难以映射与NHibernate的关系

Question

我正在使用2个表，Employees和一个名为EmployeeGroups的表，如下所示。我省略了下面大多数不相关的专栏。我正在努力映射外键关系。我想知道如何在下面的映射文件中设置EmployeeId关系？

员工

CREATE TABLE [dbo].[Employees](
[EmployeeId] [int] IDENTITY(1,1) NOT NULL,
[ForeName] [nvarchar](20) COLLATE Latin1_General_CI_AI NOT NULL,
[SurName] [nvarchar](20) COLLATE Latin1_General_CI_AI NOT NULL,

CONSTRAINT [PK_Employees_1] PRIMARY KEY CLUSTERED 
(
    [EmployeeId] ASC
)WITH (IGNORE_DUP_KEY = OFF) ON [PRIMARY]
) ON [PRIMARY]

EmployeeGroups

CREATE TABLE [dbo].[EmployeeGroups](
[GroupId] [int] NULL,
[EmployeeId] [int] NOT NULL,
[Active] [int] NULL,
 CONSTRAINT [PK_EmployeeGroups] PRIMARY KEY CLUSTERED 
(
    [EmployeeId] ASC
)WITH (IGNORE_DUP_KEY = OFF) ON [PRIMARY]
) ON [PRIMARY]

USE [DemoDEV]
GO
ALTER TABLE [dbo].[EmployeeGroups]  WITH CHECK ADD  CONSTRAINT     
[FK_EmployeeGroups_Employees] FOREIGN KEY([EmployeeId])
REFERENCES [dbo].[Employees] ([EmployeeId])

到目前为止，我的员工映射文件

<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2">
<class name="AdaptiveMaintenance.Core.Domain.Employee, AdaptiveMaintenance.Core" table="Employees" lazy="false">
    <id name="ID" column="EmployeeId">
        <generator class="assigned" />
    </id>
    <property name="Forename" column="ForeName" not-null="true"/>
    <property name="Surname" column="SurName" not-null="true"/>

</class>
</hibernate-mapping>

到目前为止，我的EmployeeGroups映射文件如下所示

<?xml version="1.0" encoding="utf-8" ?>
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2">
  <class name="AdaptiveMaintenance.Core.Domain.EmployeeGroup, AdaptiveMaintenance.Core" table="EmployeeGroups" lazy="false">
      <id name="ID" column="EmployeeId">
      <generator class="foreign" />
    </id>

    <property name="Active" column="Active" />
</class>

​

Answer 1

您不仅应该考虑如何映射db模型，还应该始终考虑类模型:它应该是什么样子的？

这将创建一个从EmployeeGroup到Employee的引用。

<?xml version="1.0" encoding="utf-8" ?>
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2">
  <class name="AdaptiveMaintenance.Core.Domain.EmployeeGroup, AdaptiveMaintenance.Core" table="EmployeeGroups" lazy="false">
    <id name="ID" column="GroupId">
      <generator class="assigned" />
    </id>

    <property name="Active" column="Active" />
    <many-to-one name="Employee" class="Employee" column="EmployeeId"/>
</class>

当你有一个一对一的关系并尝试耦合主键时，为什么会有一个GroupId？我让它成为一个独立的主键。

顺便说一句，如果你正在创建一个新的数据库模型，首先设计类，然后映射它们，然后使用SchemaExport创建模式，这会更容易。