Question

我正在尝试重用现有的映射并以各种方式扩展它们。

假设你有这张表：

create table entity (
    id int identity(1,1) not null,
    a varchar(max) not null,
    b int not null,
    c int not null
    constraint pk_entity primary key clustered (id asc))

这些实体：

  public class Entity
  {
    public virtual int ID { get; set; }

    public virtual string A { get; set; }

    public override string ToString()
    {
      return string.Format("{{{0} {1}: {2}}}", GetType().Name, ID, A);
    }
  }

  public class EntityExt1 : Entity
  {
    public virtual int B { get; set; }

    public override string ToString()
    {
      return string.Format("{{{0} {1}: {2} {3}}}", GetType().Name, ID, A, B);
    }
  }

  public class EntityExt2 : Entity
  {
    public virtual int C { get; set; }

    public override string ToString()
    {
      return string.Format("{{{0} {1}: {2} {3}}}", GetType().Name, ID, A, C);
    }
  }

这是映射：

<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2"
                   assembly="FunWithNHibernateSubclassMappings"
                   namespace="FunWithNHibernateSubclassMappings">

  <class name="Entity" table="entity">

    <id name="ID" column="id">
      <generator class="identity" />
    </id>

    <property name="A" column="a" type="string" />

  </class>

</hibernate-mapping>

这是进行测试的程序：

using System;
using System.Linq;
using System.Reflection;
using NHibernate.ByteCode.LinFu; // NuGet console: install-package NHibernate.LinFu 
using NHibernate.Cfg;
using NHibernate.Cfg.Loquacious;
using NHibernate.Dialect;
using NHibernate.Linq;
using NHibernate;

namespace FunWithNHibernateSubclassMappings
{
  public class Program
  {
    static string CONNSTRING = "Data Source=127.0.0.1;Initial Catalog=testdb;User Id=developer;Password=secret";

    static ISession OpenSession(string connectionString)
    {
      Configuration config = (new Configuration())
        .DataBaseIntegration(x =>
        {
          x.Dialect<MsSql2008Dialect>();
          x.ConnectionString = connectionString;
          x.LogFormatedSql = true;
          x.LogSqlInConsole = true;
        })
        .Proxy(x =>
        {
          x.ProxyFactoryFactory<ProxyFactoryFactory>();
        })
        .AddAssembly(Assembly.GetExecutingAssembly());

      ISessionFactory sessionFactory = config.BuildSessionFactory();

      return sessionFactory.OpenSession();
    }

    static void Main(string[] args)
    {
      ISession session = OpenSession(CONNSTRING);

      Console.WriteLine("Query 1:");
      session.Query<Entity>()
        .Where(j => j.A == "Albatross")
        .ToList()
        .ForEach(Console.WriteLine);

      Console.WriteLine("Query 2:");
      session.Query<EntityExt>()
        .Where(j => j.A == "Albatross")
        .ToList()
        .ForEach(Console.WriteLine);

      Console.WriteLine();
      Console.WriteLine("That's all, folks!");
      Console.ReadLine();
    }
  }
}

然后，实体的映射可以包含各种有用的知识，例如如何映射到其他表。 EntityExt1和EntityExt2实体和映射将受益于能够使用该知识，因为它们不需要重复什么是主键，什么是基本属性以及与其他实体的关系。

让每个开发人员只更改Entity的现有映射并不好，因为向另一个实体添加关系可能会改变现有代码的行为，从而增加测试人员的负担。

有没有办法用NHibernate做到这一点？

扩展现有的NHibernate映射

0 个答案: