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

---

转载请注明出处

示例代码基于nHibernate3.3.1