一、介绍
我们做开发的,尤其是做微软技术栈的,有一个方向是跳不过去的,那就是MVC开发。我相信大家,做ASP.NET MVC 开发有的有很长时间,当然,也有刚进入这个行业的。无论如何,如果有人问你,你知道ASP.NET MVC的生命周期吗?你知道它的来世今生吗?你知道它和 ASP.NET WEBFORM 有什么区别吗?估计,这些问题,有很多人会答不上来,或者说不清楚。今天,我就把我的理解写出来,也是对我自己学习的一次回顾和总结吧。当然,由于本人能力有限,在写的过程中也可能会有一些错误,希望大家多多包涵,当然,更希望大家能不灵赐教,我们共同进步。
在开始之前,我们先来说说,ASP.NET Web Form 和 Asp.net MVC 有什么区别,这里说的区别,当然是本质区别,不是适用语法那个层次的。其实,说起来,ASP.NET WEB FORM 和 ASP.NET MVC 它们两个没有本质区别,使用的都是ASP.NET WEB FORM 的管道处理模型,ASP.NET MVC 也是通过扩展 IHttpModule 和 IHttpHandler 来实现的,都是基于 ASP.NET 的 HttpApplication 的管道处理模型扩展的,在这个层面来说,它们是一样的。当然,大家不要抬杠,我说的本质区别都是在这个方面,不同意的勿喷。
有人会问,ASP.NET MVC 和 ASP.NET WEBAPI 它们会有什么不同吗?好像 WebAPi 能做的,WebMVC都可以完成,第一眼看上去,好像是这样,但是它们有着本质的不同。WebAPI 的处理管道是重新写过的,不是基于 HTTPApplication 管道扩展的。ASP.NET WEB API 类似专人做专事,它的管道处理模型更高效,并且有了 Restfull 的概念。当然,大家如何向了解更细的内容,就需要看源码了。或再说回来,到了 NET CORE 时代,二者又融合管道了。
二、MVC生命周期详述
1、我们既然要说 ASP.NET MVC的生命周期,为了给大家一个整体印象,俗话说,文不如图,我就贴一张图,按着箭头走,相信大家也会不能理解。
2、上图很简单,大家按着箭头走,也能理解的差不多。以下是按着我的理解,划分了4个模块。
(1)、路由模块
RouteBase 是对路由规则的抽象,也就是说,一个 RouteBase 对象,也就代表了一个条 路由规则。在 ASP.NET MVC 中,有一个唯一的子类实现就是 Route ,它同样也是路由规则的代表。我们有了路由规则,一定会把这个规则存放在一个地方,这个地方保存了很多路由规则,这个地方就是 RouteCollection,中文叫“路由集合”,因为这个集合里面包含的就是 RouteBase 对象。
RouteCollection 就是路由集合,用于保存路由规则对象,它的定义形式:
[TypeForwardedFrom("System.Web.Routing, Version=3.5.0.0, Culture=Neutral, PublicKeyToken=31bf3856ad364e35")] public class RouteCollection : Collection<RouteBase> { private class ReadLockDisposable : IDisposable { private ReaderWriterLockSlim _rwLock; public ReadLockDisposable(ReaderWriterLockSlim rwLock) { this._rwLock = rwLock; } void IDisposable.Dispose() { this._rwLock.ExitReadLock(); } } ......
RouteTable 就是路由表,其实它和 RouteCollection 是一样的。
public class RouteTable { private static RouteCollection _instance = new RouteCollection(); public static RouteCollection Routes { get { return RouteTable._instance; } } }
在ASP.NET MVC处理管线中的第一站就是路由模块。当请求到达路由模块后,ASP.NET MVC 框架就会根据 RouteTable 中配置的路由模板来匹配当前请求以获得对应的 Controller 和 Action 信息。具体的匹配过程就是有UrlRoutingModule(System.Web.Routing.UrlRoutingModule)来实现的。如果遇到一个匹配的规则,就会立刻跳出下面的配置。也就是说,配置过程是有顺序的,如果有一个匹配,后面就算有匹配的也不会执行的。
namespace System.Web.Routing { [TypeForwardedFrom("System.Web.Routing, Version=3.5.0.0, Culture=Neutral, PublicKeyToken=31bf3856ad364e35")] public class UrlRoutingModule : IHttpModule { private static readonly object _contextKey = new object(); private static readonly object _requestDataKey = new object(); private RouteCollection _routeCollection; public RouteCollection RouteCollection { get { if (this._routeCollection == null) { this._routeCollection = RouteTable.Routes; } return this._routeCollection; } set { this._routeCollection = value; } } protected virtual void Dispose() { } protected virtual void Init(HttpApplication application) { if (application.Context.Items[UrlRoutingModule._contextKey] != null) { return; } application.Context.Items[UrlRoutingModule._contextKey] = UrlRoutingModule._contextKey; application.PostResolveRequestCache += new EventHandler(this.OnApplicationPostResolveRequestCache); } private void OnApplicationPostResolveRequestCache(object sender, EventArgs e) { HttpApplication httpApplication = (HttpApplication)sender; HttpContextBase context = new HttpContextWrapper(httpApplication.Context); this.PostResolveRequestCache(context); } [Obsolete("This method is obsolete. Override the Init method to use the PostMapRequestHandler event.")] public virtual void PostMapRequestHandler(HttpContextBase context) { } public virtual void PostResolveRequestCache(HttpContextBase context) { RouteData routeData = this.RouteCollection.GetRouteData(context); 第一步匹配路由规则 if (routeData == null) { return; } IRouteHandler routeHandler = routeData.RouteHandler; 第二步:如有匹配,就找到RouteHandler对象,该类型的实例是:MvcRouteHandler。 if (routeHandler == null) { throw new InvalidOperationException(string.Format(CultureInfo.CurrentCulture, SR.GetString("UrlRoutingModule_NoRouteHandler"), new object[0])); } if (routeHandler is StopRoutingHandler) { return; } RequestContext requestContext = new RequestContext(context, routeData); context.Request.RequestContext = requestContext; IHttpHandler httpHandler = routeHandler.GetHttpHandler(requestContext);第三步,根据 RouteHandler 对象,找到最终处理请求的 IHttpHandler 的对象,该类型是 MvcHandler if (httpHandler == null) { throw new InvalidOperationException(string.Format(CultureInfo.CurrentUICulture, SR.GetString("UrlRoutingModule_NoHttpHandler"), new object[] { routeHandler.GetType() })); } if (!(httpHandler is UrlAuthFailureHandler)) { context.RemapHandler(httpHandler);第四步,有找到的 IHttpHandler 处理请求。 return; } if (FormsAuthenticationModule.FormsAuthRequired) { UrlAuthorizationModule.ReportUrlAuthorizationFailure(HttpContext.Current, this); return; } throw new HttpException(401, SR.GetString("Assess_Denied_Description3")); } void IHttpModule.Dispose() { this.Dispose(); } void IHttpModule.Init(HttpApplication application) { this.Init(application); } } }
(2)、Controller 创建模块
经过了路由模块,生成了 RouteData 路由数据,它包含了根据路由规则匹配的 Controller 和 Action。有了路由数据,需要有处理器来处理请求,这个任务就交给了 RouteData 的 RouteHandler 属性,它的类型是 IRouteHandler,它的值就是MvcRouteHandler,MvcRouteHandler 调用 GetHttpHandler 获取处理请求的 IHttpHandler 对象,在 MVC 框架中就是 MvcHandler,详细代码如下:
