MVC 请求处理流程（一）
路由系统先获取路由数据,在实现了IHttpModule接口的UrlRoutingModule对象中通过注册HttpApplication的PostResolveRequestCache来解析路由数据并对请求进行映射；
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);
}
public virtual void PostResolveRequestCache(HttpContextBase context)
{
RouteData routeData = this.RouteCollection.GetRouteData(context);
if (routeData == null)
return;
IRouteHandler routeHandler = routeData.RouteHandler;
if (routeHandler == null)
throw new InvalidOperationException(string.Format((IFormatProvider) CultureInfo.CurrentCulture, System.Web.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);//获取的为MvcHandler
if (httpHandler == null)
throw new InvalidOperationException(string.Format((IFormatProvider) CultureInfo.CurrentUICulture, System.Web.SR.GetString("UrlRoutingModule_NoHttpHandler"), new object[1]
{
(object) routeHandler.GetType()
}));
else if (httpHandler is UrlAuthFailureHandler)
{
if (!FormsAuthenticationModule.FormsAuthRequired)
throw new HttpException(401, System.Web.SR.GetString("Assess_Denied_Description3"));
UrlAuthorizationModule.ReportUrlAuthorizationFailure(HttpContext.Current, (object) this);
}
else
context.RemapHandler(httpHandler);
}
路由数据有个 IRouteHandler RouteHandler属性，注册路由时这个属性默认为MvcRouteHandler
public static Route MapRoute(this RouteCollection routes, string name, string url, object defaults, object constraints, string[] namespaces)
{
if (routes == null)
throw new ArgumentNullException("routes");
if (url == null)
throw new ArgumentNullException("url");
Route route = new Route(url, (IRouteHandler) new MvcRouteHandler())
{
Defaults = RouteCollectionExtensions.CreateRouteValueDictionary(defaults),
Constraints = RouteCollectionExtensions.CreateRouteValueDictionary(constraints),
DataTokens = new RouteValueDictionary()
};
if (namespaces != null && namespaces.Length > 0)
route.DataTokens["Namespaces"] = (object) namespaces;
routes.Add(name, (RouteBase) route);
return route;
}
RouteHandler有个GetHttpHandler方法来获取对当前请求进行映射的HttpHandler(会话状态也是在这个阶段设置的，通过controllerFactory.GetControllerSessionBehavior()方法)
public MvcRouteHandler(IControllerFactory controllerFactory)
{
this._controllerFactory = controllerFactory;
}
protected virtual SessionStateBehavior GetSessionStateBehavior(RequestContext requestContext)
{
string controllerName = (string) requestContext.RouteData.Values["controller"];
if (string.IsNullOrWhiteSpace(controllerName))
throw new InvalidOperationException(MvcResources.MvcRouteHandler_RouteValuesHasNoController);
else
return (this._controllerFactory ?? ControllerBuilder.Current.GetControllerFactory()).GetControllerSessionBehavior(requestContext, controllerName);
}
protected virtual IHttpHandler GetHttpHandler(RequestContext requestContext)
{
requestContext.HttpContext.SetSessionStateBehavior(this.GetSessionStateBehavior(requestContext));
return (IHttpHandler) new MvcHandler(requestContext);
}
返回的是一个实现了IHttpHandler的MvcHandler对象， 在MvcHandler的请求处理方法ProcessRequest中调用了ProcessRequestInit方法，代码如下：
protected internal virtual void ProcessRequest(HttpContextBase httpContext)
{
IController controller;
IControllerFactory factory;
this.ProcessRequestInit(httpContext, out controller, out factory);//获取到当前的controller对象
try
{
controller.Execute(this.RequestContext);//进行进一步的方法调用
}
finally
{
factory.ReleaseController(controller);//完成后释放
}
}
private void ProcessRequestInit(HttpContextBase httpContext, out IController controller, out IControllerFactory factory)
{
HttpContext current = HttpContext.Current;
if (current != null)
{
bool? nullable = ValidationUtility.IsValidationEnabled(current);
if ((!nullable.GetValueOrDefault() ? 0 : (nullable.HasValue ? 1 : 0)) != 0)
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)
return;
throw new InvalidOperationException(string.Format((IFormatProvider) CultureInfo.CurrentCulture, MvcResources.ControllerBuilder_FactoryReturnedNull, new object[2]
{
(object) factory.GetType(),
(object) requiredString
}));
}
以上方法中通过工厂ControllerFactoryController创建Controller的方法详见：[controller的创建"]。controller的Execute方法是在其基类ControllerBase中 实现的
protected virtual void Execute(RequestContext requestContext)
{
if (requestContext == null)
throw new ArgumentNullException("requestContext");
if (requestContext.HttpContext == null)
throw new ArgumentException(MvcResources.ControllerBase_CannotExecuteWithNullHttpContext, "requestContext");
this.VerifyExecuteCalledOnce();
this.Initialize(requestContext);
using (ScopeStorage.CreateTransientScope())
this.ExecuteCore();
}
在其子类controller中重写了方法ExecuteCore
protected override void ExecuteCore()
{
this.PossiblyLoadTempData();
try
{
//获取动作方法名称
string requiredString = this.RouteData.GetRequiredString("action");
if (this.ActionInvoker.InvokeAction(this.ControllerContext, requiredString))
return;
this.HandleUnknownAction(requiredString);
}
finally
{
this.PossiblySaveTempData();
}
}
在这里使用到了ActionInvoker属性，它对应的是实现了IActionInvoker接口的一个对象！默认为获取在this.CreateActionInvoker()方法中，为AsyncControllerActionInvoker对象（这个是最忙的对象）！