使用NHibernate和EAV数据模型

Question

我正在尝试利用NH来映射到数据模型,这是对EAV/CR数据模型的宽松解释.

我有大部分工作,但我正在努力映射Entity.Attributes集合.

以下是有问题的表格:

--------------------
| Entities         |
--------------------
| EntityId  PK     |-|
| EntityType       | |
-------------------- |
         -------------
         |
         V
--------------------
| EntityAttributes |    ------------------    ---------------------------
--------------------    | Attributes     |    | StringAttributes        |
| EntityId  PK,FK  |    ------------------    ---------------------------
| AttributeId  FK  | -> | AttributeId PK | -> | StringAttributeId PK,FK |
| AttributeValue   |    | AttributeType  |    | AttributeName           |
--------------------    ------------------    ---------------------------

AttributeValue列实现为sql_variant列,我为它实现了NHibernate.UserTypes.IUserType.

我可以创建一个EntityAttribute实体并直接保存它,以便部分层次结构正常工作.

我只是不确定如何将EntityAttributes集合映射到Entity实体.

请注意,EntityAttributes表可以(并且确实)包含给定EntityId/AttributeId组合的多个行:

EntityId AttributeId AttributeValue
-------- ----------- --------------
1        1           Blue
1        1           Green

对于此示例,StringAttributes行如下所示:

StringAttributeId AttributeName
----------------- --------------
1                 FavoriteColor

如何有效地将此数据模型映射到我的Entity域,以便Entity.Attributes("FavoriteColors")返回喜欢的颜色集合？输入为System.String？

Answer 1

开始

class Entity
{
    public virtual int Id { get; set; }

    internal protected virtual ICollection<EntityAttribute> AttributesInternal { get; set; }

    public IEnumerable<T> Attributes<T>(string attributeName)
    {
        return AttributesInternal
            .Where(x => x.Attribute.Name == attributeName)
            .Select(x => x.Value)
            .Cast<T>();
    }
}

class EntityAttribute
{
    public virtual Attribute Attribute { get; set; }

    public virtual object Value { get; set; }
}

class EntityMap : ClassMap<Entity>
{
    public EntityMap()
    {
        HasMany(e => e.AttributesInternal)
            .Table("EntityAttributes")
            .KeyColumn("EntityId")
            // EntityAttribute cant be an Entity because there is no real Primary Key
            // (EntityId, [AttributeId] is not unique)
            .Component(c =>
            {
                c.References(ea => ea.Attribute, "AttributeId").Not.LazyLoad();
                c.Map(ea => ea.Value, "AttributeValue").CustomType<VariantUserType>();
            });
    }
}