namespace System.Web.Mvc { /// <summary>Selects the controller that will handle an HTTP request.</summary> public class MvcHandler : IHttpAsyncHandler, IHttpHandler, IRequiresSessionState { private struct ProcessRequestState { internal IAsyncController AsyncController; internal IControllerFactory Factory; internal RequestContext RequestContext; internal void ReleaseController() { this.Factory.ReleaseController(this.AsyncController); } } [CompilerGenerated] [Serializable] private sealed class <>c { public static readonly MvcHandler.<>c <>9 = new MvcHandler.<>c(); public static BeginInvokeDelegate<MvcHandler.ProcessRequestState> <>9__20_0; public static EndInvokeVoidDelegate<MvcHandler.ProcessRequestState> <>9__20_1; public static Func<KeyValuePair<string, object>, bool> <>9__26_0; internal IAsyncResult <BeginProcessRequest>b__20_0(AsyncCallback asyncCallback, object asyncState, MvcHandler.ProcessRequestState innerState) { IAsyncResult result; try { result = innerState.AsyncController.BeginExecute(innerState.RequestContext, asyncCallback, asyncState); } catch { innerState.ReleaseController(); throw; } return result; } internal void <BeginProcessRequest>b__20_1(IAsyncResult asyncResult, MvcHandler.ProcessRequestState innerState) { try { innerState.AsyncController.EndExecute(asyncResult); } finally { innerState.ReleaseController(); } } internal bool <RemoveOptionalRoutingParameters>b__26_0(KeyValuePair<string, object> entry) { return entry.Value == UrlParameter.Optional; } } private static readonly object _processRequestTag = new object(); internal static readonly string MvcVersion = MvcHandler.GetMvcVersionString(); /// <summary>Contains the header name of the ASP.NET MVC version.</summary> public static readonly string MvcVersionHeaderName = "X-AspNetMvc-Version"; private ControllerBuilder _controllerBuilder; internal ControllerBuilder ControllerBuilder { get { if (this._controllerBuilder == null) { this._controllerBuilder = ControllerBuilder.Current; } return this._controllerBuilder; } set { this._controllerBuilder = value; } } /// <summary>Gets or sets a value that indicates whether the MVC response header is disabled.</summary> /// <returns>true if the MVC response header is disabled; otherwise, false.</returns> public static bool DisableMvcResponseHeader { get; set; } /// <summary>Gets a value that indicates whether another request can use the <see cref="T:System.Web.IHttpHandler" /> instance.</summary> /// <returns>true if the <see cref="T:System.Web.IHttpHandler" /> instance is reusable; otherwise, false.</returns> protected virtual bool IsReusable { get { return false; } } /// <summary>Gets the request context.</summary> /// <returns>The request context.</returns> public RequestContext RequestContext { get; private set; } /// <summary>Gets a value that indicates whether another request can use the <see cref="T:System.Web.IHttpHandler" /> instance.</summary> /// <returns>true if the <see cref="T:System.Web.IHttpHandler" /> instance is reusable; otherwise, false.</returns> bool IHttpHandler.IsReusable { get { return this.IsReusable; } } /// <summary>Initializes a new instance of the <see cref="T:System.Web.Mvc.MvcHandler" /> class.</summary> /// <param name="requestContext">The request context.</param> /// <exception cref="T:System.ArgumentNullException">The <paramref name="requestContext" /> parameter is null.</exception> public MvcHandler(RequestContext requestContext) { if (requestContext == null) { throw new ArgumentNullException("requestContext"); } this.RequestContext = requestContext; } /// <summary>Adds the version header by using the specified HTTP context.</summary> /// <param name="httpContext">The HTTP context.</param> protected internal virtual void AddVersionHeader(HttpContextBase httpContext) { if (!MvcHandler.DisableMvcResponseHeader) { httpContext.Response.AppendHeader(MvcHandler.MvcVersionHeaderName, MvcHandler.MvcVersion); } } /// <summary>Called by ASP.NET to begin asynchronous request processing.</summary> /// <returns>The status of the asynchronous call.</returns> /// <param name="httpContext">The HTTP context.</param> /// <param name="callback">The asynchronous callback method.</param> /// <param name="state">The state of the asynchronous object.</param> protected virtual IAsyncResult BeginProcessRequest(HttpContext httpContext, AsyncCallback callback, object state) { HttpContextBase httpContext2 = new HttpContextWrapper(httpContext); return this.BeginProcessRequest(httpContext2, callback, state); } /// <summary>Called by ASP.NET to begin asynchronous request processing using the base HTTP context.