Question

我有以下表和实体需要在Fluent NHibernate中映射。

表：

CREATE TABLE workarea
(
  id uuid NOT NULL,
  name character varying(255) NOT NULL,
  CONSTRAINT pk_workarea PRIMARY KEY (id),
)

CREATE TABLE element
(
  id uuid NOT NULL,
  name character varying(255) NOT NULL,
  CONSTRAINT pk_element PRIMARY KEY (id),
)

CREATE TABLE attachment
(
  id uuid NOT NULL,
  filename character varying(255) NOT NULL,
  CONSTRAINT pk_attachment PRIMARY KEY (id),
)  

CREATE TABLE objectattachment
(
  id uuid NOT NULL,
  attachmentid uuid NOT NULL,
  attachmenttype string NOT NULL,
  objectid uuid NOT NULL,
  CONSTRAINT pk_objectattachment PRIMARY KEY (id),
  CONSTRAINT fk_oa_a FOREIGN KEY (attachmentid)
      REFERENCES attachment (id) MATCH SIMPLE
      ON UPDATE RESTRICT ON DELETE RESTRICT,
  CONSTRAINT fk_oa_at FOREIGN KEY (attachmenttypeid)
      REFERENCES attachmenttype (id) MATCH SIMPLE
      ON UPDATE RESTRICT ON DELETE RESTRICT
)

此数据库设计下的想法如下：

“工作区”或“元素”可能有多个“附件”文件，“附件”文件可能会由多个“工作区”或“元素”引用。
“工作区”或“元素”可以指同一个“附件”文件。

所以“附件”和“工作区”或“元素”之间的关系存储在“对象附件”中 “表，其中：

“attachmentid”字段是指特定“附件”的标识符。
“attachmenttype”字段（discriminator）定义了这种关系在“附件”和“工作区”之间或“附件”和“附件”之间 “元件” 第
“objectid”字段是指特定“工作区”或“元素”的标识符，具体取决于上述“attachmenttype”字段的值。

基于数据库设计，我然后按如下方式定义域模型类：

public class WorkArea    
{
     private Guid _id = Guid.Empty;
     private string _name;
     public virtual Guid Id     
     {
          get { return _id ; }
          set { _id = value; }
     }
     public virtual string Name     
     {
          get { return _name ; }
          set { _name = value; }
     }
}

public class Element    
{
     private Guid _id = Guid.Empty;
     private string _name;
     public virtual Guid Id     
     {
          get { return _id ; }
          set { _id = value; }
     }
     public virtual string Name     
     {
          get { return _name ; }
          set { _name = value; }
     }
}

public class Attachment
{
     private Guid _id = Guid.Empty;
     private string _fileName;
     public virtual Guid Id     
     {
          get { return _id ; }
          set { _id = value; }
     }
     public virtual string FileName     
     {
          get { return _fileName; }
          set { _fileName= value; }
     }
}

public class WorkAreaAttachment : Attachment
{
     private WorkArea _workArea;
     public virtual WorkArea WorkArea 
     {
          get { return _workArea; }
          set { _workArea = value; }
     }     
}

public class ElementAttachment : Attachment
{
     private Element _element;
     public virtual Element Element
     {
          get { return _element; }
          set { _element = value; }
     }     
}

现在我的问题是我是否可以使用上述数据库设计映射这些域模型类。如果是，那我怎么能这样做？如果不是，那么如何更改域模型类以支持针对设计数据库的Fluent NHibernate映射，因为我不想更改当前数据库设计（即为“workarea”和“element”创建单独的“附件”表）

此致泉

Answer 1

public class AttachmentLink
{
     private Attachment _attachment;
     public virtual Attachment Parent
     {
          get { return _attachment; }
          set { _attachment = value; }
     }

     private IHasAttachments _linkedTo;
     public virtual IHasAttachments LinkedTo
     {
          get { return _linkedTo; }
          set { _linkedTo = value; }
     }
}

// in AttachmentMap
HasMany(x => x.Links)
    .Table("objectattachment");

// map the component
sealed class AttachmentLinkMap : ComponentMap<AttachmentLink>
{
    public AttachmentLinkMap()
    {
        References(x => x.Attachment, "attachmentid");
        ReferencesAny(x => x.LinkedTo)
            .IdentityType<Guid>()
            .EntityIdentifierColumn("objectid")
            .EntityTypeColumn("attachmenttype")
            .AddMetaValue<WorkArea>(typeof(WorkArea).Name.ToLower())
            .AddMetaValue<Element>(typeof(Element).Name.ToLower())
            .Not.LazyLoad();  // to prevent false proxies
    }
}


// in ElementMap, and almost the same in WorkAreaMap
HasManyToMany(x => x.Attachments)
    .Where("attachmenttype='element'")

注意：您不需要链接表中的Id列

流利的NHibernate：如何使用鉴别器映射多对多关系

1 个答案: