NHibernate 通过外键将子类属性映射到另一个对象

发布于 2024-11-05 20:34:49 字数 1337 浏览 0 评论 0原文

我正在研究一个不完美的现有数据结构，并且我有一个继承映射问题需要解决。

我在每个层次结构中使用一个表，并设置了带有鉴别器的子类。然而，子类属性是返回其他表的外键。如何设置子类映射，以便在查询 fk 属性时得到一个对象而不是 null？这可能吗？

我当前的映射

<?xml version="1.0" encoding="utf-8" ?>
      <hibernate-mapping xmlns="urn:nhibernate-mapping-2.2" assembly="MVC3" namespace="MVC3.Models">
  <class name="Image" table="Images">
<id name="Id" column="ImageId">
  <generator class="identity" />
</id>
<discriminator column="ImageType" />
<property name="Url" column="Url" not-null="true" />
<property name="Caption" column="Caption" />
<subclass name="AupairImage" discriminator-value="AupairImage">
  <join table="Aupairs" inverse="true">
    <key column="AupairId" />
    <many-to-one name="Aupair" column="AupairId" class="Aupair" />
  </join>
</subclass>
<subclass name="FamilyImage" discriminator-value="FamilyImage">
  <join table="Families" inverse="true">
    <key column="FamilyId" />
    <many-to-one name="Family" column="FamilyId" class="Family" />
  </join>      
</subclass>

我想添加一个实体图，但我还不能发布图像:0(

但是外键 AupairId 和 FamilyId 链接回另外两个表，并且类型为 int 32

我知道最好重组 Aupair 并且家庭实体有一个层次结构来摆脱图像中的层次结构，但由于现有代码，这将是最后的手段，

在此先感谢您的地图专家提供的任何帮助......

原文

I am working on an existing data structure that is not perfect and I have an inheritance mapping issue to solve.

I am using a table per hierarchy and have subclasses with discriminators set up. However the subclassed properties are foreign keys back to other tables. How do I set up my subclass mapping so that when I query the fk property I get an object rather than null? Is this even possible?

My current Mapping

<?xml version="1.0" encoding="utf-8" ?>
      <hibernate-mapping xmlns="urn:nhibernate-mapping-2.2" assembly="MVC3" namespace="MVC3.Models">
  <class name="Image" table="Images">
<id name="Id" column="ImageId">
  <generator class="identity" />
</id>
<discriminator column="ImageType" />
<property name="Url" column="Url" not-null="true" />
<property name="Caption" column="Caption" />
<subclass name="AupairImage" discriminator-value="AupairImage">
  <join table="Aupairs" inverse="true">
    <key column="AupairId" />
    <many-to-one name="Aupair" column="AupairId" class="Aupair" />
  </join>
</subclass>
<subclass name="FamilyImage" discriminator-value="FamilyImage">
  <join table="Families" inverse="true">
    <key column="FamilyId" />
    <many-to-one name="Family" column="FamilyId" class="Family" />
  </join>      
</subclass>

I would have like to add an entity diagram but I cannot post images yet :0(

But the foreign keys AupairId and FamilyId link off back to two other tables and are of the type int 32

I know it would be better to restructure the Aupair And Family entities to have a hierarchy to get rid of the one in images but this would be a last resort due to existing code.

Thanks in advance any help appreciated from you mapping experts....

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或十年 2024-11-12 20:34:49

再看一眼后意识到我做错了什么，应该在子类下使用具有定义列的多对一

    <subclass name="MVC3.Models.FamilyImage, MVC3" discriminator-value="FamilyImage">
     <many-to-one cascade="all" class="MVC3.Models.Family, MVC3" name="Family">
        <column name="FamilyId" />
      </many-to-one>
    </subclass>

Realised what I was doing wrong after taking a second look, should have just used a Many-To-One under the Subclass with a defined column

    <subclass name="MVC3.Models.FamilyImage, MVC3" discriminator-value="FamilyImage">
     <many-to-one cascade="all" class="MVC3.Models.Family, MVC3" name="Family">
        <column name="FamilyId" />
      </many-to-one>
    </subclass>

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