</summary> /// <returns>The status of the asynchronous call.</returns> /// <param name="httpContext">The HTTP context.</param> /// <param name="callback">The asynchronous callback method.</param> /// <param name="state">The state of the asynchronous object.</param> protected internal virtual IAsyncResult BeginProcessRequest(HttpContextBase httpContext, AsyncCallback callback, object state) { IController controller; IControllerFactory factory; this.ProcessRequestInit(httpContext, out controller, out factory); IAsyncController asyncController = controller as IAsyncController; if (asyncController != null) { BeginInvokeDelegate<MvcHandler.ProcessRequestState> arg_51_0; if ((arg_51_0 = MvcHandler.<>c.<>9__20_0) == null) { arg_51_0 = (MvcHandler.<>c.<>9__20_0 = new BeginInvokeDelegate<MvcHandler.ProcessRequestState>(MvcHandler.<>c.<>9.<BeginProcessRequest>b__20_0)); } BeginInvokeDelegate<MvcHandler.ProcessRequestState> beginDelegate = arg_51_0; EndInvokeVoidDelegate<MvcHandler.ProcessRequestState> arg_71_0; if ((arg_71_0 = MvcHandler.<>c.<>9__20_1) == null) { arg_71_0 = (MvcHandler.<>c.<>9__20_1 = new EndInvokeVoidDelegate<MvcHandler.ProcessRequestState>(MvcHandler.<>c.<>9.<BeginProcessRequest>b__20_1)); } EndInvokeVoidDelegate<MvcHandler.ProcessRequestState> endDelegate = arg_71_0; MvcHandler.ProcessRequestState invokeState = new MvcHandler.ProcessRequestState { AsyncController = asyncController, Factory = factory, RequestContext = this.RequestContext }; SynchronizationContext synchronizationContext = SynchronizationContextUtil.GetSynchronizationContext(); return AsyncResultWrapper.Begin<MvcHandler.ProcessRequestState>(callback, state, beginDelegate, endDelegate, invokeState, MvcHandler._processRequestTag, -1, synchronizationContext); } Action action = delegate { try { controller.Execute(this.RequestContext); } finally { factory.ReleaseController(controller); } }; return AsyncResultWrapper.BeginSynchronous(callback, state, action, MvcHandler._processRequestTag); } /// <summary>Called by ASP.NET when asynchronous request processing has ended.</summary> /// <param name="asyncResult">The asynchronous result.</param> protected internal virtual void EndProcessRequest(IAsyncResult asyncResult) { AsyncResultWrapper.End(asyncResult, MvcHandler._processRequestTag); } private static string GetMvcVersionString() { return new AssemblyName(typeof(MvcHandler).Assembly.FullName).Version.ToString(2); } /// <summary>Processes the request by using the specified HTTP request context.</summary> /// <param name="httpContext">The HTTP context.</param> protected virtual void ProcessRequest(HttpContext httpContext) { HttpContextBase httpContext2 = new HttpContextWrapper(httpContext); this.ProcessRequest(httpContext2); } /// <summary>Processes the request by using the specified base HTTP request context.</summary> /// <param name="httpContext">The HTTP context.</param> protected internal virtual void ProcessRequest(HttpContextBase httpContext) { IController controller; IControllerFactory controllerFactory; this.ProcessRequestInit(httpContext, out controller, out controllerFactory); try { controller.Execute(this.RequestContext); } finally { controllerFactory.ReleaseController(controller); } } private void ProcessRequestInit(HttpContextBase httpContext, out IController controller, out IControllerFactory factory) { HttpContext current = HttpContext.Current; if (current != null) { bool? flag = ValidationUtility.IsValidationEnabled(current); bool flag2 = true; if (flag.GetValueOrDefault() == flag2 & flag.HasValue) { ValidationUtility.EnableDynamicValidation(current); } } this.AddVersionHeader(httpContext); this.RemoveOptionalRoutingParameters(); string requiredString = this.RequestContext.RouteData.GetRequiredString("controller"); factory = this.ControllerBuilder.GetControllerFactory(); controller = factory.CreateController(this.RequestContext, requiredString); if (controller == null) { throw new InvalidOperationException(string.Format(CultureInfo.CurrentCulture, MvcResources.ControllerBuilder_FactoryReturnedNull, new object[] { factory.GetType(), requiredString })); } } private void RemoveOptionalRoutingParameters() { IDictionary<string, object> arg_2F_0 = this.RequestContext.RouteData.Values; Func<KeyValuePair<string, object>, bool> arg_2F_1; if ((arg_2F_1 = MvcHandler.