Controller的创建

　　在ControllerBuilder类中设置ControllerFactory，然后使用ControllerFactory创建Controller。 http请求在进入httphandler映射处理时，通过ControllerBuilder的Current获取ControllerFactory，然后使用默认或者注册的（如果注册地话）ControllerFactory创建controller。默认的工厂是一个DefaultControllerFactory对象,由下面代码可以看出。

internal ControllerBuilder(IResolver<IControllerFactory> serviceResolver){      ControllerBuilder controllerBuilder = this;      IResolver<IControllerFactory> resolver = serviceResolver;      if (resolver == null)        resolver = (IResolver<IControllerFactory>) new SingleServiceResolver<IControllerFactory>((Func<IControllerFactory>) (() => this._factoryThunk()),(IControllerFactory) new DefaultControllerFactory()        {          ControllerBuilder = this        }, "ControllerBuilder.GetControllerFactory");      controllerBuilder._serviceResolver = resolver; }

　　而Controller的产生是通过DefaultControllerFactory的CreateController来实现的，代码如下：

public virtual IController CreateController(RequestContext requestContext, string controllerName){      if (requestContext == null)        throw new ArgumentNullException("requestContext");      if (string.IsNullOrEmpty(controllerName))        throw new ArgumentException(MvcResources.Common_NullOrEmpty, "controllerName");      Type controllerType = this.GetControllerType(requestContext, controllerName);      return this.GetControllerInstance(requestContext, controllerType);}

　　然后查看GetControllerType方法：

PRotected internal virtual Type GetControllerType(RequestContext requestContext, string controllerName){      if (string.IsNullOrEmpty(controllerName))        throw new ArgumentException(MvcResources.Common_NullOrEmpty, "controllerName");      object obj;      if (requestContext != null && requestContext.RouteData.DataTokens.TryGetValue("Namespaces", out obj))      {        IEnumerable<string> enumerable = obj as IEnumerable<string>;        if (enumerable != null && Enumerable.Any<string>(enumerable))        {          HashSet<string> namespaces = new HashSet<string>(enumerable, (IEqualityComparer<string>) StringComparer.OrdinalIgnoreCase);          Type withinNamespaces = this.GetControllerTypeWithinNamespaces(requestContext.RouteData.Route,　　　　　　　　　　　　　　　　　　　　　 controllerName, namespaces);          if (withinNamespaces != (Type) null || false.Equals(requestContext.RouteData.DataTokens["UseNamespaceFallback"]))            return withinNamespaces;        }      }      if (this.ControllerBuilder.DefaultNamespaces.Count > 0)      {        HashSet<string> namespaces = new HashSet<string>((IEnumerable<string>) this.ControllerBuilder.DefaultNamespaces,  　　　　　　(IEqualityComparer<string>) StringComparer.OrdinalIgnoreCase);        Type withinNamespaces = this.GetControllerTypeWithinNamespaces(requestContext.RouteData.Route, controllerName, namespaces);        if (withinNamespaces != (Type) null)          return withinNamespaces;      }      return this.GetControllerTypeWithinNamespaces(requestContext.RouteData.Route, controllerName, (HashSet<string>) null);}

　　可以看到最终都归结到同一个方法GetControllerTypeWithinNamespaces中，代码如下：

private Type GetControllerTypeWithinNamespaces(RouteBase route, string controllerName, HashSet<string> namespaces){      this.ControllerTypeCache.EnsureInitialized(this.BuildManager);      ICollection<Type> controllerTypes = this.ControllerTypeCache.GetControllerTypes(controllerName, namespaces);      switch (controllerTypes.Count)      {        case 0:          return (Type) null;        case 1:          return Enumerable.First<Type>((IEnumerable<Type>) controllerTypes);        default:          throw DefaultControllerFactory.CreateAmbiguousControllerException(route, controllerName, controllerTypes);      } }

