java - Eclipse 链接/JPA : Multiple @DiscriminatorColumn annotations for Entity

Question

我正在 EclipseLink 中寻找一种在同一实体上有两个 @DiscriminatorColumns 的方法

我的 PostreSQL 数据库表是:

Dictionary
{
  id,
  object_type,
  attribute_type,
  translation
}

类是:

@Entity
@Table(name = "dictionary")
@Inheritance(strategy=InheritanceType.SINGLE_TABLE)
@DiscriminatorColumn(name="object_type", 
                     discriminatorType=DiscriminatorType.INTEGER)
public class DictionaryRow implements Serializable;

@Entity
@DiscriminatorValue("0")
@DiscriminatorColumn(name="info_type", 
                     discriminatorType=DiscriminatorType.INTEGER)
@Inheritance(strategy=InheritanceType.SINGLE_TABLE)
public class DictionaryAttribute extends DictionaryRow;

@Entity
@DiscriminatorValue("1")
public class DictionaryAttributeName extends DictionaryAttribute;

我想要实现的是，当我调用 DictionaryAttributeName 时，它​​将被解析为 SQL，如下所示:

select * from DICTIONARY where info_type = 1 and object_type = 0

但实际上，它从 DictionaryRow 类中获取 DiscriminatorColumn，从 DictionaryAttributeName 中获取 DiscriminatorValue，导致完全错误的 SQL:

select * from DICTIONARY where object_type = 1

这个问题有解决方案吗？

谢谢

Answer 1

根据 JPA 2.0 规范，这是不可能的:

11.1.10 DiscriminatorColumn Annotation

For the SINGLE_TABLE mapping strategy, and typically also for the JOINED strategy, the persistence provider will use a type discriminator column. The DiscriminatorColumn annotation is used to define the discriminator column for the SINGLE_TABLE and JOINED inheritance mapping strategies.

The strategy and the discriminator column are only specified in the root of an entity class hierarchy or subhierarchy in which a different inheritance strategy is applied.

引用资料

• JPA 2.0 规范
  • 第 11.1.10 节“鉴别器列注释”