通过fsharp 使用Enterprise Library Unity 3 - 三种拦截模式的探索

这篇就三种拦截模式进行一下探索。
                                      

特性总结

	类型	特点	其它
InterfaceInterceptor	Innstance	仅单接口	类内部函数互相引用无法引起拦截行为
TransparentProxyInterceptor	Instance	多接口(接口之间能够切换)  MarshalByRef 执行缓慢 接口类型（virtual, non-virtual, or interface）	类内部函数互相引用能够引起拦截行为
VirtualMethodInterceptor	Type	多接口                                  不能用在已有对象上，接口函数必须为virtual	类内部函数互相引用也能引起拦截行为

回顾一下类的声明。两个接口，一个实现。

fsharp实现接口函数的方法与csharp并不全然一致，会造成一些实现上的困扰，这在后面会提到。

type ITenantStore = 
    abstract member Msg : unit->unit


type TenantStore() as x= 
    //do printfn "new TenantStore %A" (x.GetHashCode())
    interface ITenantStore with
        member this.Msg() = printfn "Hello, it‘s TenantStore"
    interface IDisposable with
        member this.Dispose() = printfn "TenantStore hase been cleaned"

以下进行一些測试。

let showregistrations (container:UnityContainer) = 
    container.Registrations |> Seq.iter (fun i -> printfn "Regist Type:%A" i.RegisteredType)


using(new UnityContainer())(fun ctner->
    ctner.AddNewExtension<Interception>() |> ignore
    ctner.RegisterType<ITenantStore, TenantStore>(new Interceptor<TransparentProxyInterceptor>(),//兴许对此注入策略进行切换
                                                  new InterceptionBehavior<LogingInterceptionBehavior>()) |> ignore
    showregistrations ctner
    let t = ctner.Resolve<ITenantStore>()
    t.Msg())

showregistrations 显示已注冊的类型。用来展示注冊内部的信息。另外，在交互式代码中使用using相较于use更为的合适，FSI声明的对象的生命周期是全局的，在做试验的时候无法控制container。重复清环境不太方便。

TransparentProxyInterceptor的结果

Regist Type:Microsoft.Practices.Unity.IUnityContainer
Regist Type:Microsoft.Practices.Unity.InterceptionExtension.InjectionPolicy
Regist Type:FSI_0002+ITenantStore
From the logging interceptor: "Invoke method System.Type GetType():System.Object at 16:20:45"
From the logging interceptor: "Method System.Type GetType():System.Object returned FSI_0002+TenantStore at 16:20:45"
From the logging interceptor: "Invoke method Void Msg():FSI_0002+ITenantStore at 16:20:45"
Hello, it‘s TenantStore
From the logging interceptor: "Method Void Msg():FSI_0002+ITenantStore returned  at 16:20:45"
val it : unit = ()

InterfaceInterceptor的结果

Regist Type:Microsoft.Practices.Unity.IUnityContainer
Regist Type:Microsoft.Practices.Unity.InterceptionExtension.InjectionPolicy
Regist Type:FSI_0002+ITenantStore
From the logging interceptor: "Invoke method Void Msg():FSI_0002+ITenantStore at 16:22:54"
Hello, it‘s TenantStore
From the logging interceptor: "Method Void Msg():FSI_0002+ITenantStore returned  at 16:22:54"
val it : unit = ()

尽管对象有两个接口，IDiposable接口和ITenantStore接口。拦截仍然成功了，所以支持多对象指的是接口之间的切换，并不是不支持实现多对象的类。

VirtualMethodInterceptor的结果

Regist Type:Microsoft.Practices.Unity.IUnityContainer
Regist Type:Microsoft.Practices.Unity.InterceptionExtension.InjectionPolicy
Regist Type:FSI_0002+ITenantStore
Hello, it‘s TenantStore
val it : unit = ()

拦截失败。 研究后发觉是由于Fsharp中并不直接支持Virtual方法，Fsharp实现接口成员，默觉得显示（explicit）实现，想要申明Virtual方法须要一些技巧。
可參考http://cs.hubfs.net/topic/None/73936


再定义一个測试类来试试VirtualMethodInterceptor。

type testClass() = 
    abstract member Test : unit -> unit
    default x.Test() = 
        printfn "hello "

using(new UnityContainer())(fun ctner->
    ctner.AddNewExtension<Interception>() |> ignore
    ctner.RegisterType<testClass>(new Interceptor<VirtualMethodInterceptor>(),
                                  new InterceptionBehavior<LogingInterceptionBehavior>()) |> ignore
    showregistrations ctner
    let t = ctner.Resolve<testClass>()
    t.Test()
    )

结果

Regist Type:Microsoft.Practices.Unity.IUnityContainer
Regist Type:Microsoft.Practices.Unity.InterceptionExtension.InjectionPolicy
Regist Type:FSI_0002+testClass
From the logging interceptor: "Invoke method Void Test():FSI_0002+testClass at 9:30:27"
hello 
From the logging interceptor: "Method Void Test():FSI_0002+testClass returned  at 9:30:27"
val it : unit = ()

