FluentNHibernate - 将一个类映射到多个表 [英] FluentNHibernate - Mapping a class to multiple tables

问题描述

抱歉问了一个冗长的问题.但值得提供所有细节，所以请耐心等待.

Sorry for a lengthy question. But it is worth giving all the details so please bear with me through to the end.

我正在处理一个我没有太多控制权的旧数据库.我希望能够将一个类映射到多个数据库表.这是我的表格的外观

I'm working against a legacy database over which I do not have much control. I want to be able to map a class to multiple database tables. Here is how my tables look

查找

+--------+--------------+------------+
| Column |   DataType   | Attributes |
+--------+--------------+------------+
| Id     | INT          | PK         |
| Code   | NVARCHAR(50) |            |
+--------+--------------+------------+

文化

+--------------+--------------+------------+
|    Column    |   DataType   | Attributes |
+--------------+--------------+------------+
| Id           | INT          | PK         |
| Culture_Code | NVARCHAR(10) |            |
+--------------+--------------+------------+

Lookup_t9n

+----------------+---------------+---------------------+
|     Column     |   DataType    |     Attributes      |
+----------------+---------------+---------------------+
| Id             | INT           | PK                  |
| Culture_Id     | INT           | FK to Culture table |
| Localised_Text | NVARCHAR(MAX) |                     |
+----------------+---------------+---------------------+

如您所见，我有一个查找表，其中存储了所有查找.查找的显示文本已本地化并存储在单独的表中.该表具有文化表的外键，以指示本地化文本所在的文化.

As you can see, I have a lookup table where all lookups are stored. The display text for a lookup is localized and stored in a separate table. This table has a foreign key to culture table to indicate the culture for which the localized text exists.

我的班级是这样的

public class Lookup {

    public virtual int Id {get; set;}

    public virtual string Code {get; set;}

    public virtual string DisplayText {get; set;}
}

我的 FNH 映射类看起来像这样

And my FNH mapping class looks like this

public class LookupMappings : ClassMap<Lookup> {

    public LookupMappings()
    {
        Table("Lookup");
        Id(x => x.Id).Column("Id");
        Map(x => x.Code).Column("Code");

        Join("Lookup_t9n", join => {
            join.Map(x => x.DisplayText).Column("Localised_Text"); //Note this place, my problem is here
        })
    }
}

在上面的映射中，在 Join 部分，我想提供一些 where 子句，例如 WHERE Lookup_t9n.Culture_Id = Culture.Culture_Id AND Culture.Culture_Code = System.Threading.Thread.CurrentUICulture.文化代码.

In the above mapping, in Join part I want to provide some where clause like WHERE Lookup_t9n.Culture_Id = Culture.Culture_Id AND Culture.Culture_Code = System.Threading.Thread.CurrentUICulture.CultureCode.

我知道这不是一个有效的 SQL，但传达了我希望的意图.有没有人有做这样的事情的经验.

I know this is not a valid SQL but conveys the intent I hope. Has anyone have any experience of doing such a thing.

我可以添加一个映射层，我可以在其中拥有与数据库表一对一映射的类，然后编写普通的 c# 将这些类映射回我的 Lookup 类.我宁愿这样做作为临时解决方案.我想知道我是否可以通过一些巧妙的 NH 使用来删除该映射层.

I can add a mapping layer where I can have classes that map one-to-one with database tables and then write plain c# to map those classes back to my Lookup class. I have rather done that as an interim solution. I was wondering if I can remove that mapping layer with some smart NH use.

推荐答案

我没有简单的答案，比如CallThis().我想根据我们如何使用类似的东西给你建议.该解决方案基于标准映射，将其复杂性隐藏在 C# 实体中.这只是解决方案的草稿，所以我将跳过中间的 Culture 表，并期望在 Lookup_t9n 中我们只存储一个区域性名称(en，cs...)

I do not have simple answer, like CallThis(). I would like to give you suggestion, based on how we are using similar stuff. The solution is base on the standard mapping, hidding its complexity in C# Entities. It is just a draft of the solution so I'll skip the middle Culture table, and will expect that in Lookup_t9n we do store just a culture name (en, cs...)

我们来上课

public class Lookup {
    public virtual int Id {get; set;}
    public virtual string Code {get; set;}
                                     // for simplicity skipping null checks    
    public virtual DisplayText { get { return Localizations.First().LocalizedText; } } 
    public virtual IList<Localization> Localizations {get; set;}
}

public class Localization { // mapped to Lookup_t9n
    public virtual string CultureName {get; set;}
    public virtual string LocalizedText {get; set;}
}

有了这个，我们可以将 Localizations 的 collection 映射为 HasMany.它甚至可以映射为组件(参见组件映射示例)

Having this, we can map the collection of Localizations as HasMany. It could even be mapped as a component (see example of component mapping)

现在，我们需要引入一个过滤器.Fluent 示例.基本文档:18.1.NHibernate 过滤器.

Now, what we do need is to introduce a filter. Example with Fluent. The essential documentation: 18.1. NHibernate filters.

简化映射

过滤器:

public class CulturFilter : FilterDefinition
{
  public CulturFilter()
  {
    WithName("CulturFilter")
        .AddParameter("culture",NHibernate.NHibernateUtil.String);
  }

集合:

HasMany(x => x.Localization)
    .KeyColumn("Id")
    ...
    .ApplyFilter<CulturFilter>("CultureName = :culture"))
    .Cascade.AllDeleteOrphan();

最后，我们要引入一些AOP过滤器，IInterceptor...每次都会触发(需要)并调整ISession

Finally, we have to introduce some AOP filter, IInterceptor... which will be triggered each time (needed) and adjust the ISession

session
   .EnableFilter("CulturFilter")
   .SetParameter("culture"
     ,System.Globalization.CultureInfo.CurrentCulture.TwoLetterISOLanguageName);

现在我们有了基于当前文化的Localized字符串，同时使用本地化值的标准映射作为集合.

And now we have Localized string based on current culture, while using standard mapping of localized values as a collection.

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