<>c.<>9__26_0) == null) { arg_2F_1 = (MvcHandler.<>c.<>9__26_0 = new Func<KeyValuePair<string, object>, bool>(MvcHandler.<>c.<>9.<RemoveOptionalRoutingParameters>b__26_0)); } arg_2F_0.RemoveFromDictionary(arg_2F_1); } /// <summary>Enables processing of HTTP Web requests by a custom HTTP handler that implements the <see cref="T:System.Web.IHttpHandler" /> interface.</summary> /// <param name="httpContext">An <see cref="T:System.Web.HttpContext" /> object that provides references to the intrinsic server objects (for example, Request, Response, Session, and Server) that are used to service HTTP requests.</param> void IHttpHandler.ProcessRequest(HttpContext httpContext) { this.ProcessRequest(httpContext); } /// <summary>Called by ASP.NET to begin asynchronous request processing using the base HTTP context.</summary> /// <returns>The status of the asynchronous call.</returns> /// <param name="context">The HTTP context.</param> /// <param name="cb">The asynchronous callback method.</param> /// <param name="extraData">The data.</param> IAsyncResult IHttpAsyncHandler.BeginProcessRequest(HttpContext context, AsyncCallback cb, object extraData) { return this.BeginProcessRequest(context, cb, extraData); } /// <summary>Called by ASP.NET when asynchronous request processing has ended.</summary> /// <param name="result">The asynchronous result.</param> void IHttpAsyncHandler.EndProcessRequest(IAsyncResult result) { this.EndProcessRequest(result); } } } HttpRuntime 调用 IHttpHandler 类型的调用 ProcessRequest() 方法,用于处理请求。 protected internal virtual void ProcessRequest(HttpContextBase httpContext) { IController controller; IControllerFactory controllerFactory; this.ProcessRequestInit(httpContext, out controller, out controllerFactory);创建 IControllerFactory,并创建 IController 对象。 try { controller.Execute(this.RequestContext);执行Controller,背后就是调用相应的 Action 方法。 } finally { controllerFactory.ReleaseController(controller); } }
核心处理请求的方法是ProcessRequestInit(),用于创建 IController 和 IControllerFactory 实例。IControllerFactory 的实际类型是:DefaultControllerFactory,该类型用于创建 IController 类型的实例。
private void ProcessRequestInit(HttpContextBase httpContext, out IController controller, out IControllerFactory factory) { HttpContext current = HttpContext.Current; if (current != null) { bool? flag = ValidationUtility.IsValidationEnabled(current); bool flag2 = true; if (flag.GetValueOrDefault() == flag2 & flag.HasValue) { ValidationUtility.EnableDynamicValidation(current); } } this.AddVersionHeader(httpContext); this.RemoveOptionalRoutingParameters(); string requiredString = this.RequestContext.RouteData.GetRequiredString("controller"); factory = this.ControllerBuilder.GetControllerFactory(); controller = factory.CreateController(this.RequestContext, requiredString); if (controller == null) { throw new InvalidOperationException(string.Format(CultureInfo.CurrentCulture, MvcResources.ControllerBuilder_FactoryReturnedNull, new object[] { factory.GetType(), requiredString })); } }
以上加红的代码就是创建 IController 的实例的逻辑。IController 实例创建完成后,判断是否实现了 IAsyncController 接口,如果是,就异步执行 Controller 方法的调用,否则就同步执行。
protected internal virtual IAsyncResult BeginProcessRequest(HttpContextBase httpContext, AsyncCallback callback, object state) { IController controller; IControllerFactory factory; this.ProcessRequestInit(httpContext, out controller, out factory); IAsyncController asyncController = controller as IAsyncController; 判读是否是需要异步执行 if (asyncController != null)异步执行 { BeginInvokeDelegate<MvcHandler.ProcessRequestState> arg_51_0; if ((arg_51_0 = MvcHandler.<>c.<>9__20_0) == null) { arg_51_0 = (MvcHandler.<>c.<>9__20_0 = new BeginInvokeDelegate<MvcHandler.ProcessRequestState>(MvcHandler.<>c.<>9.<BeginProcessRequest>b__20_0)); } BeginInvokeDelegate<MvcHandler.ProcessRequestState> beginDelegate = arg_51_0; EndInvokeVoidDelegate<MvcHandler.ProcessRequestState> arg_71_0; if ((arg_71_0 = MvcHandler.<>c.<>9__20_1) == null) { arg_71_0 = (MvcHandler.<>c.<>9__20_1 = new EndInvokeVoidDelegate<MvcHandler.ProcessRequestState>(MvcHandler.<>c.<>9.<BeginProcessRequest>b__20_1)); } EndInvokeVoidDelegate<MvcHandler.ProcessRequestState> endDelegate = arg_71_0; MvcHandler.ProcessRequestState invokeState = new MvcHandler.ProcessRequestState { AsyncController = asyncController, Factory = factory, RequestContext = this.RequestContext }; SynchronizationContext synchronizationContext = SynchronizationContextUtil.GetSynchronizationContext(); return AsyncResultWrapper.Begin<MvcHandler.ProcessRequestState>(callback, state, beginDelegate, endDelegate, invokeState, MvcHandler._processRequestTag, -1, synchronizationContext); } Action action = delegate//同步执行。 { try { controller.Execute(this.RequestContext); } finally { factory.ReleaseController(controller); } }; return AsyncResultWrapper.BeginSynchronous(callback, state, action, MvcHandler._processRequestTag); }
(3)、Action 执行模块,通过 ControllerActionInvoker 调用 InvokeAction() 执行其方法。Action 方法的执行也有2个版本,一个是异步版本,一个是同步版本。由于 ActionInvoker 实现了 IAsyncActionInvoker 接口,所以也是以已方式执行。该类型是 AsyncControllerActionInvoker。
A、当Controller对象被创建之后,紧接着就会执行Controler 对象的 Execute(),其实背后就是调用 InvokeAction() 方法:
public virtual bool InvokeAction(ControllerContext controllerContext, string actionName) { if (controllerContext == null) { throw new ArgumentNullException("controllerContext"); } if (string.IsNullOrEmpty(actionName) && !controllerContext.RouteData.HasDirectRouteMatch()) { throw new ArgumentException(MvcResources.Common_NullOrEmpty, "actionName"); } ControllerDescriptor controllerDescriptor = this.GetControllerDescriptor(controllerContext); ActionDescriptor actionDescriptor = this.FindAction(controllerContext, controllerDescriptor, actionName); if (actionDescriptor != null) { FilterInfo filters = this.GetFilters(controllerContext, actionDescriptor); 获取所有过滤器,全局的、控制器的和方法的 try { AuthenticationContext authenticationContext = this.InvokeAuthenticationFilters(controllerContext, filters.AuthenticationFilters, actionDescriptor);认证过滤器的执行。 if (authenticationContext.Result != null) { AuthenticationChallengeContext authenticationChallengeContext = this.InvokeAuthenticationFiltersChallenge(controllerContext, filters.AuthenticationFilters, actionDescriptor, authenticationContext.Result); this.InvokeActionResult(controllerContext, authenticationChallengeContext.Result ?? authenticationContext.Result); } else { AuthorizationContext authorizationContext = this.InvokeAuthorizationFilters(controllerContext, filters.AuthorizationFilters, actionDescriptor);授权过滤器的执行。 if (authorizationContext.Result != null) { AuthenticationChallengeContext authenticationChallengeContext2 = this.InvokeAuthenticationFiltersChallenge(controllerContext, filters.AuthenticationFilters, actionDescriptor, authorizationContext.Result); this.InvokeActionResult(controllerContext, authenticationChallengeContext2.Result ?? authorizationContext.Result); } else { if (controllerContext.Controller.ValidateRequest) { ControllerActionInvoker.ValidateRequest(controllerContext); } IDictionary<string, object> parameterValues = this.GetParameterValues(controllerContext, actionDescriptor); 获取方法执行参数。 ActionExecutedContext actionExecutedContext = this.InvokeActionMethodWithFilters(controllerContext, filters.ActionFilters, actionDescriptor, parameterValues); 执行action,同时执行执行方法前后的 IAcctionFilter AuthenticationChallengeContext authenticationChallengeContext3 = this.InvokeAuthenticationFiltersChallenge(controllerContext, filters.AuthenticationFilters, actionDescriptor, actionExecutedContext.Result); this.InvokeActionResultWithFilters(controllerContext, filters.ResultFilters, authenticationChallengeContext3.Result ?? actionExecutedContext.Result); 执行 ActionResult,同时执行方法前后的 IResultFilter } } } catch (ThreadAbortException) { throw; } catch (Exception exception) { ExceptionContext exceptionContext = this.InvokeExceptionFilters(controllerContext, filters.ExceptionFilters, exception); if (!exceptionContext.ExceptionHandled) { throw; } this.InvokeActionResult(controllerContext, exceptionContext.Result);//异常过滤器的执行。 } return true; } return false; }
