Enterprise Library-PIAB与Unity集成
在EnteLib中,PIAB(Policy Injection Application Block)和Unity的定位是轻量级的AOP框架和IoC容器(Container)。通过PIAB,我们可以将一些业务无关的 crosscutting concern定义于相应的CallHandler中,通过Attribute声明或者配置应用到承载业务逻辑的目标方法上。而通过Unity提供的 IoC容器(或者DI容器),即UnityContainer,很好地实现了依赖的动态注入,从而实现了组件之间、模块之间或者服务之间的松耦合。
Unity 完全建立在ObjectBuilder2之上,顾名思义,这是一个用于创建对象的基础组件。ObjectBuilder2提供了一种具有高可扩展性的、基 于策略(Strategy Based)的对象创建框架,它不仅仅是Unity的基础组件,也是整个EnterLib和Software Factory的基石。而PIAB通过方法调用劫持(Method Call Interception)的机制实现了策略注入(Policy Injection)。PIAB提供了不同的方法劫持机制,最为典型的就是基于TransparentProxy(可以参考我的PIAB系列文章) 和代码生成(比如动态生成一个继承自目标类型的子类,通过Override掉相应的Virtual方法实现策略注入;或者动态生成一个实现了目标接口的类 型,实现相应的方法实现策略注入)。PIAB需要通过特殊的机制创建可被劫持(Interceptable)对象,而UnityContainer本质上 是一个创建对象的容器,如果能够使UnityContainer按照PIAB的要求创建可被劫持(Interceptable)对象,那么就能实现两者之 间的集成。(Source Code从这里下载)
一、Unity 1.2和EnterLib 4.1如何实现两者的集成
在Enterprise Library-通过Unity Extension实现和Policy Injection Application Block的集成谈过PIAB和Unity之间的集成问题,当时我们是采用了一个自定以UnityContainerExtension实现的,当时针对的版本是 Unity 1.1和EnterLib 3.1。到了Unity 1.2和EnterLib 4.1,Unity已经被广泛地使用到了整个EnterLib内部,微软甚至通过Unity对PIAB进行了彻底的改造。所以,最新的Unity和 PIAB中,已经提供了两者的原生集成。
Unity和PIAB两者之间的集成是通过一个特殊的 UnityContainerExtension—— Microsoft.Practices.Unity.InterceptionExtension.Interception实现的。为了演示 Interception的使用,我们创建一个简单的例子。该例子中定义了一服务SyncTimeProvisionService用于实现同步时间的提 供,SyncTimeProvisionService实现了接口ISyncTimeProvision。 SyncTimeProvisionService本身并不提供具体实现,而是通过另一个组件SyncTimeProvider实现具体的同步时间的返 回,SyncTimeProvider实现接口ISyncTimeProvider。
你可以将 SyncTimeProvisionService和SyncTimeProvider看成是一个应用中具有依赖关系的两个模块,为了实现两个模块之间的 解耦,采用基于接口的依赖是推荐的设计模式。所以,SyncTimeProvisionService并不之间依赖于SyncTimeProvider, 而是依赖于SyncTimeProvider的接口ISyncTimeProvider。我们通过Constructor注入实现依赖注入。为了让读者对 Unity和PIAB集成的效果具有一个直观的印象,我在SyncTimeProvider 上应用了一个CachingCallHandlerAttribute,如果该CallHandler生效,方法执行的结果将会被缓存,在缓存过期之前,得到的时间将是一样的。相应的代码如下所示:
using System; namespace Artech.InterceptableUnity { public interface ISyncTimeServiceProvision { DateTime GetCurrentTime(); } public class SyncTimeServiceProvisionService : ISyncTimeServiceProvision { public ISyncTimeProvider SyncTimeProvider { get; private set; } public SyncTimeServiceProvisionService([Dependency]ISyncTimeServiceProvider syncTimeServiceProvider) { this.SyncTimeServiceProvider = syncTimeServiceProvider; } #region ISyncTimeServiceProvision Members public DateTime GetCurrentTime() { return this.SyncTimeProvider.GetCurrentTime(); } #endregion } public interface ISyncTimeProvider { DateTime GetCurrentTime(); } [CachingCallHandler] public class SyncTimeProvider : ISyncTimeProvider { #region ISyncTimeServiceProvider Members public DateTime GetCurrentTime() { return DateTime.Now; } #endregion } }
那么我们就可以通过下面的方式,利用UnityContainer采用基于接口(ISyncTimeServiceProvision)的方式创建SyncTimeServiceProvisionService ,并调用GetCurrentTime方法:
using System; using System.Threading; using Microsoft.Practices.EnterpriseLibrary.PolicyInjection.CallHandlers; using Microsoft.Practices.Unity; using Microsoft.Practices.Unity.InterceptionExtension; namespace Artech.InterceptableUnity { class Program { static void Main(string[] args) { IUnityContainer container = new UnityContainer(); container.RegisterType<ISyncTimeServiceProvision, SyncTimeServiceProvisionService>(); container.RegisterType<ISyncTimeProvider, SyncTimeProvider>(); container.AddNewExtension<Interception>(); container.Configure<Interception>().SetDefaultInterceptorFor(typeof(ISyncTimeServiceProvider), new TransparentProxyInterceptor()); var syncTimeServiceProvision = container.Resolve<ISyncTimeServiceProvision>(); for (int i = 0; i < 5; i++) { Console.WriteLine(syncTimeServiceProvision.GetCurrentTime()); Thread.Sleep(1000); } } } }
