NHibernate映射一个类的层次结构，其基类是抽象的，鉴别器不是一个字符串 [英] NHibernate mapping with a class hierarchy whose base class is abstract and the discriminator is not a string

问题描述

  public abstract class BaseClass 
 {
 ... 
 
 $ b $ public class ChildClass：BaseClass 
 {
 ... 
} 
  

请注意，父类是抽象的，这是什么给了我一些困难的时候来映射与流利的nhibernate。我的鉴别器是一个字节（DB中的tinyint）。因为它不是一个字符串，我不能设置歧义值的基类，这是行不通的（从BaseClass的映射类）：

<$ （）类型
.SubClass< ChildClass>（）
.IsIdentifiedBy（（byte）OperationType.Plan）
.MapSubClassColumns （p => {...}）

我得到的错误信息是：

类初始化方法UnitTest1.MyClassInitialize抛出异常。 NHibernate.MappingException：NHibernate.MappingException：无法将鉴别值的格式格式化为实体的SQL字符串BaseClass ---> System.FormatException：输入的字符串格式不正确。

<下面的文章似乎解释了会发生什么。他们用xml给出了一个解决方案，但没有流利的nhibernate： http://forum.hibernate.org / b
$ b $ p

<$ p

我已经找到了一个解决方法，但是这看起来像是一个补丁...
我添加了以下内容到映射文件： $ p> SetAttribute（discriminator-value，-1）;


它似乎指示FNH不要使用字符串（我认为它使用类名）抽象基类。
为了使它与-1值一起工作，我也将我的鉴别器类型从字节改为了字节。

编辑：
我错过了：这是DiscriminateSubClassesOnColumn采用默认值的第二个参数。所以我的问题的正确答案是：
$ b $ pre $ DiscriminateSubClassesOnColumn< sbyte>（Type，（sbyte）-1）

Here are the domain model classes:

public abstract class BaseClass
{
...
}

public class ChildClass : BaseClass
{
...
}

Note that the parent class is abstract and this is what gives me some difficulties when comes the time to map with fluent nhibernate. My discriminator is a byte (tinyint in the DB). Because it is not a string and I can't manage to set a discriminator value on the base class, this does not work (taken from the mapping class for BaseClass):

DiscriminateSubClassesOnColumn<byte>("Type")
    .SubClass<ChildClass>()
    .IsIdentifiedBy((byte)OperationType.Plan)
    .MapSubClassColumns(p => { ... })

The error message I get is:

Class Initialization method UnitTest1.MyClassInitialize threw exception. NHibernate.MappingException: NHibernate.MappingException: Could not format discriminator value to SQL string of entity BaseClass ---> System.FormatException: Input string was not in a correct format..

The following post seems to explain what happens. They give a solution with xml but not with fluent nhibernate: http://forum.hibernate.org/viewtopic.php?t=974225

Thanks for the help.

解决方案

I have found a workaround but this seems so like a patch... I added the following to the mapping file:

SetAttribute("discriminator-value", "-1");

It seems to instruct FNH not to use a string (I think it uses the class name) for the abstract base class. To make it work with the -1 value, I also changed my discriminator type from byte to sbyte.

Edit: I missed that: this is the second parameter to DiscriminateSubClassesOnColumn that takes the default value. So the correct answer to my question is:

DiscriminateSubClassesOnColumn<sbyte>("Type", (sbyte)-1)

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