B、当选择完合适的Action后,接着就是 ModelBinder(默认是System.Web.Mvc.DefaultModelBinder),它会从http请求的参数中提取数据并实现类型转换,数据校验(例如是否必填,数据格式等)以及是否自动装配到action方法的参数中System.Web.Mvc.DefaultModelBinder
protected virtual IDictionary<string, object> GetParameterValues(ControllerContext controllerContext, ActionDescriptor actionDescriptor) { Dictionary<string, object> dictionary = new Dictionary<string, object>(StringComparer.OrdinalIgnoreCase); ParameterDescriptor[] parameters = actionDescriptor.GetParameters(); for (int i = 0; i < parameters.Length; i++) { ParameterDescriptor parameterDescriptor = parameters[i]; dictionary[parameterDescriptor.ParameterName] = this.GetParameterValue(controllerContext, parameterDescriptor); } return dictionary; } protected virtual object GetParameterValue(ControllerContext controllerContext, ParameterDescriptor parameterDescriptor) { Type parameterType = parameterDescriptor.ParameterType; IModelBinder arg_92_0 = this.GetModelBinder(parameterDescriptor); IValueProvider valueProvider = controllerContext.Controller.ValueProvider; string modelName = parameterDescriptor.BindingInfo.Prefix ?? parameterDescriptor.ParameterName; Predicate<string> propertyFilter = ControllerActionInvoker.GetPropertyFilter(parameterDescriptor); ModelBindingContext bindingContext = new ModelBindingContext { FallbackToEmptyPrefix = parameterDescriptor.BindingInfo.Prefix == null, ModelMetadata = ModelMetadataProviders.Current.GetMetadataForType(null, parameterType), ModelName = modelName, ModelState = controllerContext.Controller.ViewData.ModelState, PropertyFilter = propertyFilter, ValueProvider = valueProvider }; return arg_92_0.BindModel(controllerContext, bindingContext) ?? parameterDescriptor.DefaultValue; }
C、Authentication Filter是mvc5中新增的一个Filter,它会先于authorization filter执行,目的是对访问用户的认证。在MVC5之前,认证和授权都是通过authorization filter来实现的,但现在这2个操作就分开来了,各自管各自喽。
AuthenticationContext authenticationContext = this.InvokeAuthenticationFilters(controllerContext, filters.AuthenticationFilters, actionDescriptor); if (authenticationContext.Result != null) { AuthenticationChallengeContext authenticationChallengeContext = this.InvokeAuthenticationFiltersChallenge(controllerContext, filters.AuthenticationFilters, actionDescriptor, authenticationContext.Result); this.InvokeActionResult(controllerContext, authenticationChallengeContext.Result ?? authenticationContext.Result); }
D、Action filters有2个方法OnActionExecuting和OnActionExecuted分别在action执行前后执行。我们也可以通过实现IActionFilter接口来实现你个性化的过滤机制
protected virtual ActionExecutedContext InvokeActionMethodWithFilters(ControllerContext controllerContext, IList<IActionFilter> filters, ActionDescriptor actionDescriptor, IDictionary<string, object> parameters) { ActionExecutingContext preContext = new ActionExecutingContext(controllerContext, actionDescriptor, parameters); Func<ActionExecutedContext> seed = () => new ActionExecutedContext(controllerContext, actionDescriptor, false, null) { Result = this.InvokeActionMethod(controllerContext, actionDescriptor, parameters) }; return filters.Reverse<IActionFilter>().Aggregate(seed, (Func<ActionExecutedContext> next, IActionFilter filter) => () => ControllerActionInvoker.InvokeActionMethodFilter(filter, preContext, next))(); }
E、接下来就是执行我们平时在Action方法中写的代码了(根据请求相应结果)
protected virtual ActionResult InvokeActionMethod(ControllerContext controllerContext, ActionDescriptor actionDescriptor, IDictionary<string, object> parameters) { object actionReturnValue = actionDescriptor.Execute(controllerContext, parameters); return this.CreateActionResult(controllerContext, actionDescriptor, actionReturnValue); }
(4)、ActionResult 执行模块。
