NHibernate xml 继承子类找不到列

Question

我是第一次使用 NHibernate。我有一个 table 每个 class 层次结构（抽象超级 class）。当我尝试保存 subclass（学生）时，我收到错误消息：

[SqlException (0x80131904): Invalid column name 'Firstname' etc...]

我的 HBM 文件：

    <hibernate-mapping xmlns="urn:nhibernate-mapping-2.2"
                   assembly="xx"
                   namespace="xx.Models">
  <class name="User" table="[User]" lazy="false">
    <id name="UserID" column="UserID">
      <generator class="native" />
    </id>
    <discriminator column="Type" type="String"/>

    <property name="Email" column="Email" />

    <subclass name="Student" discriminator-value="0">
      <property name="Firstname" column="Firstname" />
    </subclass>

    <subclass name="Company" discriminator-value="1">
      <property name="Name" column="Name" />
    </subclass>

  </class>
</hibernate-mapping>

SQL代码：

CREATE TABLE [dbo].[User] (
UserID                  INT             NOT NULL IDENTITY(1,1),
Type                    CHAR(1)         NOT NULL,
Email                   VARCHAR(255)    NOT NULL,
PRIMARY KEY(UserID)
);

CREATE TABLE [dbo].[Student] (
UserID                  INT             NOT NULL,
Firstname               VARCHAR(255)    NOT NULL,
PRIMARY KEY(UserID),
FOREIGN KEY(UserID) REFERENCES [User](UserID)               
);

CREATE TABLE [dbo].[Company] (
UserID                  INT             NOT NULL,
Name                    VARCHAR(255)    NOT NULL,
PRIMARY KEY(UserID),
FOREIGN KEY(UserID) REFERENCES [User](UserID),
);

我可能缺少配置设置，数据库是 MS SQL，谁能帮帮我？

Answer 1

更新（与更新的问题相关）

简而言之，我们需要映射 <joined-subclass> 而不是 <discriminator>

重点是，我们在需要

时为8.1.1. Table per class hierarchy使用映射

8.1.2. Table per subclass

（很少引用）

A table-per-subclass mapping would look like:

<class name="IPayment" table="PAYMENT">
    <id name="Id" type="Int64" column="PAYMENT_ID">
        <generator class="native"/>
    </id>
    <property name="Amount" column="AMOUNT"/>
    ...
    <joined-subclass name="CreditCardPayment" table="CREDIT_PAYMENT">
        <key column="PAYMENT_ID"/>
        ...
    </joined-subclass>
    <joined-subclass name="CashPayment" table="CASH_PAYMENT">
        <key column="PAYMENT_ID"/>
        ...
    </joined-subclass>
    <joined-subclass name="ChequePayment" table="CHEQUE_PAYMENT">
        <key column="PAYMENT_ID"/>
        ...
    </joined-subclass>
</class>

Four tables are required. The three subclass tables have primary key associations to the superclass table (so the relational model is actually a one-to-one association).

与此类似，我们需要这样的映射：

<class name="User" table="[User]" lazy="false">
    <id name="UserID" column="UserID">
      <generator class="native" />
    </id>

    <joined-subclass name="Sutdent" table="Student">
       <key column="UserID"/>
       <property name="Firstname" column="Firstname" />
       ...
    </joined-subclass>

</class>

原始部分（与原始问题相关）

在这种情况下，错误应该非常清楚：缺少列 'Firstname'。因为使用 table 每个 class 层次结构 我们只需要在我们的 table 中包含所有列。每个完整的层次结构是一个 table。没有其他 place/table 可以保存数据的地方...

8.1.1. Table per class hierarchy

Exactly one table is required. There is one big limitation of this mapping strategy: columns declared by the subclasses may not have NOT NULL constraints.

万一您问：NHibernate 如何为我更新数据库模式？ 请检查：

How to update database table schemas with NHibernate schema generation?

（小摘录，详见上文link）

Configuration cfg ...
cfg.Configure();
...
var update = new SchemaUpdate(cfg);
update.Execute(true, false);

NHibernate xml 继承子类找不到列

NHibernate xml inheritance subclass could not find column

sql-server

xml

nhibernate

subclass

nhibernate-mapping

8.1.2. Table per subclass

How to update database table schemas with NHibernate schema generation?