限制Hibernate（和JPA）标准的表现力？ [英] Limitation on the expressiveness of Hibernate (and JPA) Criteria?

问题描述

我在这样的层次结构中有4个实体：

I have 4 entities in a Hierarchy like this:

               Parent
                  |
       ------------------------
       |          |           |
    Child1     Child2       Child3

我有兴趣检索Child1和Child2的所有实例（但不是Child3实例）具有单个查询中的条件。

And I am interested in retrieving All the instances of Child1 and Child2 (but not Child3 instances) with a criteria in a single Query.

这对HQL（或JPQL）来说很容易，如下所示： / p>

This is easy to do with HQL (or JPQL) as follows:

FROM Parent obj  
WHERE obj IN (FROM Child1 where fieldOfChild1="aa") OR   
      obj IN (FROM Child2 where fieldOfChild2=55) 

我研究了Hibernate Criteria和JPA Criteria API，我找不到一种方式来表达此查询作为条件。

I have studied the Hibernate Criteria and JPA Criteria APIs and I cannot find a way to express this query as a Criteria.

这是Criteria API的限制吗？还是只是我错过了路？任何提示？

Is this a limitation of Criteria APIs? or is it just that I missed the way? Any hint?

推荐答案

如果您的映射中的每个子类有一个鉴别器值（例如，对于Child1为1，对于Child2为2 ，3为Child3），您可以使用HQL / Criteria中的特殊属性class。

If you have an discriminator value for each subclass in your mapping (eg. 1 for Child1, 2 for Child2, 3 for Child3) you can use the special attribute "class" in your HQL/Criteria.

因此，标准查询可能如下所示：

So a criteria query could be like this:

session.createCriteria(Parent.class)
       .add(Restrictions.or(Restrictions.eq("class", 1), 
                            Restrictions.eq("class", 2)))

您的HQL查询简化： / p>

And your HQL query simplified:

FROM parent WHERE class = 1 OR class = 2

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