通过下面的输出,我们看出输出的时间都是相同的,从而证实了CachingCallHandlerAttribute的有效性,进而正式了UnityContainer和PIAB的集成:
二、通过自定义UnityContainerExtension的方式实现Unity与PIAB的集成
通过Microsoft.Practices.Unity.InterceptionExtension.Interception对Unity和 PIAB两者之间的集成,需要我们借助Interception为每一个需要被劫持(Interception)的类型注册相应的 Interceptor(实现接口 Microsoft.Practices.Unity.InterceptionExtension.IInterceptor),如下面的代码片断所 示。
container.Configure<Interception>().SetDefaultInterceptorFor(typeof(ISyncTimeServiceProvider), new TransparentProxyInterceptor());
但是在每多情况下,我们不可能预先确定需要注册哪些对象,或者这样的类型很多,手工注册的方式将不具有可操作性。比如,在一个N-Layer的应用 中,上层的对象通过UnityContainer创建下层对象,并且通过PIAB的方式将不同的Crosscutting Concern应用于相应的层次,我们不可能对每一个应用了PAIB CallHandler相关的类型进行Interceptor的注册。
为此,我对Interception进行了扩展,实现了Interceptor的动态注册。Unity采用两种不同的 InterceptionStrategy:InstanceInterceptionStrategy和 TypeInterceptionStrategy,它们分别采用基于InstanceInterceptor和TypeInterceptor实现方法 调用劫持。我继承了InstanceInterceptionStrategy和TypeInterceptionStrategy,将 Inteceptor的动态注册定义在PreBuildUp方法中。继承自Interception,在Initialize方法中将两个扩展的 InstanceInterceptionStrategy和TypeInterceptionStrategy—— ExtendedInstanceInterceptionStrategy和ExtendedTypeInterceptionStrategy添加到 UnityContainer的BuildStrategy列表中。在这个扩展的Inteception——ExtendedInterception 中,被用于动态注册的Interceptor定义在ExtendedInterception中,默认为 TransparentProxyInteceptor。下面是ExtendedInterception、 ExtendedInstanceInterceptionStrategy和ExtendedTypeInterceptionStrategy的定 义:
ExtendedInterception:
using Microsoft.Practices.Unity.InterceptionExtension; using Microsoft.Practices.Unity.ObjectBuilder; namespace Artech.InterceptableUnity { public class ExtendedInterception : Interception { public IInterceptor Interceptor { get; internal set; } public ExtendedInterception() { this.Interceptor = new TransparentProxyInterceptor(); } protected override void Initialize() { this.Context.Strategies.Add(new ExtendedInstanceInterceptionStrategy(this), UnityBuildStage.Setup); this.Context.Strategies.Add(new ExtendedTypeInterceptionStrategy(this), UnityBuildStage.PreCreation); this.Context.Container.RegisterInstance<InjectionPolicy>(typeof(AttributeDrivenPolicy).AssemblyQualifiedName, new AttributeDrivenPolicy()); } } }
ExtendedInstanceInterceptionStrategy:
using System; using Microsoft.Practices.ObjectBuilder2; using Microsoft.Practices.Unity; using Microsoft.Practices.Unity.InterceptionExtension; namespace Artech.InterceptableUnity { public class ExtendedInstanceInterceptionStrategy : InstanceInterceptionStrategy { public ExtendedInterception Interception { get; private set; } public ExtendedInstanceInterceptionStrategy(ExtendedInterception interception) { if (null == interception) { throw new ArgumentNullException("interception"); } this.Interception = interception; } private static IInstanceInterceptionPolicy FindInterceptorPolicy(IBuilderContext context) { Type buildKey = BuildKey.GetType(context.BuildKey); Type type = BuildKey.GetType(context.OriginalBuildKey); IInstanceInterceptionPolicy policy = context.Policies.Get<IInstanceInterceptionPolicy>(context.BuildKey, false) ?? context.Policies.Get<IInstanceInterceptionPolicy>(buildKey, false); if (policy != null) { return policy; } policy = context.Policies.Get<IInstanceInterceptionPolicy>(context.OriginalBuildKey, false) ?? context.Policies.Get<IInstanceInterceptionPolicy>(type, false); return