使用 NHibernate 使用外键从 MySQL table 获取数据

Question

我有一个 MySQL 数据库，其中包含 table 树：作者、出版社和书籍。最后一个有两个外键 - AuthorId 和 PublishingId。我为每个 table 制作了类并为 NHibernate 制作了一个映射文件。下一点是从 Book table 中获取数据并将其传递到我的 MVC 项目的视图中。我不能这样做，因为在我的 BookController 中我遇到了这样的异常： NHibernate.PropertyAccessException: Invalid Cast (check your mapping for property type mismatches);

这是我现在的代码：

型号

public class Author
{
    public virtual int Id { get; set; }
    public virtual string FirstName { get; set; }
    public virtual string LastName { get; set; }
}

public class PublishingHouse
    {
        public virtual int Id { get; set; }
        public virtual string Name { get; set; }
        public virtual string City { get; set; }

    }

public class Book
    {
        public virtual int Id { get; set; }
        public virtual string UDK { get; set; }
        public virtual string BBK { get; set; }

        public virtual string AuthorsSign { get; set; }
        public virtual string ISBNrus { get; set; }
        public virtual string ISBNeng { get; set; }

        public virtual Author Author { get; set; }
        public virtual string Name { get; set; }
        public virtual PublishingHouse PublishingHouse { get; set; }

        public virtual int Year { get; set; }
        public virtual int Pages { get; set; }
        public virtual int Circulation { get; set; }

        public virtual bool IsRead { get; set; }
        public virtual int Rating { get; set; }
        public virtual string Annotation { get; set; }
    }

NHibernate 映射

<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2" auto-import="true" assembly="InFolio_HomeLib" namespace="InFolio_HomeLib.Models">
  <class name="Author" table="Author" dynamic-update="true" >
    <cache usage="read-write"/>
    <id name="Id" column="Id" type="int">
      <generator class="native" />
    </id>
    <property name="FirstName" />
    <property name="LastName" />
  </class>

  <class name="PublishingHouse" table="PublishingHouse" dynamic-update="true" >
    <cache usage="read-write"/>
    <id name="Id" column="Id" type="int">
      <generator class="native" />
    </id>
    <property name="Name" />
    <property name="City" />
  </class>

    <class name="Book" table="Book" dynamic-update="true" >
    <cache usage="read-write"/>
    <id name="Id" column="Id" type="int">
      <generator class="native" />
    </id>
    <property name="UDK" />
    <property name="BBK" />
    <property name="AuthorsSign" />
    <property name="ISBNrus" />
    <property name="ISBNeng" />   

    <set name="Author" table="Author">
      <key column ="Id" />
      <one-to-many class="Author"/>
    </set>    

    <property name="Name" /> 

    <set name="PublishingHouse" table="PublishingHouse">
      <key column ="Id" />
      <one-to-many class="PublishingHouse"/>
    </set>    

    <property name="Year" />
    <property name="Pages" />
    <property name="Circulation" />
    <property name="IsRead" />
    <property name="Rating" />
    <property name="Annotation" />
  </class>
</hibernate-mapping>

BookController 我得到一个异常：

    public ActionResult Index()
    {
        using (ISession connectionDB = NHibertnateSession.OpenSession())
        {
            var books = connectionDB.Query<Book>().ToList();
            return View(books);
        }
    }

我可以很容易地从 Author 和 Publishing table 获取数据，它们很简单，但是 Book table 对我来说不是那么明显。我在映射中错了吗？或者其他地方？

Answer 1

本书class

<class name="Book" table="Book" dynamic-update="true" >

有一位作者和一家出版社。我们需要many-to-one映射

所以，而不是这个：

<set name="Author" table="Author">
  <key column ="Id" />
  <one-to-many class="Author"/>
</set>    

<set name="PublishingHouse" table="PublishingHouse">
  <key column ="Id" />
  <one-to-many class="PublishingHouse"/>
</set>

我们需要：

<many-to-one name="Author" column="Author_ID" />
<many-to-one name="PublishingHouse" column="PublishingHouse_ID" />

希望图书 table 具有参考列 Author_ID 和 PublishingHouse_ID

文档：

5.1.11. many-to-one

An ordinary association to another persistent class is declared using a many-to-one element. The relational model is a many-to-one association. (It's really just an object reference.) ...

另外，不要错过这个：

使用 NHibernate 使用外键从 MySQL table 获取数据

Get data from MySQL table with foreign keys using NHibernate

mysql

nhibernate

5.1.11. many-to-one