Question

我必须使用hibernate并且不太确定如何解决这个问题，我有2个表与1..n这样的关系：

-------
TABLE_A
-------
first_id (pk)
second_id (pk)
[other fields]

-------
TABLE_B
-------
first_id (pk)(fk TABLE_A.first_id)
second_id (pk)(fk TABLE_A.second_id)
third_id (pk)
[other fields]

如何使用Hibernate ???

来管理它

我不知道如何管理第二个表的主键...

Answer 1

有一个例子与Hibernate reference documentation中的案例完全相似。就在这个例子之前，你会找到解释。以下是与您的问题相匹配的示例（用户是表A，而客户是表B）：

@Entity
class Customer {
   @EmbeddedId CustomerId id;
   boolean preferredCustomer;

   @MapsId("userId")
   @JoinColumns({
      @JoinColumn(name="userfirstname_fk", referencedColumnName="firstName"),
      @JoinColumn(name="userlastname_fk", referencedColumnName="lastName")
   })
   @OneToOne User user;
}

@Embeddable
class CustomerId implements Serializable {
   UserId userId;
   String customerNumber;

   //implements equals and hashCode
}

@Entity 
class User {
   @EmbeddedId UserId id;
   Integer age;
}

@Embeddable
class UserId implements Serializable {
   String firstName;
   String lastName;

   //implements equals and hashCode
}

注意：对于这两个表，有一个代理标识符要简单得多。除非你被迫处理遗留架构，否则请帮忙并使用代理键。

Answer 2

使用@PrimaryKeyJoinColumn和@PrimaryKeyJoinColumns注释。来自Hibernate manual：

@PrimaryKeyJoinColumn注释确实表示实体的主键用作关联实体的外键值。

Answer 3

public class User implements Serializable {
    /**
     * 
     */
    private static final long serialVersionUID = 5478661842746845130L;
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private int id;
}
@Entity
public class Author {

    @Id
    @Column(name = "AUTHOR_ID", nullable = false)
    private int authorId;
    @Column(name = "ENABLED", nullable = false, length = 1)
    private boolean enabled;

    @OneToOne
    @MapsId
    @JoinColumn(name = "AUTHOR_ID", referencedColumnName = "ID", nullable = false, insertable = false, updatable = false)
    User user;

    public boolean isEnabled() {
        return enabled;
    }

    public void setEnabled(boolean enabled) {
        this.enabled = enabled;
    }

    public User getUser() {
        return user;
    }

    public void setUser(User user) {
        this.user = user;
    }

}

Hibernate外键作为主键的一部分

3 个答案: