覆盖@CollectionTable对主键列的引用 [英] Override @CollectionTable reference to primary-key column

问题描述

JPA文档指出 CollectionTable.joinColumns 属性是收集表的外键列，它们引用实体的主表."

JPA documentation says that CollectionTable.joinColumns property is "The foreign key columns of the collection table which reference the primary table of the entity."

我可以使其不引用实体表的主键列，而是引用具有唯一值的另一列吗?

Can I make it reference not the primary key column of the entity table, but another column which has unique values?

有一个具有以下表的遗留数据库(简化):

There is a legacy database with following tables (simplified):

staff:
  user_id (int)
  user_name (varchar, primary key)

staff_privileges:
  id_user (int)
  privileges_id (int) 
  privileges_status (boolean)

现在，我将Hibernate引入项目，并尝试将此表映射到实体:

Now I'm introducing Hibernate into the project and trying to map this tables to the entity:

@Entity
@Table(name = "staff")
public class User {

  @Column(name = "user_id")
  private Integer userId;

  @Id
  @Column(name = "user_name")
  private String userName;    // primary key column (legacy, cannot be changed)

  @ElementCollection
  @CollectionTable(name = "staff_privileges", joinColumns = @JoinColumn(name = "id_user"))
  @MapKeyColumn(name = "privileges_id")
  @Column(name = "privileges_status")
  private Map<Integer, Boolean> privileges; // privilegeId <-> isEnabled
}

不起作用，因为@CollectionTable创建对主键staff_privileges.id_user -> staff.user_name (primary key)的引用. 它应该是:staff_privileges.id_user -> staff.id_user. 有没有办法覆盖此参考?是否有任何Hibernate或JPA注释?我想保持简单，如果可能的话，不要引入任何新的Entity或Embeddable.

Won't work because @CollectionTable creates reference to primary key: staff_privileges.id_user -> staff.user_name (primary key). It should be: staff_privileges.id_user -> staff.id_user. Is there way to override this reference? Are there any Hibernate or JPA annotations for this? I would like to keep things simple and not introduce any new Entity or Embeddable if possible.

推荐答案

假设每个用户的user_id也是唯一的，那么您只需将User上的@Id批注移动到userId:您的JPA提供者不知道数据库中实际的PK是什么，只要该值是唯一的，就不会引起任何问题.

Assuming that user_id in also unique for each User then you could simply move the @Id annotation on User to userId: your JPA provider has no knowledge of what the actual PK is in the database so as long as that value is unique it would not cause any issues.

上下文略有不同，但请参见:

Slightly different context but see:

https://en.wikibooks.org/wiki/Java_Persistence/Identity_and_Sequencing#No_Primary_Key

JPA ID不一定总是与数据库表主数据库匹配 键约束，也不需要主键或唯一约束.

The JPA Id does not always have to match the database table primary key constraint, nor is a primary key or a unique constraint required.

唯一的区别是，如果您从映射中对表进行反向工程，则将使用user_id而非user_name上的PK创建人员表.

The only difference would be if you were reverse engineering your tables from your mappings then the staff table would be created with PK on user_id rather than user_name.

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