policy; } public override void PreBuildUp(IBuilderContext context) { if (BuildKey.GetType(context.BuildKey) == typeof(IUnityContainer)) { return; } IInstanceInterceptionPolicy policy = FindInterceptorPolicy(context); if (null != policy) { if (policy.Interceptor.CanIntercept(BuildKey.GetType(context.BuildKey))) { this.Interception.SetDefaultInterceptorFor(BuildKey.GetType(context.BuildKey), policy.Interceptor); } } else { if (this.Interception.Interceptor.CanIntercept(BuildKey.GetType(context.BuildKey)) && this.Interception.Interceptor is IInstanceInterceptor) { this.Interception.SetDefaultInterceptorFor(BuildKey.GetType(context.BuildKey), (IInstanceInterceptor)this.Interception.Interceptor); } } base.PreBuildUp(context); } } }
ExtendedTypeInterceptionStrategy:
using System; using Microsoft.Practices.ObjectBuilder2; using Microsoft.Practices.Unity.InterceptionExtension; namespace Artech.InterceptableUnity { public class ExtendedTypeInterceptionStrategy : TypeInterceptionStrategy { public ExtendedInterception Interception { get; private set; } public ExtendedTypeInterceptionStrategy(ExtendedInterception interception) { if (null == interception) { throw new ArgumentNullException("interception"); } this.Interception = interception; } private static ITypeInterceptionPolicy GetInterceptionPolicy(IBuilderContext context) { ITypeInterceptionPolicy policy = context.Policies.Get<ITypeInterceptionPolicy>(context.BuildKey, false); if (policy == null) { policy = context.Policies.Get<ITypeInterceptionPolicy>(BuildKey.GetType(context.BuildKey), false); } return policy; } public override void PreBuildUp(IBuilderContext context) { var policy = GetInterceptionPolicy(context); if (null != policy) { if (policy.Interceptor.CanIntercept(BuildKey.GetType(context.BuildKey))) { this.Interception.SetInterceptorFor(BuildKey.GetType(context.BuildKey), policy.Interceptor); } } else { if (this.Interception.Interceptor.CanIntercept(BuildKey.GetType(context.BuildKey)) && this.Interception.Interceptor is ITypeInterceptor) { this.Interception.SetDefaultInterceptorFor(BuildKey.GetType(context.BuildKey), (ITypeInterceptor)this.Interception.Interceptor); } } base.PreBuildUp(context); } } }
那么使用的时候,动态注册Interceptor的操作将不再需要,如下面代码片断所示:
using System; using System.Threading; using Microsoft.Practices.EnterpriseLibrary.PolicyInjection.CallHandlers; using Microsoft.Practices.Unity; using Microsoft.Practices.Unity.InterceptionExtension; namespace Artech.InterceptableUnity { class Program { static void Main(string[] args) { IUnityContainer container = new UnityContainer(); container.RegisterType<ISyncTimeServiceProvision, SyncTimeServiceProvisionService>(); container.RegisterType<ISyncTimeServiceProvider, SyncTimeServiceProvider>(); ExtendedInterception interception = new ExtendedInterception(); interception.Interceptor = new TransparentProxyInterceptor(); container.AddExtension(interception); var syncTimeServiceProvision = container.Resolve<ISyncTimeServiceProvision>(); for (int i = 0; i < 5; i++) { Console.WriteLine(syncTimeServiceProvision.GetCurrentTime()); Thread.Sleep(1000); } } }
三、通过配置的方式应用ExtendedInterception
为了通过配置的方式应用ExtendedInterception,我们需要为之定义相应的配置类型,一个继承自 Microsoft.Practices.Unity.Configuration.UnityContainerExtensionConfigurationElement 得类型。为此,我定义了下面一个ExtendedInterceptionElement类型,配置属性为默认的Inteceptor的类型。