A、在 ActionResult 执行前后,仍然会有一个filter(IResultFilter),同样的,通过实现 IResultFilter 接口你可以定制自己的过滤逻辑。
namespace System.Web.Mvc { /// <summary>Defines the methods that are required for a result filter.</summary> public interface IResultFilter { /// <summary>Called before an action result executes.</summary> /// <param name="filterContext">The filter context.</param> void OnResultExecuting(ResultExecutingContext filterContext); /// <summary>Called after an action result executes.</summary> /// <param name="filterContext">The filter context.</param> void OnResultExecuted(ResultExecutedContext filterContext); } }
B、ActionResult 就是把处理的用户请求结果返回。因此 ViewResult, PartialViewResult, RedirectToRouteResult, RedirectResult, ContentResult, JsonResult, FileResult and EmptyResult就是具体的返回类型。
C、上面的返回类型可以大致分为2类:ViewResult 和非ViewResult。对于需要生成html页面给客户端的划到ViewResult,而其他的例如返回文本,json数据等则划分到非ViewResult,对于非ViewResult直接返回就可以了。
View的初始化和渲染呈现
A、对于 ViewResult 最终是由合适的 View Engine 通过调用 IView 的 Render() 方法来渲染的:
namespace System.Web.Mvc { /// <summary>Defines the methods that are required for a view engine.</summary> public interface IViewEngine { /// <summary>Finds the specified partial view by using the specified controller context.</summary> /// <returns>The partial view.</returns> /// <param name="controllerContext">The controller context.</param> /// <param name="partialViewName">The name of the partial view.</param> /// <param name="useCache">true to specify that the view engine returns the cached view, if a cached view exists; otherwise, false.</param> ViewEngineResult FindPartialView(ControllerContext controllerContext, string partialViewName, bool useCache); /// <summary>Finds the specified view by using the specified controller context.</summary> /// <returns>The page view.</returns> /// <param name="controllerContext">The controller context.</param> /// <param name="viewName">The name of the view.</param> /// <param name="masterName">The name of the master.</param> /// <param name="useCache">true to specify that the view engine returns the cached view, if a cached view exists; otherwise, false.</param> ViewEngineResult FindView(ControllerContext controllerContext, string viewName, string masterName, bool useCache); /// <summary>Releases the specified view by using the specified controller context.</summary> /// <param name="controllerContext">The controller context.</param> /// <param name="view">The view.</param> void ReleaseView(ControllerContext controllerContext, IView view); } }
namespace System.Web.Mvc { /// <summary>Defines the methods that are required for a view.</summary> public interface IView { /// <summary>Renders the specified view context by using the specified the writer object.</summary> /// <param name="viewContext">The view context.</param> /// <param name="writer">The writer object.</param> void Render(ViewContext viewContext, TextWriter writer); } }
B、整个处理过程是由 IViewEngine 来实现的。ASP.NET MVC 默认提供 WebForm(.aspx)和 Razor(.cshtml) 模板引擎,你可以通过实现 IViewEngine 接口来实现自己的 ViewEngine,然后在Application_Start方法中做如下注册:
protected void Application_Start() { //移除所有的View引擎包括Webform和Razor ViewEngines.Engines.Clear(); //注册你自己的View引擎 ViewEngines.Engines.Add(new CustomViewEngine()); }
C、最后,Html Helpers将帮我们生成 input 标签,基于AJAX的 form 等等。
(5)、作为总结,将每个节点主要的代码类贴出来。
这就是整个流程的代码节点,有些是同步执行,有些是异步执行,把握关键点,我这里只是谢了一个大概。
UrlRoutingModule-----RouteCollection.GetRouteData(context)----->IRouteHandler routeHandler = routeData.RouteHandler------》IHttpHandler httpHandler = routeHandler.GetHttpHandler(requestContext)-----》context.RemapHandler(httpHandler)------->MvcHandler------->ProcessRequest()------>ProcessRequestInit()--------》IController------>controller.Execute(this.RequestContext)-------->ControllerActionInvoker------->InvoleAction()--------->InvoleActionMethod()------->InvoleActionReslt()
三、结束
今天就到这里了,东西虽然不多,但是也写了2个多小时。今天就算自己有学习了一边,大家一定要好好的把握这个流程,对于解决程序中的问题,扩展框架都有很大的好处。我们作为程序员的,应该要知道其一,也要知道其二。没事,看看源码,我们对框架和我们自己的代码有更深的了解。当然,这样做也是有代价的,需要更多的时间去支持,我相信我们的付出是值得。不忘初心,继续努力。老天不会辜负努力的人。
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