休眠/持久性和单例模式 [英] Hibernate/persistence and singleton pattern

问题描述

我有一个单例要保留在数据库中.其他持久化实体应参考此单例.Hibernate如何实现?

I have a singleton that is to be persisted in database. Other persisted entities should have reference to this singleton. How can it be achieved with Hibernate?

我以这样的事情还没有结束，伪造了单身人士的单一ID:

I ended with something not-yet-working like this, faking the single ID of the singleton:

@Entity
@Subselect("select '1' as ID")
class Singleton {
    @Id
    @Column(name="ID")
    private Long getId() { return 1l; }
    private void setId(Long id) { }
}

@Entity
@Table(name="ENT")
class MyEnt {
    // TODO: how to annotate so that table ENT doesn't need foreign key column 
   Singleton s;
}

问题是我不想在引用Singleton的实体中有一列带有外键的列-因为Singleton只是一个，我们不需要它的ID ...

The problem is that I don't want to have a column with foreign key in entities referencing the Singleton - because the singleton is only one and we don't need its ID...

也许我想的是错误的方式?也许是错误的体系结构问题?您解决了类似的问题吗?

Maybe I am thinking in a wrong way? Maybe it is wrong architecture issue? Did you solve similar issue?

推荐答案

我到此为止:

@Entity
@Subselect("select '1' as ID, * from TABLE")
class Singleton {
    @Id
    @Column(name="ID")
    private Long getId() { return 1l; }
    private void setId(Long id) { }
    // ... other useful fields persisted in TABLE
}

@Entity
@Table(name="ENT")
class MyEnt implements Lifecycle {
   Singleton s;
   void onLoad(Session sess, Serializable id) {
      this.s = sess.get(Singleton.class, 1l);
   }
   // etc...
}

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