using System; using System.Configuration; using Microsoft.Practices.Unity; using Microsoft.Practices.Unity.Configuration; using Microsoft.Practices.Unity.InterceptionExtension; namespace Artech.InterceptableUnity { public class ExtendedInterceptionElement : UnityContainerExtensionConfigurationElement { [ConfigurationProperty("interceptor", IsRequired = false, DefaultValue = "")] public string Interceptor { get { return (string)this["interceptor"]; } } public override void Configure(IUnityContainer container) { base.Configure(container); ExtendedInterception interception = new ExtendedInterception(); if (!string.IsNullOrEmpty(this.Interceptor)) { var type = System.Type.GetType(this.Interceptor); if (null == type) { throw new ConfigurationErrorsException(string.Format("The {0} is not a valid Interceptor.", this.Interceptor)); } if (!typeof(IInterceptor).IsAssignableFrom(type)) { throw new ConfigurationErrorsException(string.Format("The {0} is not a valid Interceptor.", this.Interceptor)); } interception.Interceptor = (IInterceptor)Activator.CreateInstance(type); } container.AddExtension(interception); } } }
那么对于上面的例子,我么可以将Type Mapping和ExtendedInterception扩展定义在如下一个配置文件中:
<?xml version="1.0" encoding="utf-8" ?> <configuration> <configSections> <section name="unity" type="Microsoft.Practices.Unity.Configuration.UnityConfigurationSection,Microsoft.Practices.Unity.Configuration, Version=1.2.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" /> </configSections> <unity> <typeAliases> <typeAlias alias="ISyncTimeServiceProvision" type="Artech.InterceptableUnity.ISyncTimeServiceProvision,Artech.InterceptableUnity" /> <typeAlias alias="SyncTimeServiceProvisionService" type="Artech.InterceptableUnity.SyncTimeServiceProvisionService,Artech.InterceptableUnity" /> <typeAlias alias="ISyncTimeProvider" type="Artech.InterceptableUnity.ISyncTimeProvider,Artech.InterceptableUnity" /> <typeAlias alias="SyncTimeProvider" type="Artech.InterceptableUnity.SyncTimeProvider,Artech.InterceptableUnity" /> </typeAliases> <containers> <container> <types> <type type="ISyncTimeServiceProvision" mapTo="SyncTimeServiceProvisionService" /> <type type="ISyncTimeProvider" mapTo="SyncTimeProvider" /> </types> <extensionConfig> <add name="extendedInterception" type="Artech.InterceptableUnity.ExtendedInterceptionElement,Artech.InterceptableUnity" interceptor="Microsoft.Practices.Unity.InterceptionExtension.TransparentProxyInterceptor,Microsoft.Practices.Unity.Interception, Version=1.2.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35"/> </extensionConfig> </container> </containers> </unity> </configuration>
那么我们的代码将会变得异常简洁:
using System; using System.Threading; using Microsoft.Practices.EnterpriseLibrary.PolicyInjection.CallHandlers; using Microsoft.Practices.Unity; using Microsoft.Practices.Unity.InterceptionExtension; using Microsoft.Practices.Unity.Configuration; using System.Configuration; namespace Artech.InterceptableUnity { class Program { static void Main(string[] args) { IUnityContainer container = new UnityContainer(); UnityConfigurationSection configuration = (UnityConfigurationSection)ConfigurationManager.GetSection("unity") ; configuration.Containers.Default.Configure(container); var syncTimeServiceProvision = container.Resolve<ISyncTimeServiceProvision>(); for (int i = 0; i < 5; i++) { Console.WriteLine(syncTimeServiceProvision.GetCurrentTime()); Thread.Sleep(1000); } } } }
作者:Artech
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