字段是父类的外键时,我不知道如何设置。一旦设置完成,父实体将如何引用子实体?

感谢您的帮助。

2 回复 | 直到 4 年前

ScottM 8 年前

这取决于 JPA 2 spec

如规范中所述,在这种情况下,有两种方法可以表示子实体的键:

@IdClass
@EmbeddedId

EmbeddedId 是的。我选择了 嵌入ID 武断的,但是 IdClass 和 嵌入ID 意义重大。你可能会做出不同的选择。

// Child entity's composite primary key
@Embeddable
public class InstanceNotifyEntityId implements Serializable {
    Long eaihId;
    Long userId;
}

// Child entity
@Entity
@Table(name="EIF_INST_NOTIFIED")
public class InstanceNotifyEntity implements Serializable {
    @AttributeOverrides({
      @AttributeOverride(name="userId", column = @Column(name="USER_ID"))
      @AttributeOverride(name="eaihId", column = @Column(name="EAIH_ID"))
    })
    @EmbeddedId
    InstanceNotifyEntityId id;

    @MapsId("eaihId")
    @ManyToOne
    InstanceEntity instance;

    // ...
 }

userDetails mappedBy

buræquete Naveen Kocherla 6 年前

我也面临同样的问题,并遵循这个答案,但它不是保存子实体与父实体。这是我所做的改动,效果很好。进行以下更改-

// Child entity's composite primary key class

public class InstanceNotifyEntityId implements Serializable {

    @Column(name = "USER_ID")
    Long userId;

    @JoinColumn(name = "EAIH_ID")
    @ManyToOne  
    InstanceEntity instance
}

// Child entity which contain composite primary key as a EmbeddedId, 
// no need to define any relationship here as we already define 
// the relationship in composite key class. 

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

    @EmbeddedId
    InstanceNotifyEntityId id;
}


// Parent entity (parent entity mappedby should be your composite 
// key class instance.child class object which already have the 
// join column mapping with "EAID_ID")  

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

    @OneToMany(mappedBy = "id.instance,fetch=FetchType.EAGER, cascade = CascadeType.ALL)
    private List<InstanceNotifyEntity> userDetails = new ArrayList<InstanceNotifyEntity>();
}

在保存父实体时,将父对象设置为复合键,如 id.setInstance(parent entire obj)