Controller的建立

　　在ControllerBuilder类中设置ControllerFactory，而后使用ControllerFactory建立Controller。 http请求在进入httphandler映射处理时，经过ControllerBuilder的Current获取ControllerFactory，而后使用默认或者注册的（若是注册地话）ControllerFactory建立controller。默认的工厂是一个DefaultControllerFactory对象,由下面代码能够看出。

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的产生是经过DefaultControllerFactory的CreateController来实现的，代码以下：

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);
}

　　而后查看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);
}

　　能够看到最终都归结到同一个方法GetControllerTypeWithinNamespaces中，代码以下：

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()是经过IBuildManager获取程序中全部实现了IController的类型，而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，若是没有匹配，返回null，若是有一个匹配，返回，若是有多个，抛出异常！

　　如今获取到了controllerType的类型，而后返回到工厂的CreateController的最后一步，查看GetControllerInstance方法,代码以下：

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");
      }
 }

　　能够看到，这个时候又使用到了另一个对象ControllerActivator，由DefaultControllerFactory的构造函数能够看出

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，而后调用它的create方法,代码以下：

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，咱们经过DefaultControllerFactory构造函数中调用的new DefaultControllerFactory.DefaultControllerActivator(dependencyResolver)，能够看到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，若是在本身实现的ControllerFactory的构造函数中传递了本身定义的一个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，若是没有，则使用默认的DependencyResolver.Current,能够看到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;
            }
          }
        }
        return (object) null;
      }

      public IEnumerable<object> GetServices(Type serviceType)
      {
        return Enumerable.Empty<object>();
      }
 }

它的GetService方法，经过反射建立了咱们须要的controller对象，由此，controller建立成功！

Area中controller的解析过程：

　　首先咱们知道，在程序刚启动时，咱们会调用AreaRegistration.RegisterAllAreas()方法：

 internal static void RegisterAllAreas(RouteCollection routes, IBuildManager buildManager, object state)
{
      foreach (Type type in TypeCacheUtil.GetFilteredTypesFromAssemblies("MVC-AreaRegistrationTypeCache.xml",  　　　　　　　　　　new Predicate<Type>(AreaRegistration.IsAreaRegistrationType), buildManager))
        ((AreaRegistration) Activator.CreateInstance(type)).CreateContextAndRegister(routes, state);
}

　　它是先查找出程序中全部实现了AreaRegistration的区域对象，而后建立他们的实例，调用实例的CreateContextAndRegister方法，来建立AreaRegistrationContext对象，

internal void CreateContextAndRegister(RouteCollection routes, object state)
{
      AreaRegistrationContext context = new AreaRegistrationContext(this.AreaName, routes, state);
      string @namespace = this.GetType().Namespace;
      if (@namespace != null)
        context.Namespaces.Add(@namespace + ".*");
      this.RegisterArea(context);
}

　　而后调用RegisterArea方法，对路由进行注册，能够看出，这个时候还作了一个额外的事情，就是给上下文的属性Namespaces添加了一个以（区域注册对象所在命名空间+".*")的命名空间，这个最后会用于解析controller对象，经过后续代码能够看出，这个上下文的Namespaces会被使用。

　　而通常的RegisterArea方法就是经过咱们本身建立的区域注册对象来重写实现的，是经过调用AreaRegistrationContext对象的MapRoute()方法来实现路由注册的.

public Route MapRoute(string name, string url, object defaults, object constraints, string[] namespaces)
{
      if (namespaces == null && this.Namespaces != null)
        namespaces = Enumerable.ToArray<string>((IEnumerable<string>) this.Namespaces);
      Route route = RouteCollectionExtensions.MapRoute(this.Routes, name, url, defaults, constraints, namespaces);
      route.DataTokens["area"] = (object) this.AreaName;
      bool flag = namespaces == null || namespaces.Length == 0;
      route.DataTokens["UseNamespaceFallback"] = (object) (bool) (flag ? 1 : 0);
      return route;
}

　　这个方法中咱们看到若是注册路由时没有指定命名空间，则会把上下文的Namespaces属性拿来使用，除了注册路由以外，这个方法还作了一步工做，在路由数据的DataTokens中添加了一个以UseNamespaceFallback为key的数据，它的值是经过判断若是注册路由的命名空间参数和上下文的Namespaces都为空的状况下，为1，不然为0；为1，则在解析controller时须要使用controllerBuilder中的DefaultNamespaces属性的值中的命名空间。这个逻辑咱们能够再DefaultControllerFactory的GetControllerType()方法中能够看到！

　　 并且咱们能够看到路由数据RouteData中表示区域的area的值是存在DataTokens属性中