文章引導
引言
前面我們講了IgnoreRoute鏈接
現在我們講講核心的MapRoute，還是提前准備Reflection工具，若是沒准備，可以看“”MVC路由深入詳解1---IgnoreRoute”中的System.Web.dll源碼
一.RouteCollection
我們來看看RouteCollection.MapRoute，截圖如下：
相信大家看到了RouteCollectionExtensions是一個靜態類，是對RouteCollection的擴展（關於擴展方法的大家可以百度，此處不做詳細描述）。好家伙，我們看看這個擴展方法走向何方（這個時候就是Reflection發揮作用的時候了）。
引用“”MVC路由深入詳解1---IgnoreRoute”中的內容，看看MapRoute的參數傳入的是什么：
name: "Default"
url: "{controller}/{action}/{id}"
defaults: new { controller = "Home", action = "Index", id = UrlParameter.Optional } --->這是個匿名類型
我們看看擴展方法去了哪里：
public static Route MapRoute(this RouteCollection routes, string name, string url, object defaults) => routes.MapRoute(name, url, defaults, null);
我們接着往下走
public static Route MapRoute(this RouteCollection routes, string name, string url, object defaults, object constraints) =>routes.MapRoute(name, url, defaults, constraints, null);
接着
public Route MapRoute(string name,string url,object defaults,object constraints=null,string[] param=null) { if(url==null) { throw new ArgumentNullException("url"); } Route route = new Route(url, new MvcRouteHandler()) { Defaults=CreateRouteValueDictionaryUncached(defaults), Constraints=CreateRouteValueDictionaryUncached(constraints), DataTokens=new System.Web.Routing.RouteValueDictionary() }; ConstraintValidation.Validate(route); if ((param != null) && (param.Length > 0)) { route.DataTokens["Namespaces"] = param; } Add(name, route); return route; }
上面新建了一個Route,Route就是一條具體的路由 ，new Route(url, new MvcRouteHandler())傳入規則url和new MvcRouteHandler()。
二.CreateRouteValueDictionaryUncached
private static System.Web.Routing.RouteValueDictionary CreateRouteValueDictionaryUncached(object values)
{
IDictionary<string, object> dictionary = values as IDictionary<string, object>;
if (dictionary != null)
{
return new System.Web.Routing.RouteValueDictionary(dictionary);
}
return System.Web.WebPages.TypeHelper.ObjectToDictionaryUncached(values);
}
三.MvcRouteHandler
我們繼續拆解MvcRouteHandler
public class MvcRouteHandler: System.Web.Routing.IRouteHandler
{
System.Web.Mvc.IControllerFactory _controllerFactory;
public MvcRouteHandler() { } public MvcRouteHandler(System.Web.Mvc.IControllerFactory controllFactory) { _controllerFactory = controllFactory; } protected virtual IHttpHandler GetHttpHandler(System.Web.Routing.RequestContext requestContext) { //SetSessionStateBehavior:在派生類重寫時，設置支持HTTP請求所必須的會話狀態行為的類型 requestContext.HttpContext.SetSessionStateBehavior(GetSessionStateBehavior(requestContext)); return new MvcHandler(requestContext); } IHttpHandler System.Web.Routing.IRouteHandler.GetHttpHandler(System.Web.Routing.RequestContext requestContext) { return GetHttpHandler(requestContext); } protected virtual System.Web.SessionState.SessionStateBehavior GetSessionStateBehavior(System.Web.Routing.RequestContext requestContext) { string str = (string)requestContext.RouteData.Values["controller"]; if (string.IsNullOrEmpty(str)) { throw new InvalidOperationException(System.Web.Mvc.Properties.MvcResources.MvcRouteHandler_RouteValuesHasNoController); } IControllerFactory factory = _controllerFactory ?? ControllerBuilder.Current.GetControllerFactory(); return factory.GetControllerSessionBehavior(requestContext, str); } }
四.RouteValueDictionary
RouteValueDictionary是對Dictionary<string,object>進行包裝，下面是RouteValueDictionary拆解
public RouteValueDictionary(object values) { this._dictionary = new Dictionary<string, object>(StringComparer.OrdinalIgnoreCase); this.AddValues(values); } private void AddValues(object values) { if (values != null) { foreach (PropertyDescriptor descriptor in TypeDescriptor.GetProperties(values)) { object obj2 = descriptor.GetValue(values); this.Add(descriptor.Name, obj2); } } }
我們來看看效果
五.Add(name,route)
我們來看看這個Add方法：
public void Add(string name, RouteBase item) { if (item == null) { throw new ArgumentNullException("item"); } if (!string.IsNullOrEmpty(name) && this._namedMap.ContainsKey(name)) { object[] args = new object[] { name }; //throw new ArgumentException(string.Format(CultureInfo.CurrentUICulture, System.Web.SR.GetString("RouteCollection_DuplicateName"), args), "name"); } base.Add(item); if (!string.IsNullOrEmpty(name)) { this._namedMap[name] = item; } }
