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在上一篇"ASP.NET MVC请求处理管道生命周期的19个关键环节(7-12) ",体验了7-12关键环节,本篇继续。
⒀当请求到达UrlRoutingModule的时候,UrlRoutingModule取出请求中的Controller、Action等RouteData信息,与路由表中的所有规则进行匹配,若匹配,把请求交给IRouteHandler,即MVCRouteHandler
MVCRouteHandler是用来生成实现IHttpHandler接口的MvcHandler:
namespace System.Web.Routing { public interface IRouteHandler { IHttpHandler GetHttpHandler(RequestContext requestContext); } }
UrlRoutingModule如何把请求交给MVCRouteHandler?
通过分析UrlRoutingModule的源码可以看到:
//通过RouteCollection的静态方法GetRouteData获取到封装路由信息的RouteData实例
RouteData routeData = this.RouteCollection.GetRouteData(context);
//再从RouteData中获取MVCRouteHandler
IRouteHandler routeHandler = routeData.RouteHandler;
为什么可以从RouteData中拿到MVCRouteHadnler呢?
因为当我们在HttpApplication的第一个管道事件,使用MapRoute()方法注册路由的时候,已经通过Route类的构造函数把MVCRouteHandler注入到路由中了。
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, new MvcRouteHandler()) { Defaults = new RouteValueDictionary(defaults), Constraints = new RouteValueDictionary(constraints), DataTokens = new RouteValueDictionary() }; if ((namespaces != null) && (namespaces.Length > 0)) { route.DataTokens["Namespaces"] = namespaces; } routes.Add(name, route); return route; }
⒁MVCRouteHandler把请求交给MvcHandler
还是从UrlRoutingModule的源码可以看到,通过HttpHandler的GetHttpHandler()方法获取到了实现了IHttpHandler接口的MVCHandler:
IHttpHandler httpHandler = routeHandler.GetHttpHandler(requestContext);
context.RemapHandler(httpHandler);
MvcHandler的部分源码为:
public class MvcHandler : IHttpAsyncHandler, IHttpHandler, IRequiresSessionState { protected internal virtual void ProcessRequest(HttpContextBase httpContext) { SecurityUtil.ProcessInApplicationTrust(() => { IController controller; IControllerFactory factory; ProcessRequestInit(httpContext, out controller, out factory);//初始化了ControllerFactory try { controller.Execute(RequestContext); } finally { factory.ReleaseController(controller); } }); } private void ProcessRequestInit(HttpContextBase httpContext, out IController controller, out IControllerFactory factory) { bool? isRequestValidationEnabled = ValidationUtility.IsValidationEnabled(HttpContext.Current); if (isRequestValidationEnabled == true) { ValidationUtility.EnableDynamicValidation(HttpContext.Current); } AddVersionHeader(httpContext); RemoveOptionalRoutingParameters(); string controllerName = RequestContext.RouteData.GetRequiredString("controller"); factory = ControllerBuilder.GetControllerFactory(); controller = factory.CreateController(RequestContext, controllerName); if (controller == null) { throw new InvalidOperationException(String.Format(CultureInfo.CurrentCulture,MvcResources.ControllerBuilder_FactoryReturnedNull,factory.GetType(),controllerName)); } } }
⒂从以上可以看出:首先通过ControllerBuilder的静态方法GetControllerFactory获取到实现IControllerFactory接口的ControllerFactory,然后根据从上下文中的路由数据中拿到controller名称,并据此创建实现IController接口的Controller
Controller派生于ControllerBase, 而ControllerBase实现了IController接口。ControllerBase的部分源码如下:
public abstract class ControllerBase : IController { protected virtual void Execute(RequestContext requestContext) { if (requestContext == null) { throw new ArgumentNullException("requestContext"); } if (requestContext.HttpContext == null) { throw new ArgumentException( MvcResources.ControllerBase_CannotExecuteWithNullHttpContext, "requestContext"); } VerifyExecuteCalledOnce(); Initialize(requestContext); using (ScopeStorage.CreateTransientScope()) { ExecuteCore(); } } protected abstract void ExecuteCore(); ...... }
从中可以看成:
● 每次调用controller,都会执行基类ControllerBase的Execute()方法
● Execute()方法又会调用ExecuteCore()这个抽象方法
● ExecuteCore()这个抽象方法的实现被定义在Controller中
● 在Controller中的ExecuteCore()方法会调用ActionInvoker的InvokeAction()方法
⒃ActionInvoker激发Action方法
ActionInvoker实现了IActionInvoker接口:
public interface IActionInvoker { bool InvokeAction(ControllerContext controllerContext, string actionName); }
MVC默认的ActionInvoker是ControllerActionInvoker。
在Controller类中,提供了类型为IActionInvoker的属性ActionInvoker,当执行ExecuteCore()方法时会让这个ActionInvoker调用InvokeAction()方法激发Action。如下:
public class Controller { ...... private IActionInvoker _actionInvoker; public IActionInvoker ActionInvoker { get { if(_actionInvoker == null) { _actionInvoker = CreateActionInvoker(); } return _actionInvoker; } set { _actionInvoker = value; } } protected virtual IActionInvoker CreateActionInvoker() { return new ControllerActionInvoker(); } public override void ExecuteCore() { ActionInvoker.InvokeAction(...); } ..... }
另外,ActionDescriptor还提供了一个FindAction()方法,用来找到需要被执行的Action。
⒄ActionInvoker在执行InvokeAction()方法返回ActionResult
ActionResult是一个抽象类:
public abstract class ActionResult { public abstract void ExecuteResult(ControllerContext context); }
如果ActionResult是非ViewResult,比如JsonResult, ContentResult,这些内容将直接被输送到Response响应流中,显示给客户端;如果是ViewResult,就会进入下一个渲染视图环节。
⒅ViewEngine找到需要被渲染的视图
默认的有Razor View Engine和Web Form View Engine,实现IViewEngine接口。
IViewEngine接口方法:
● FindPartialView
● FindView
● ReleaseView
如果要创建自定义View Engine,只需要派生于VirtualPathProviderViewEngine这个类。
⒆View被加载成WebViewPage<TModel>类型,并渲染生成Html
调用ViewResult的ExecuteResult()方法,通过IView的Render()方法渲染成Html。
public abstract class ViewResultBase : ActionResult { public override void ExecuteResult(ControllerContext context) { if (context == null) { throw new ArgumentNullException("context"); } if (String.IsNullOrEmpty(ViewName)) { ViewName = context.RouteData.GetRequiredString("action"); } ViewEngineResult result = null; if (View == null) { //通过视图引擎获取到ViewEngineResult ,此时模板页面【aspx】被加载成了WebViewPage<TModel> result = FindView(context); View = result.View; } TextWriter writer = context.HttpContext.Response.Output; ViewContext viewContext = new ViewContext(context, View, ViewData, TempData, writer); View.Render(viewContext, writer); if (result != null) { result.ViewEngine.ReleaseView(context, View); } } }
completed~~
ASP.NET MVC请求处理管道生命周期的19个关键环节(13-19),布布扣,bubuko.com
ASP.NET MVC请求处理管道生命周期的19个关键环节(13-19)
标签:des style class blog code http
原文地址:http://www.cnblogs.com/darrenji/p/3795690.html