使用NHibernate从带有外键的MySQL表中获取数据 [英] Get data from MySQL table with foreign keys using NHibernate
问题描述
我有一个带有树表的MySQL数据库:作者,出版社和书.最后一个有两个外键-AuthorId和PublishingId.
我为每个表创建了类,并为NHibernate创建了映射文件.
接下来的一点是从Book表中获取数据,并将其传递给我的MVC项目的View.
我无法执行此操作,因为在BookController中,我遇到了如下异常:
NHibernate.PropertyAccessException: Invalid Cast (check your mapping for property type mismatches);
I have a MySQL database with tree tables: Author, PublishingHouse and Book. The last one has two foreign keys - AuthorId and PublishingId.
I've made classes for each table and a mapping file for NHibernate.
The next point is to get data from Book table and pass it to the View of my MVC project.
I can't do this, because in my BookController I got an exception like this:
NHibernate.PropertyAccessException: Invalid Cast (check your mapping for property type mismatches);
这是我现在的代码:
模型
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 ,这里出现异常:
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表中获取数据,它们很简单,但是Book表对我而言并不那么明显.我在映射上错了吗?还是其他地方?
I can easy get data from Author and Publishing tables, they are quite simple, but Book table is not so obvious for me. Am I wrong in mapping? Or somewhere else?
推荐答案
Book类
<class name="Book" table="Book" dynamic-update="true" >
有一位作家和一间出版社.我们需要多对一映射
has one author and one publishing house. We need many-to-one mapping
所以,代替这个:
<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" />
期望Book表具有参考列Author_ID和PublishingHouse_ID
Expecting the Book table to have reference columns Author_ID and PublishingHouse_ID
文档:
5.1.11.多对一
使用以下方法声明与另一个持久类的普通关联 多对一元素.关系模型是多对一的 协会. (它实际上只是一个对象引用.)...
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.) ...
此外,请不要错过:
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