在子类的Hibernate上为每个表指定不同的序列 [英] Specifying distinct sequence per table in Hibernate on subclasses

问题描述

我们的应用程序中的所有实体都扩展了一个超类。

在Hibernate中，是否有一种方法可以为每个表指定不同的序列？ DataObject 像这样：

  @MappedSuperclass 
 public abstract class DataObject实现Serializable {
 @Id 
 @GeneratedValue（strategy = GenerationType.SEQUENCE）
 @Column（name =id）
 private int id; 
 
 
 $ Entity 
 @Table（name =entity_a）
 public class EntityA extends DataObject {...} 
 
 @Entity 
 @Table（name =entity_b）
 public class EntityB extends DataObject {...} 
  

这会导致所有实体使用共享序列，默认 hibernate_sequence 。

我想要做的是为每个实体使用一个单独的序列，例如上例中的 entity_a_sequence 和 entity_b_sequence 。如果在子类上指定了ID，那么我可以使用 @SequenceGenerator 注释为每个实体指定一个序列，但在这种情况下，ID在超类上。鉴于ID是超类，是否有一种方法可以为每个实体使用一个单独的序列 - 如果是，如何？

（我们使用的是PostgreSQL 8.3，以防相关） 解决方案

你试过这样做吗？

  @MappedSuperclass 
 public abstract class DataObject实现了Serializable {
 @Id 
 @GeneratedValue（strategy = GenerationType.SEQUENCE，generator =idgen）
 @Column（name =id）
 private int id; 
 
 $ b @Entity 
 @SequenceGenerator（initialValue = 1，name =idgen，sequenceName =entityaseq）
 @Table（name =entity_a ）
 public class EntityA extends DataObject {
 
} 
 
 @Entity 
 @SequenceGenerator（initialValue = 1，name =idgen，sequenceName = entitybseq）
 @Table（name =entity_b）
 public class EntityB extends DataObject {
 
} 
  

对不起，我现在没有必要的环境来测试它，但我会稍后再试。

Is there a way to specify distinct sequences for each table in Hibernate, if the ID is defined on a mapped superclass?

All entities in our application extend a superclass called DataObject like this:

@MappedSuperclass
public abstract class DataObject implements Serializable {
    @Id 
    @GeneratedValue(strategy = GenerationType.SEQUENCE)
    @Column(name = "id")
    private int id;
}

@Entity
@Table(name = "entity_a")
public class EntityA extends DataObject { ... }

@Entity
@Table(name = "entity_b")
public class EntityB extends DataObject { ... }

This causes all entities to use a shared sequence, the default hibernate_sequence.

What I would like to do is use a separate sequence for each entity, for example entity_a_sequence and entity_b_sequence in the example above. If the ID were specified on the subclasses then I could use the @SequenceGenerator annotation to specify a sequence for each entity, but in this case the ID is on the superclass. Given that ID is in the superclass, is there a way I can use a separate sequence for each entity — and if so, how?

(We are using PostgreSQL 8.3, in case that's relevant)

解决方案

Have you tried doing it this way ?

@MappedSuperclass
public abstract class DataObject implements Serializable {
    @Id 
    @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "idgen")
    @Column(name = "id")
    private int id;
}

@Entity
@SequenceGenerator(initialValue = 1, name = "idgen", sequenceName = "entityaseq")
@Table(name = "entity_a")
public class EntityA extends DataObject { 

}

@Entity
@SequenceGenerator(initialValue = 1, name = "idgen", sequenceName = "entitybseq")
@Table(name = "entity_b")
public class EntityB extends DataObject {

}

I'm sorry I don't have the required environment to test it right now but I'll try it later.

这篇关于在子类的Hibernate上为每个表指定不同的序列的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！