拦截成功。

以下稍加改写原来的类定义。使接口都以virtural的形式暴露出来

type TenantStore() as x= 
    //do printfn "new TenantStore %A" (x.GetHashCode())
    abstract Msg : unit -> unit
    default x.Msg() = 
        printfn "Hello, it‘s TenantStore"
    abstract Dispose : unit -> unit
    default x.Dispose() = 
        printfn "TenantStore hase been cleaned"
    interface ITenantStore with
        member x.Msg() = x.Msg()
    interface IDisposable with
        member x.Dispose() = x.Dispose()

有些繁琐，接口实现的代码能够复用，不幸中的万幸。

以下的样例中我同一时候測试一下多接口之间转换的情况，看看VirtualMethodInterceptor是否也支持多接口。文档上没有明白表明。

測试代码

using(new UnityContainer())(fun ctner->
    ctner.AddNewExtension<Interception>() |> ignore
    ctner.RegisterType<ITenantStore, TenantStore>(new Interceptor<VirtualMethodInterceptor>(),
                                                  new InterceptionBehavior<LogingInterceptionBehavior>()) |> ignore
    ctner.RegisterType<testClass>(new Interceptor<VirtualMethodInterceptor>(),
                                  new InterceptionBehavior<LogingInterceptionBehavior>()) |> ignore
    showregistrations ctner
    let t = ctner.Resolve<ITenantStore>()
    t.Msg()
    let o = (box t) :?
> IDisposable
    o.Dispose()
    )

TransparentProxyInterceptor
成功 结果

Regist Type:Microsoft.Practices.Unity.IUnityContainer
Regist Type:Microsoft.Practices.Unity.InterceptionExtension.InjectionPolicy
Regist Type:FSI_0002+ITenantStore
From the logging interceptor: "Invoke method System.Type GetType():System.Object at 9:38:47"
From the logging interceptor: "Method System.Type GetType():System.Object returned FSI_0010+TenantStore at 9:38:47"
From the logging interceptor: "Invoke method Void Msg():FSI_0002+ITenantStore at 9:38:47"
Hello, it‘s TenantStore
From the logging interceptor: "Method Void Msg():FSI_0002+ITenantStore returned  at 9:38:47"
From the logging interceptor: "Invoke method System.Type GetType():System.Object at 9:38:47"
From the logging interceptor: "Method System.Type GetType():System.Object returned FSI_0010+TenantStore at 9:38:47"
From the logging interceptor: "Invoke method Void Dispose():System.IDisposable at 9:38:47"
TenantStore hase been cleaned
From the logging interceptor: "Method Void Dispose():System.IDisposable returned  at 9:38:47"
val it : unit = ()

InterfaceInterceptor
失败 结果：

Regist Type:Microsoft.Practices.Unity.IUnityContainer
Regist Type:Microsoft.Practices.Unity.InterceptionExtension.InjectionPolicy
Regist Type:FSI_0002+ITenantStore
From the logging interceptor: "Invoke method Void Msg():FSI_0002+ITenantStore at 9:39:44"
Hello, it‘s TenantStore
From the logging interceptor: "Method Void Msg():FSI_0002+ITenantStore returned  at 9:39:44"
System.InvalidCastException: 无法将类型为“DynamicModule.ns.Wrapped_ITenantStore_67632c824c8e42bbad5925d203ac819b”的对象强制转换为类型“System.IDisposable”。
   在 FSI_0015.it@149-7.Invoke(UnityContainer ctner) 位置 E:\WorkHell\fsharp-practise\EnterpriseLibraryUnity\Program.fs:行号 157
   在 Microsoft.FSharp.Core.Operators.Using[T,TResult](T resource, FSharpFunc`2 action)
   在 <StartupCode$FSI_0015>.$FSI_0015.main@()
已因出错而停止

VirtualMethodInterceptor
成功 结果

Regist Type:Microsoft.Practices.Unity.IUnityContainer
Regist Type:Microsoft.Practices.Unity.InterceptionExtension.InjectionPolicy
Regist Type:FSI_0002+ITenantStore
Regist Type:FSI_0002+testClass
From the logging interceptor: "Invoke method Void Msg():FSI_0017+TenantStore at 9:42:01"
Hello, it‘s TenantStore
From the logging interceptor: "Method Void Msg():FSI_0017+TenantStore returned  at 9:42:01"
From the logging interceptor: "Invoke method Void Dispose():FSI_0017+TenantStore at 9:42:01"
TenantStore hase been cleaned
From the logging interceptor: "Method Void Dispose():FSI_0017+TenantStore returned  at 9:42:01"
val it : unit = ()

通过结果能够看到TransparentProxyInterceptor在构建的过程中多了一些步骤。翻了一下帮助文档。说这个代理是使用 TransparentProxy/RealProxy infrastructure生成的。因而速度最慢。

而另两个则是通过动态代码生成的（这是什么？反射？）。


这里能够有个小的结论了，InterfaceInterceptor最小巧有用，其它两个或多或少在使用上都要留意一下各自的特性。
再看看可替换性。

(box t) :?> TenantStore

结果
TransparentInterceptor 失败
VirtualMethodInterceptor 成功
InterfaceInterceptor 失败   和料想的一致

以上