NHibernate多对一级联 [英] NHibernate Many-to-one cascade

问题描述

我有以下两个课程:

public class Project
{

    public virtual int ProjectId { get; set; }
    public virtual string ProjectName { get; set; }
    public virtual LegalEntity LegalEntity { get; set; }
}

和

public class LegalEntity
{
    public virtual int LegalEntId { get; set; }
    public virtual string Name { get; set; }
}

映射为:

<class name="Project" table="Project" dynamic-update="true">
  <id name="ProjectId">
    <generator class="native"/>
  </id>  

  <property name="ProjectName" />
  <many-to-one name="LegalEntity" column="LegalEntId" fetch="join" cascade="all-delete-orphan" />


</class>

和

<class name="LegalEntity" table="LegalEnt" dynamic-update="true">

  <id name="LegalEntId">

    <generator class="native"/>

  </id>



  <property name="Name" />    

</class>

在数据库中，项目"表的FK指向LegalEntity的PK列.一个项目只有一个法人实体.不同的项目可以具有相同的法人实体.这就是我多对一的原因.不确定这是否正确.

In database, Project table has a FK to LegalEntity's PK column. One Project will have only one legal entity. Different projects can have same legal entity. So thats the reason I have gone for many-to-one. Not sure if this is correct though.

插入和更新工作正常.但是，如果我更新了项目中的法人实体ID，并且该法人实体成为孤立的，我希望将其删除.但是它没有发生.在理解所有删除孤岛上我错了吗?如果是，我如何实现此行为?

Insert and update is working fine. But if I update a legal entity id in a project and that legal entity becomes orphan, I want it to be deleted. But its not happening. Am I wrong in understanding delete-all-orphan? If yes, how can I achieve this behaviour?

推荐答案

many-to-one级联不支持all-delete-orphan，请参见:

The many-to-one cascade does not support all-delete-orphan, see:

• 5.1.10.多对一

<many-to-one
    ...
    cascade="all|none|save-update|delete"              (4)
    ...

此外，在NHibernate的会话中几乎不可能处理此功能.因为不必清楚，所以引用的many-to-one确实是孤立的.数据库中应该做一些更进一步的检查...可能还有其他地方引用此表行...

Also, it would be almost impossible to handle this feature by NHibernate's session. Because it does not have to be clear, that the referenced many-to-one is really orphan. There should be some farther checks in DB... there could be other places referencing this table row...

建议:作为DAO或Business Facade实施的一部分，在您的代码中进行.检查是否确实存在没有依赖项，然后发出明确的Delete()

Suggestion: do it in your code as a part of the DAO or Business Facade implementation. Check if there are really no dependencies, and then issue explicit Delete()

EXTEND:这是一种QueryOver语法，用于获取所有"orphan" LegalEntity

EXTEND: Here is a QueryOver syntax to get a list of all "orphan" LegalEntity

// subquery
var subquery = QueryOver.Of<Project>()
    .Select(x => x.LegalEntity.LegalEntId);

// just these legal entities, which are NOT used
var query = session.QueryOver<LegalEntity>()
    .WithSubquery
      .WhereProperty(y => y.LegalEntId)
      .NotIn(subquery)
    ;

// orphans
var list = query
    .List<LegalEntity>();

这篇关于NHibernate多对一级联的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！