nHibernate Mapping By Code - Introduction

nHibernate 3.2新增了一种mapping by code的映射策略，很有意思。你可以自定义约定，并且按照约定定制自动映射策略，面对遗留数据库时这个功能往往很有用，另外，由于mapping by code是基于代码的（而不是xml文件），对domain object进行重命名的重构操作会非常方便，不用跑到xml映射文件查找字符串了。

要使用Mapping by Code很简单，

第一步，配置SessionFactory，使nhibernate自动扫描项目中所有继承ClassMapping的类，并将其解释为映射

public class NHibernateHelper
{private static ISessionFactory _sessionFactory;public static ISessionFactory SessionFactory{get{if (_sessionFactory == null){var configuration = new Configuration();configuration.Configure();var mappers = new ModelMapper();mappers.AddMappings(Assembly.GetExecutingAssembly().GetExportedTypes());var hbmMapping = mappers.CompileMappingForAllExplicitlyAddedEntities();Console.WriteLine(hbmMapping.AsString());configuration.AddDeserializedMapping(hbmMapping, "");_sessionFactory = configuration.BuildSessionFactory();}return _sessionFactory;}}public static ISession OpenSession(){return SessionFactory.OpenSession();}
}

 

第二步，为每个实体类编写映射类，映射类只需继承ClassMapping就可以被nhibernate识别。

关于如何编写映射类，参考以下文章：

nHibernate Mapping By Code - One to One

nHibernate Mapping By Code - One to Many and Many to One

nHibernate Mapping By Code - Many to Many

参考文章：

NH Mapping by code VS the Untouchable DB

Using NH3.2 mapping by code for Automatic Mapping

NHibernate剖析：Mapping篇之Mapping-By-Code(2):运用ModelMapper

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示例代码基于nHibernate3.3.1