从IoC开始说起
博主最早开始用的IoC容器叫AutoFac,那时候用它主要是为了生命周期管理——将EF上下文的生命周期限定为每请求。当然也总是每每听到IoC的好处,但是仍然不能理解其优势。最近在学习和实现Cqrs的时候,却是有了明显的体会了。我们以前分层的时候,用的Service和Reponsitory。通常的情形是:Service需要访问一些数据,就得在Reponsitory中添加一些方法,否则无法完成。往往这是很困惑的,Service经常成了Reponsitory的简单的包装。同时,Service是依赖于Reponsitory的,仓储提供了什么,服务才能继续做什么。同时——模型是被仓储引用的,也就是模型不是和Service紧密关联的。我们也尝试过将仓储和服务提取为接口,然而并没有直观的改善——因为我们依赖关系没有变(仓储接口<-仓储<-服务接口<-服务)。学习CQRS的时候,曾经看过一些例子,模型是和业务紧密结合的。当时博主用自己的依赖关系代入进去发现行不通。细看才发现,仓储的接口是和服务定义在一起的(因为只有服务会/允许调用这个)。仓储的实现引用了服务,实现了仓储接口。这个时候,情形变为了:服务去要求仓储实现这些方法。依赖关系为:(模型<-仓储接口<-服务)<-仓储实现。这里引出的问题是,服务本身是不清楚具体实现是哪个的,需要调用方来指定,IoC容器就起了这个作用,通过注册,可以为特定的接口指派特定的实现。
时过境迁,由于总总原因,博主现在开始使用Unity作为容器了。
仓储与QueryEntry
就博主目前对CQRS的理解而言,实现CQRS的一个目标是从架构上将数据的查询和提交分离。所以引入了一个QueryEntry,查询入口。查询入口也需要仓储支持,且具有更多的灵活性,比如对于SQL而言,直接提交SQL查询以改善联查性能。为了实现好的隔离性,查询入口也通过接口定义。在目前的处理中,QueryEntry和Reponsitory的接口放在同一层(领域层),其实现放在同一层(Storage层)。这样,如果针对SQL,那么特殊的查询使用SQL语句完成,如果针对Oracle就使用Oracle的查询语句完成。而任何实现了这些接口的DLL都可以替换原有的DLL,领域层就不关心持久化的事情了。
其实也考虑过QueryEntry直接使用实现类来处理,但是这样的话,仓储就要暴露给应用程序层(web)。
配置
在整个解决方案中,博主使用一个Configuration项目来配置各个组件(实现)的关系,这好比是前面博文中的Configuration类的放大。为了独立管理配置,所以引入了一个扩展类,将Unity的各种配置按照语义具体化。
public class ComponentContainer { protected UnityContainer Container = new UnityContainer(); public UnityContainer GetContainer() { return Container; } //public static ComponentContainer Config() //{ // return new ComponentContainer(); //} public T Construct<T>() { return Container.Resolve<T>(); } public T Construct<T>(Type registedType) { return (T) Container.Resolve(registedType); } public void Use<T, TI>(LifetimeManager manager = null) where TI : T { if (manager == null) { Container.RegisterType<T, TI>(); } else { Container.RegisterType<T, TI>(manager); } } public void Use<T>(Type iType, LifetimeManager manager = null) { if (manager == null) { Container.RegisterType(typeof (T), iType); } else { Container.RegisterType(typeof(T), iType, manager); } } public void Use(Type type, Type iType, LifetimeManager manager = null) { if (manager == null) { Container.RegisterType(type, iType); } else { Container.RegisterType(type, iType, manager); } } public void UseInstance<T, TI>() where TI : T, new() { var instance = new TI(); Container.RegisterInstance(typeof (T), instance); } public void SpecifyLifeTime<T>(LifetimeManager manager = null) { SpecifyLifeTime(typeof (T), manager); } public void SpecifyLifeTime(Type type, LifetimeManager manager = null) { if (manager == null) { Container.RegisterType(type); } else { Container.RegisterType(type); } } }
总的来数,Unity会被解决方案中的所有项目引用。而在所有的组件中,有以下几个需要通过IoC配置:ICommandBus(单例),IEventBus(单例),仓储,QueryEntry(查询入口)...,在CQRS层的Configuration名称空间下添加以下接口表示配置支持:
public interface ICommandHandlerRegister { void RegisterCommandHandlers(ComponentContainer container); } public interface IEventHandlerRegister { void RegisterEventHandlers(ComponentContainer container); } public interface IQueryEntryRegister { void RegisterQueryEntries(ComponentContainer container); } public interface IStorageRegister { void RegisterReponsitories(ComponentContainer container); /*在这里完成工作单元的映射*/ void RegisterUnitOfWork(ComponentContainer container); }
/*为流畅接口定义的扩展,配置语义化*/ public static class FluentConfiguration { public static CqrsConfigurationResolver ConfigLifetimeManager<T>(this CqrsConfigurationResolver resolver, LifetimeManager manager) { if (resolver == null) throw new ArgumentNullException("resolver"); resolver.SpecifyLifeTime(typeof (T), manager); return resolver; } public static CqrsConfigurationResolver UseEventBus<T>(this CqrsConfigurationResolver resolver) where T : IEventBus { if (resolver == null) throw new ArgumentNullException("resolver"); /*生命周期与容器的生命周期保持一致,故而实现了单例*/ resolver.Use<IEventBus, T>(new ContainerControlledLifetimeManager()); return resolver; } public static CqrsConfigurationResolver UseCommandBus<T>(this CqrsConfigurationResolver resolver) where T : ICommandBus { if (resolver == null) throw new ArgumentNullException("resolver"); resolver.Use<ICommandBus, T>(new ContainerControlledLifetimeManager()); return resolver; } public static CqrsConfigurationResolver UseEventHandlerProvider<T>(this