　　而方法EnsureInitialized()是通过IBuildManager获取程序中所有实现了IController的类型，然后在这些类型里用路由数据或者ControllerBuilder中的命名空间和controller的名称进行匹配，如果没有匹配，返回null，如果有一个匹配，返回，如果有多个，抛出异常！

　　现在获取到了controllerType的类型，然后返回到工厂的CreateController的最后一步，查看GetControllerInstance方法,代码如下：

protected internal virtual IController GetControllerInstance(RequestContext requestContext, Type controllerType) {      if (controllerType == (Type) null)      {        throw new HttpException(404, string.Format((IFormatProvider) CultureInfo.CurrentCulture, MvcResources.DefaultControllerFactory_NoControllerFound, new object[1]        {          (object) requestContext.HttpContext.Request.Path        }));      }      else      {        if (typeof (IController).IsAssignableFrom(controllerType))          return this.ControllerActivator.Create(requestContext, controllerType);        throw new ArgumentException(string.Format((IFormatProvider) CultureInfo.CurrentCulture, MvcResources.DefaultControllerFactory_TypeDoesNotSubclassControllerBase, new object[1]        {          (object) controllerType        }), "controllerType");      } }

　　可以看到，这个时候又使用到了另外一个对象ControllerActivator，由DefaultControllerFactory的构造函数可以看出

internal DefaultControllerFactory(IControllerActivator controllerActivator, IResolver<IControllerActivator> activatorResolver, IDependencyResolver dependencyResolver) {      if (controllerActivator != null)        this._controllerActivator = controllerActivator;      else        this._activatorResolver = activatorResolver ?? (IResolver<IControllerActivator>) new SingleServiceResolver<IControllerActivator>((Func<IControllerActivator>) (() => (IControllerActivator) null),(IControllerActivator) new DefaultControllerFactory.DefaultControllerActivator(dependencyResolver),　"DefaultControllerFactory constructor"); }

默认使用的是实现了接口IResolver<TService>的SingleServiceResolver<TService>对象默认注册的一个内部对象DefaultControllerActivator，然后调用它的create方法,代码如下：

public IController Create(RequestContext requestContext, Type controllerType) {        try        {          return (IController) (this._resolverThunk().GetService(controllerType) ?? Activator.CreateInstance(controllerType));        }        catch (Exception ex)        {          throw new InvalidOperationException(string.Format((IFormatProvider) CultureInfo.CurrentCulture, MvcResources.DefaultControllerFactory_ErrorCreatingController, new object[1]          {            (object) controllerType          }), ex);        } }

　　而DefaultControllerActivator对象中的属性_resolverThunk是一个Func<IDependencyResolver> _resolverThunk委托对象，我们通过DefaultControllerFactory构造函数中调用的new DefaultControllerFactory.DefaultControllerActivator(dependencyResolver)，可以看到DefaultControllerActivator的构造函数

public DefaultControllerActivator(IDependencyResolver resolver){        if (resolver == null)          this._resolverThunk = (Func<IDependencyResolver>) (() => DependencyResolver.Current);        else          this._resolverThunk = (Func<IDependencyResolver>) (() => resolver);}

　　对它的设置，如果在自己实现的ControllerFactory的构造函数中传递了自己定义的一个IDependencyResolver对象或者DependencyResolver的SetResolver方法设置了一个自定义的IDependencyResolver对象，就会使用它，如果没有，则使用默认的DependencyResolver.Current,可以看到DependencyResolver.Current是一个实现了IDependencyResolver接口对象的引用，从他的构造函数

public DependencyResolver(){      this.InnerSetResolver((IDependencyResolver) new DependencyResolver.DefaultDependencyResolver());}

　　看出它使用的是一个内部私有的对象DefaultDependencyResolver，

private class DefaultDependencyResolver : IDependencyResolver{      public object GetService(Type serviceType)      {        if (!serviceType.IsInterface)        {          if (!serviceType.IsAbstract)          {            try            {              return Activator.CreateInstance(serviceType);            }            catch            {              return (object) null;            }          }