Hibernate @JoinFormula

问题描述

我有两个实体A和B.

  public class A {
 
 @Id 
 @GeneratedValue 
私人整数ID; 
 
私人字符串uuid; 
 
 ... 
} 
  

UUID由外部给出; ID可以看作是版本。

现在，我想引用B中的A，这样我就可以将存储在B中的uuid自动选择

  public class B {
 @Id 
 @GeneratedValue 
 private Integer id; 
 
私人字符串uuidOfA; 
 
 @ManyToOne 
 @JoinFormula（value =SELECT a.id FROM A WHERE v.uuid = uuidOfA AND v.id =（SELECT max（x.id）FROM x WHERE x.uuid = v.uuid），referencedColumnName =id）
 private A a; 
 
 ... 
} 
  

这将创建一列在B中包含A的id，如果我尝试持久化一个对象，则会引发异常。我也试过@JoinColumnsOrFormulas，但没有幸运。

有人可以告诉我如何做到这一点（在Hibernate 3.5 btw中）？

谢谢！

解决方案

  @ManyToOne 
 @JoinColumnsOrFormulas（{
 @JoinColumnOrFormula（formula = @ JoinFormula（value =（SELECT a.id FROM A a WHERE a.uuid = $ uid），referencedColumnName =id）），
 @JoinColumnOrFormula（column = @JoinColumn（uuidOfA，referencedColumnName =uuid））
}）
 private A a; 
  

I have two entities A and B.

 public class A{

    @Id
    @GeneratedValue
    private Integer id;

    private String uuid;

    ...
  }

The UUID is given externally; ID can be seen as version.

Now, I'd like to reference A in B such that I have the uuid stored in B and automatically select the A with the according uuid and the highest id.

What I tried is:

public class B{
      @Id 
      @GeneratedValue
      private Integer id;

      private String uuidOfA;

      @ManyToOne
      @JoinFormula(value="SELECT a.id FROM A a WHERE v.uuid = uuidOfA AND v.id = (SELECT max(x.id) FROM A x WHERE x.uuid = v.uuid)", referencedColumnName="id")
      private A a; 

      ...        
}

This will create a column containing A's id in B and throws an exception if I try to persist an object. I've also tried @JoinColumnsOrFormulas without luck.

Can someone give me a hint on how to do this (in Hibernate 3.5 btw)?

Thanks!

解决方案

The following works:

@ManyToOne
@JoinColumnsOrFormulas({
  @JoinColumnOrFormula(formula=@JoinFormula(value="(SELECT a.id FROM A a WHERE a.uuid = uuid)", referencedColumnName="id")),
  @JoinColumnOrFormula(column = @JoinColumn("uuidOfA", referencedColumnName="uuid"))
})
private A a;

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