MVC Controller

Myth丶恋晨 2021-09-30 12:04 233阅读 0赞

先回顾下之前的MVC执行过程：

一个HttpRequest是如何被ASP.NET和ASP.NET MVC框架执行的：经过IIS和ASP.NET处理后，Core Routing会首先根据URL匹配**物理路径上的文件**，如果不能匹配则由核心路由模块**执行路由**，路由被匹配后，**MvcRouteHandler**会将这个请求“带入”MVC框架，执行Controller和Action。

![2012062916271834.png][]

Controller是如何被创建以及执行的呢？

我们看一下MVCRouteHander的源码：

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namespace System.Web.Mvc
    {
        public class MvcRouteHandler : IRouteHandler
        {
            private IControllerFactory _controllerFactory;
    
            public MvcRouteHandler()
            {
            }
    
            public MvcRouteHandler(IControllerFactory controllerFactory)
            {
                _controllerFactory = controllerFactory;
            }
    
            protected virtual IHttpHandler GetHttpHandler(RequestContext requestContext)
            {
                requestContext.HttpContext.SetSessionStateBehavior(GetSessionStateBehavior(requestContext));
                return new MvcHandler(requestContext);
            }
    
            protected virtual SessionStateBehavior GetSessionStateBehavior(RequestContext requestContext)
            {
                string controllerName = (string)requestContext.RouteData.Values["controller"];
                if (String.IsNullOrWhiteSpace(controllerName))
                {
                    throw new InvalidOperationException(MvcResources.MvcRouteHandler_RouteValuesHasNoController);
                }
    
                IControllerFactory controllerFactory = _controllerFactory ?? ControllerBuilder.Current.GetControllerFactory();
                return controllerFactory.GetControllerSessionBehavior(requestContext, controllerName);
            }
    
            #region IRouteHandler Members
    
            IHttpHandler IRouteHandler.GetHttpHandler(RequestContext requestContext)
            {
                return GetHttpHandler(requestContext);
            }
    
            #endregion
        }
    }

**MvcRouteHandler**的实现仅仅是通过**GetHttpHandler**方法返回一个**MvcHandler**实例。

再来看一下MvcHandler的实现：

![2012071700461382.png][]

核心方法依然是ProcessRequest（异步版BeginProceessRequest）。

protected internal virtual void ProcessRequest(HttpContextBase httpContext)
            {
                IController controller;
                IControllerFactory factory;
                ProcessRequestInit(httpContext, out controller, out factory);
    
                try
                {
                    controller.Execute(RequestContext);
                }
                finally
                {
                    factory.ReleaseController(controller);
                }
            }

ProcessRequestInit方法实现了Controller的创建

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.
                HttpContext currentContext = HttpContext.Current;
                if (currentContext != null)
                {
                    bool? isRequestValidationEnabled = ValidationUtility.IsValidationEnabled(currentContext);
                    if (isRequestValidationEnabled == true)
                    {
                        ValidationUtility.EnableDynamicValidation(currentContext);
                    }
                }
    
                AddVersionHeader(httpContext);
                RemoveOptionalRoutingParameters();
    
                // Get the controller type
                string controllerName = RequestContext.RouteData.GetRequiredString("controller");
    
                // Instantiate the controller and call Execute
                factory = ControllerBuilder.GetControllerFactory();
                controller = factory.CreateController(RequestContext, controllerName);
                if (controller == null)
                {
                    throw new InvalidOperationException(
                        String.Format(
                            CultureInfo.CurrentCulture,
                            MvcResources.ControllerBuilder_FactoryReturnedNull,
                            factory.GetType(),
                            controllerName));
                }
            }

**MvcHandler**从RouteData中获得controller名字负责创建一个**ControllerBuilder**的实例，并通过ControllerBuilder的**GetControllerFactory**返回一个**IControllerFactory**的实例，这个实例就是**DefaultControllerFactory**，它的 **CreateController**方法负责创建需要的Controller实例

// Get the controller type
    string controllerName = RequestContext.RouteData.GetRequiredString("controller");
    // Instantiate the controller and call Execute
    factory = ControllerBuilder.GetControllerFactory();
    controller = factory.CreateController(RequestContext, controllerName);

Controller的执行：

Controller继承自ControllerBase，而Controller又继承自IController，而IController的定义非常简单：

namespace System.Web.Mvc
    {
        public interface IController
        {
            void Execute(RequestContext requestContext);
        }
    }

只有一个Execute（）接口。从接口定义可以看出，当Controller被“调用”的时候，应该负责完成Execute方法，参数**RequestContext**封装了**HttpContext。**

打开**Controller**源文件并没有发现Execute（）方法的实现，那么它应该在**ControllerBase**中，查看**ControllerBase**发现，在，Execute在内部调用ExecuteCore，ExecuteCore作为一个抽象方法，延迟到Controller中实现。ControllerBase只提供了诸如TempData、ViewData等，Controller的ExecuteCore方法真正invoke了action机制，是action的入口。下面的代码是ExecuteCore的实现：

protected override void ExecuteCore()
            {
                // If code in this method needs to be updated, please also check the BeginExecuteCore() and
                // EndExecuteCore() methods of AsyncController to see if that code also must be updated.
    
                PossiblyLoadTempData();
                try
                {
                    string actionName = RouteData.GetRequiredString("action");
                    if (!ActionInvoker.InvokeAction(ControllerContext, actionName))
                    {
                        HandleUnknownAction(actionName);
                    }
                }
                finally
                {
                    PossiblySaveTempData();
                }
            }

可以看到RouteData在这里又提供了action参数，可以想象InvokeAction方法依靠这个action的名字调用action，并实现诸多验证机制

** **

转载于:https://www.cnblogs.com/jyan/archive/2012/07/17/2594508.html

[2012062916271834.png]: /images/20210724/2e5a3f82750c416b903241875c43d0ed.png
[ContractedBlock.gif]: https://images.cnblogs.com/OutliningIndicators/ContractedBlock.gif
[ExpandedBlockStart.gif]: /images/20210724/0beb8b7aa42a44438135a13230d621df.png
[2012071700461382.png]: /images/20210724/b8276d7efc074edfb9b4f1f65ecfeda2.png