里面做了重復路由名稱驗證，Add方法的第二個參數是RouteBase,我們看看MapRoute方法里傳入給Add方法的參數是Route。Route是繼承於RouteBase，RouteBase是一個抽象類，這個類是為繼承類服務的，里面定義了GetRouteData和GetVirtualPath兩個抽象方法。
GetRouteData：解析請求url，提取數據，如：/home/index 得到：controller/home,action/index提取得到的數據會包裝成RouteData
GetVirtualPath:生成URL
六.RouteBase Route
public abstract class RouteBase { // Methods protected RouteBase(); public abstract RouteData GetRouteData(HttpContextBase httpContext); public abstract VirtualPathData GetVirtualPath(RequestContext requestContext, RouteValueDictionary values); }
public class Route : RouteBase { // Fields private ParsedRoute _parsedRoute; private string _url; private const string HttpMethodParameterName = "httpMethod"; // Methods public Route(string url, IRouteHandler routeHandler); public Route(string url, RouteValueDictionary defaults, IRouteHandler routeHandler); public Route(string url, RouteValueDictionary defaults, RouteValueDictionary constraints, IRouteHandler routeHandler); public Route(string url, RouteValueDictionary defaults, RouteValueDictionary constraints, RouteValueDictionary dataTokens, IRouteHandler routeHandler); public override RouteData GetRouteData(HttpContextBase httpContext); public override VirtualPathData GetVirtualPath(RequestContext requestContext, RouteValueDictionary values); protected virtual bool ProcessConstraint(HttpContextBase httpContext, object constraint, string parameterName, RouteValueDictionary values, RouteDirection routeDirection); private bool ProcessConstraints(HttpContextBase httpContext, RouteValueDictionary values, RouteDirection routeDirection); // Properties public RouteValueDictionary Constraints { get; set; } public RouteValueDictionary DataTokens { get; set; } public RouteValueDictionary Defaults { get; set; } public IRouteHandler RouteHandler { get; set; } public string Url { get; set; } }
Route添加了幾個屬性
Constraints:保存約束規則，最終保存為RouteValueDictionary
DataTokens:附加參數，指定controller的空間命名也放在這里。
Defaults:保存規則的默認值
url:規則URL
我們來看看GetRouteData，我們看看RouteData routeData=RouteCollection.GetRouteData(context)。
public RouteData GetRouteData(HttpContextBase httpContext) { if (httpContext == null) { throw new ArgumentNullException("httpContext"); } if (httpContext.Request == null) { throw new ArgumentException(RoutingResources.RouteTable_ContextMissingRequest, "httpContext"); } if (!this.RouteExistingFiles) { string appRelativeCurrentExecutionFilePath = httpContext.Request.AppRelativeCurrentExecutionFilePath; if (((appRelativeCurrentExecutionFilePath != "~/") && (this._vpp != null)) && (this._vpp.FileExists(appRelativeCurrentExecutionFilePath) || this._vpp.DirectoryExists(appRelativeCurrentExecutionFilePath))) { return null; } } using (this.GetReadLock()) { foreach (RouteBase base2 in this) { RouteData routeData = base2.GetRouteData(httpContext); if (routeData != null) { return routeData; } } } return null; }
上述代碼中最后通過遞歸遍歷自己所有的路由規則，分別調用我們所有注冊在RouteTable.Routes--->RouteCollection。
我們還注意到上面有這么一段：
{
string appRelativeCurrentExecutionFilePath = httpContext.Request.AppRelativeCurrentExecutionFilePath;
if (((appRelativeCurrentExecutionFilePath != "~/") && (this._vpp != null)) && (this._vpp.FileExists(appRelativeCurrentExecutionFilePath) || this._vpp.DirectoryExists(appRelativeCurrentExecutionFilePath)))
{
return null;
}
}
RouteCollection 有這么一個屬性RouteExistingFiles.當為false時，就檢測請求的路徑地址是否己經存在文件或目錄，如果存在，則直接不走路由了，直接返回null，默認就是false，我們可以實驗一下。當然這里是忽略了根目錄的，不然默認我們 http://www.xxx.com/ 也不能訪問了。
{
routes.IgnoreRoute("{resource}.axd/{*pathInfo}");
routes.MapRoute(
"Default", // Route name
"{controller}/{action}/{id}", // URL with parameters
new { controller = "Home", action = "Index", id = UrlParameter.Optional }, // Parameter defaults
new string[] { "MVCTest.Controllers" }
);
}
這里是默認的路由注冊，按理說我們訪問 home 時，會去到 home controller 的 index，但是我們在在項目里加一個 home 目錄，如下圖。
我們再訪問：http://localhost:2144/home/ 我們發現，無法找到該資源，也就是檢測到home這個目錄存在時，就不走路由了。
為尊重原創，本文的編寫參考了以下博文和文章：
程序園： http://www.cnblogs.com/lindaohui/archive/2012/08/31/2664047.html