004. Asp.Net Routing与MVC 之二： 请求如何激活Controller和Action

 

 

上篇讲到 请求到达 MvcRouteHandler ，并且透过 IRouteHandler.GetHttpHandler 获取到了真正的处理程序 MvcHandler

这次我们看看，MvcHandler是如何依据请求，来激活对应的controller和Action来处理请求的。

 

一、先看看MvcHandler 的核心内容

public class MvcHandler : IHttpAsyncHandler, IHttpHandler, IRequiresSessionState
{
    protected virtual void ProcessRequest(HttpContext httpContext)
    {
        //使用HttpContextWrapper对HttpContext进行封装,封装的目的是为了解耦以获得可测试性.然后从RequestContext.RouteData中提取Controller名称.
        HttpContextBase httpContext2 = new HttpContextWrapper(httpContext);
        this.ProcessRequest(httpContext2);
    }

    protected internal virtual void ProcessRequest(HttpContextBase httpContext)
    {
        IController controller;
        IControllerFactory controllerFactory;
        this.ProcessRequestInit(httpContext, out controller, out controllerFactory);//获取到Controler和ControllerFactory实例，并赋值给局部变量
        try
        {
　　　　　　　　　 //Action的调用，下一篇介绍
                //当前Controler对象的Action的创建与执行（执行包括:加载TempData, 创建及执行Action，处理Action返回的ActionResult ，保存TempData数据）
                controller.Execute(this.RequestContext);

        }
        finally
        {
            //释放当前Controler对象
            controllerFactory.ReleaseController(controller);
        }
    }
}

 

二、Controller的激活

从上述代码中可以看出，对Controller激活的相关的操作是通过MvcHandler类的 ProcessRequestInit 方法来执行，而执行完成后，将获取到Controller和ControllerFactory实例。

this.ProcessRequestInit(httpContext, out controller, out controllerFactory) ，下面就通过这个方法的内部代码来剖析下Controller的激活的机制

private void ProcessRequestInit(HttpContextBase httpContext, out IController controller, out IControllerFactory factory)
{

            // If request validation has already been enabled, make it lazy. This allows attributes like [HttpPost] (which looks
            // at Request.Form) to work correctly without triggering full validation.
            // Tolerate null HttpContext for testing.
            //看不明白
            HttpContext currentContext = HttpContext.Current;
            if (currentContext != null)
            {
                bool? isRequestValidationEnabled = ValidationUtility.IsValidationEnabled(currentContext);
                if (isRequestValidationEnabled == true)
                {
                    ValidationUtility.EnableDynamicValidation(currentContext);
                }
            }
            //为响应添加特定的头标示：MvcVersionHeaderName, MvcVersion
            AddVersionHeader(httpContext);
            //从当前请求的路由集合中，移除可选的路由参数
            RemoveOptionalRoutingParameters();

            // Get the controller type
            //从当前请求的路由集合中,检索名为"controller"参数的值
            string controllerName = RequestContext.RouteData.GetRequiredString("controller");

            // Instantiate the controller and call Execute
            //通过 ControllerBuilder 获取 当前的 controllFactory 控制器工厂
            factory = ControllerBuilder.GetControllerFactory();
            //通过controllFactory 控制器工厂 ，以及前边获取到的 controllerName，构建一个 controller类型实例。
            controller = factory.CreateController(RequestContext, controllerName);
            if (controller == null)
            {
                throw new InvalidOperationException(
                    String.Format(
                        CultureInfo.CurrentCulture,
                        MvcResources.ControllerBuilder_FactoryReturnedNull,
                        factory.GetType(),
                        controllerName));
            }
}

 

由于使用了out关键字，这个方法中的执行过程中所得到的值，即：赋值给ProcessRequest方法中声明的Controller和ControllerFactory

 

 

MVCHander –>  ProcessRequest()

xxxxxController\ControllerFactory

 

IController.Excute();

ControllerBase.Excute().ExcuteCore()

Controller.ExecuteCore()  { . GetActionName  ;  IActionInvoker.InvokeAction() }

IActionInvoker.InvokeAction() {

get methodInfo  //sys

处理参数  // BindModel

methodInfo.invoke();//sys

}

 

1.定义Model

2.Model 里注册事件 ,附加 routerHander

3。routerHander 里 返回真正的  hander

4. hander.ProcessRequest(  HttpCotent content )

