Agenda
前言
前一篇介紹路由封裝了Http請求路徑資訊可以讓我們找到相對應的Action
和Controller
並呼叫執行外,也可透過MapPageRoute
來將請求教給.aspx
實體檔案來處理請求.
Route
甚至可以讓我們自己客製化處理HttpHandler
在Route中建立處理客製化HttpHandler可謂很有彈性
本篇介紹Route
物件建立MvcRouteHandler
物件且如何取到IHttpHandler
.
我有做一個可以針對於Asp.net MVC Debugger的專案,只要下中斷點就可輕易進入Asp.net MVC原始碼.
MVC取得使用HttpHandler (IHttpHandler)
之前說到我們透過MapRoute
擴展方法加入一個Route
物件給RouteCollection
全域路由集合.
在Route
使用的IRouteHandler
介面是由MvcRouteHandler
來實現
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| Route route = new Route(url, new MvcRouteHandler()) { Defaults = CreateRouteValueDictionaryUncached(defaults), Constraints = CreateRouteValueDictionaryUncached(constraints), DataTokens = new RouteValueDictionary() };
|
IRouteHandler
最重要的是IHttpHandler IRouteHandler.GetHttpHandler(RequestContext requestContext)
會取得一個IHttpHandler
物件.
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| 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 }
|
上面程式碼可以看到Mvc使用IHttpHandler
是MvcHandler
MVC呼叫的HttpHandler (MvcHandler)
MvcHandler
類別中主要核心的程式碼做了幾件事情.
- 使用一個
Adapter
對於HttpContext
物件把他轉成可以繼承於HttpContextBase
的HttpContextWrapper
類別.
- 透過
ProcessRequestInit
取得執行controller
物件並且呼叫執行方法.
- 最後透過
ReleaseController
釋放之前使用過資源
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| protected virtual void ProcessRequest(HttpContext httpContext) { HttpContextBase httpContextBase = new HttpContextWrapper(httpContext); ProcessRequest(httpContextBase); }
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); } }
|
小結
今天我們知道MVC使用HttpHandler
是MvcHandler
透過並MvcRouteHandler
物件來返回.
下圖簡單展現MVC使用的HttpModule
和HttpHandler
關係
- 在
UrlRoutingMoudule
註冊事件.
- 取得符合Http請求
Route
物件
- 呼叫
MvcRouteHandler
取得MvcHandler
物件
- 執行
MvcHandler
的ProcessReqeust
方法
下面會陸續介紹MVC是如何取得Controller
物件
__此文作者__:Daniel Shih(石頭)
__此文地址__: https://isdaniel.github.io/Ithelp-day10/
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