CqrsConfigurationResolver resolver) where T : IEventHandlerProvider { if (resolver == null) throw new ArgumentNullException("resolver"); resolver.Use<IEventHandlerProvider, T>(new ContainerControlledLifetimeManager()); return resolver; } public static CqrsConfigurationResolver UseCommandHandlerProvider<T>(this CqrsConfigurationResolver resolver) where T : ICommandHandlerProvider { if (resolver == null) throw new ArgumentNullException("resolver"); resolver.Use<ICommandHandlerProvider, T>(new ContainerControlledLifetimeManager()); return resolver; } public static CqrsConfigurationResolver UseStorageRegister<T>(this CqrsConfigurationResolver resolver) where T : IStorageRegister, new() { if (resolver == null) throw new ArgumentNullException("resolver"); var register = new T(); register.RegisterReponsitories(CqrsConfigurationResolver.Config); register.RegisterUnitOfWork(CqrsConfigurationResolver.Config); return resolver; } public static CqrsConfigurationResolver UseCommandHandlerRegister<T>(this CqrsConfigurationResolver resolver) where T : ICommandHandlerRegister, new() { if (resolver == null) throw new ArgumentNullException("resolver"); var register = new T(); register.RegisterCommandHandlers(CqrsConfigurationResolver.Config); return resolver; } public static CqrsConfigurationResolver UseEventHandlerRegister<T>(this CqrsConfigurationResolver resolver) where T : IEventHandlerRegister, new() { if (resolver == null) throw new ArgumentNullException("resolver"); var register = new T(); register.RegisterEventHandlers(CqrsConfigurationResolver.Config); return resolver; } public static CqrsConfigurationResolver UseQueryEntryRegister<T>(this CqrsConfigurationResolver resolver) where T : IQueryEntryRegister, new() { if (resolver == null) throw new ArgumentNullException("resolver"); var register = new T(); register.RegisterQueryEntries(CqrsConfigurationResolver.Config); return resolver; } public static CqrsConfigurationResolver UseAuditingStore<T>(this CqrsConfigurationResolver resolver) where T : IAuditingStore, new() { if (resolver == null) throw new ArgumentNullException("resolver"); resolver.Use<IAuditingStore,T>(); return resolver; } public static CqrsConfigurationResolver UseAuditingConfiguration<T>(this CqrsConfigurationResolver resolver) where T : IAuditingConfiguration, new() { if (resolver == null) throw new ArgumentNullException("resolver"); resolver.Use<IAuditingConfiguration, T>(); return resolver; } public static CqrsConfigurationResolver UseUnitOfWork<T>(this CqrsConfigurationResolver resolver) where T : IUnitOfWork { if (resolver == null) throw new ArgumentNullException("resolver"); resolver.Use<IUnitOfWork, T>(new PerThreadLifetimeManager()); return resolver; } public static CqrsConfigurationResolver UseSession<T>(this CqrsConfigurationResolver resolver, LifetimeManager manager) where T : IDpfbSession { if (resolver == null) throw new ArgumentNullException("resolver"); resolver.Use<IDpfbSession, T>(manager); return resolver; } public static CqrsConfigurationResolver UseAuditInfoProvider<T>(this CqrsConfigurationResolver resolver) where T : IAuditInfoProvider { if (resolver == null) throw new ArgumentNullException("resolver"); resolver.Use<IAuditInfoProvider, T>(); return resolver; } }
这里是一个调用的例子:
public static class ConfigurationInitializer { public static void Initial() { CqrsConfigurationResolver.Config .UseCommandBus<DpfbCommandBus>() .UseEventBus<DpfbEventBus>() .UseCommandHandlerProvider<InterfaceBasedCommandHandlerProvider>() .UseEventHandlerProvider<InterfaceBasedEventHandlerProvider>() //.UseStorageRegister<FakeStorageRegister>() .UseStorageRegister<EntityFrameworkStorageRegister>() .UseQueryEntryRegister<QueryEntryRegister>() .UseCommandHandlerRegister<DefaultCommandHandlerRegister>() .UseEventHandlerRegister<DefaultEventHandlerRegister>() .UseAuditingStore<MemoryAuditingStore>() .UseAuditInfoProvider<NullAuditInfoProvider>() .UseSession<HttpDpfbSession>(new PerHttpRequestOrThreadLifetimeManager()) .UseAuditingConfiguration<EnabledAuditingConfiguration>(); } }
...
【想到什么再补充】