Hibernate - 持久化多态连接 [英] Hibernate - Persisting polymorphic joins

问题描述

例如：
$ b



$ b我想了解如何最好地实现hibernate中的多态一对多。 $ b

  @MappedSuperclass 
公共类BaseEntity {
整数id; 
 //等等... 
} 
 
 @Entity 
 public class作者extends BaseEntity {} 
 
 @Entity 
公共类Post扩展BaseEntity {} 
 
 @Entity 
 public class Comment BaseEntity {} 
  

现在，我还想坚持审计信息，与以下类：

  @实体
 public class AuditEvent {
 @ManyToOne //？ 
 BaseEntity实体; 
 
 $ / code> 

auditEvent.entity ？另外，Hibernate会如何坚持下去？会生成一系列连接表（ AuditEvent_Author ， AuditEvent_Post ， AuditEvent_Comment
注意，我宁愿没有其他实体类暴露连接的另一端（例如， 在 BaseEntity ）上列出< AuditEvent>事件 - 但如果这是最简洁的实现方式，那就足够了。 / p>


解决方案

映射超类不是实体，因此不能成为关联的一部分（如 EJB-199 ）。所以：



• 使您的 BaseEntity 摘要并使用 TABLE_PER_CLASS 策略（请参阅此上一个答案）


• 在层次结构中引入另一个 AuditableEntity 实体，并使用最为您的用例提供适当的继承策略。


考虑使用 Envers

I'm trying to understand how to best implement a polymorphic one-to-many in hibernate.

Eg:

@MappedSuperclass
public class BaseEntity  {
    Integer id;
    // etc...
}

@Entity
public class Author extends BaseEntity {}

@Entity
public class Post extends BaseEntity {}

@Entity
public class Comment extends BaseEntity {}

And now, I'd like to also persist audit information, with the following class:

@Entity
public class AuditEvent {
    @ManyToOne // ?
    BaseEntity entity;
}

What is the appropriate mapping for auditEvent.entity? Also, how will Hibernate actually persist this? Would a series of join tables be generated (AuditEvent_Author , AuditEvent_Post, AuditEvent_Comment), or is there a better way?

Note, I'd rather not have my other entity classes expose the other side of the join (eg., List<AuditEvent> events on BaseEntity) - but if that's the cleanest way to implement, then it will suffice.

解决方案

A mapped superclass is not an entity and thus can't be part of an association (as reminded in EJB-199). So either:

• make your BaseEntity abstract and use a TABLE_PER_CLASS strategy (see this previous answer)
• introduce another AuditableEntity entity in the hierarchy and use what would be the most appropriate inheritance strategy for your use case.
• consider using Envers

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