{

get Controller type

get Action(Method)  methodinfo

 

var invokeResult = method.Invoke(controllerContext.Controller, parameters.ToArray())
            //as ActionResult;

        controllerContext.RequestContext.HttpContext.Response.Write(invokeResult);

 

 

}

 

一、mvc 下 url 的各种玩法

ip/home/index/3

ip/3

二、

//    parameters.Add(this.ModelBinder.BindModel(controllerContext, parameter.Name, parameter.ParameterType));

 

 

以下是没有搞清楚的内容，如何获取工厂，工厂又如何依据名字，创建一个controller类型实例。

 

显然，上述的代码中有两行重要代码：

1、factory = this.ControllerBuilder.GetControllerFactory();

　 　 this.ControllerBuilder是MvcHandler类的一个属性，属性返回的是MvcHandler类声明的一个 ControllerBuilder类型的字段，属性在返回时会判断当前字段是否为空，如果为空，则调用ControllerBuilder类的静态属性 Current字段，来获取一个ControllerBuilder实例。

接下来再看一下ControllerBuilder类

namespace System.Web.Mvc
{
    public class ControllerBuilder
    {
        //声明静态字段，执行此类的构造函数
        private static ControllerBuilder _instance = new ControllerBuilder();

        private Func<IControllerFactory> _factoryThunk = () => null;
        private HashSet<string> _namespaces = new HashSet<string>(StringComparer.OrdinalIgnoreCase);

        //暂且理解为是封装ControllerFactory的一个类，通过该类的Current属性来获取当前封装的ControllerFactory实例
        private IResolver<IControllerFactory> _serviceResolver;

        public ControllerBuilder()
            : this(null) //: this(null)表示执行带一个参数的构造函数，并且传入的参数为Null
        {
        }

        internal ControllerBuilder(IResolver<IControllerFactory> serviceResolver)
        {
            //如果传入的参数为null，则实例化一个SingleServiceResolver类并赋值给私有字段_serviceResolver。
            _serviceResolver = serviceResolver ?? new SingleServiceResolver<IControllerFactory>(
                                                      () => _factoryThunk(),
                                                      new DefaultControllerFactory { ControllerBuilder = this },
                                                      "ControllerBuilder.GetControllerFactory");
        }

        public static ControllerBuilder Current
        {
            //获取Controller实例
            get { return _instance; }
        }

        public HashSet<string> DefaultNamespaces
        {
            get { return _namespaces; }
        }

        [SuppressMessage("Microsoft.Design", "CA1024:UsePropertiesWhereAppropriate", Justification = "Calling method multiple times might return different objects.")]
        public IControllerFactory GetControllerFactory()
        {
            //获取ControllerFactory实例
            return _serviceResolver.Current;
        }

        public void SetControllerFactory(IControllerFactory controllerFactory)
        {
            if (controllerFactory == null)
            {
                throw new ArgumentNullException("controllerFactory");
            }

            _factoryThunk = () => controllerFactory;
        }

        public void SetControllerFactory(Type controllerFactoryType)
        {
            if (controllerFactoryType == null)
            {
                throw new ArgumentNullException("controllerFactoryType");
            }
            if (!typeof(IControllerFactory).IsAssignableFrom(controllerFactoryType))
            {
                throw new ArgumentException(
                    String.Format(
                        CultureInfo.CurrentCulture,
                        MvcResources.ControllerBuilder_MissingIControllerFactory,
                        controllerFactoryType),
                    "controllerFactoryType");
            }

            _factoryThunk = delegate
            {
                try
                {
                    return (IControllerFactory)Activator.CreateInstance(controllerFactoryType);
                }
                catch (Exception ex)
                {
                    throw new InvalidOperationException(
                        String.Format(
                            CultureInfo.CurrentCulture,
                            MvcResources.ControllerBuilder_ErrorCreatingControllerFactory,
                            controllerFactoryType),
                        ex);
                }
            };
        }
    }
}

 

 

2、controller = factory.CreateController(this.RequestContext, controllername);

　 　此行代码，利用上一句得到一个ControllerFactory实例。将 RequestContext 和Controllername作为参数来调用 ControllerFactory类的CreateController方法，以此创建Controller实例并返回。

 

 

 

 

 

 

至此，我们从请求的 路由数据中，得到 controllerName,又用controllerName，通过 ControllerFactory  获取到了真正的 Controller。

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