Asp.net MVC天生就有着漂亮的Url.但是却有别于Asp.net的UrlRewriter.那么其的实现原理是怎样的呢?这就要说到Route了.

Asp.net MVC的生命周期由8个步骤组成:

1.RouteTable(路由表)的创建

2.UrlRoutingMoudle请求拦截

3.Routing engine确定route

4.RouteHandler创建相关的IHttpHandler实例

5.IHttpHandler实例确定Controller(控制器)

6.Controller执行

7.视图引擎创建

8.视图呈现

这里主要讲解前4个.

RouteTable(路由表)的创建

打开Global.asax

class MvcApplication : System.Web.HttpApplication

 2: {

void RegisterRoutes(RouteCollection routes)

 4: {

);

 6:  

 7: routes.MapRoute(

// Route name

// URL with parameters

// Parameter defaults

}

 12: );

 13:  

 14: routes.MapRoute(

,

,

 },

 }

 19: );

 20: }

 21:  

void Application_Start()

 23: {

 24: AreaRegistration.RegisterAllAreas();

 25:  

 26: RegisterRoutes(RouteTable.Routes);

 27:  

//RouteDebug.RouteDebugger.RewriteRoutesForTesting(RouteTable.Routes);

 29: }

 30: }

在此,我们声明了两个Route.

在MVC1中.我们必须

new MvcRouteHandler()));

new MvcRouteHandler()));

new MvcRouteHandler()));

这样添加.但在.Net3.5中.我们却可以直接利用匿名类直接New一个.这是因为.Net3.5中扩展了一个MapRoute方法.该方法利用反射.进行背后的添加

string[] namespaces) {

null) {

);

 4: }

null) {

);

 7: }

 8:  

new MvcRouteHandler()) {

new RouteValueDictionary(defaults),

new RouteValueDictionary(constraints),

new RouteValueDictionary()

 13: };

 14:  

null) && (namespaces.Length > 0)) {

] = namespaces;

 17: }

 18:  

 19: routes.Add(name, route);

 20:  

return route;

 22: }

UrlRoutingMoudle请求拦截

按照MS惯例,一般会在WebConfig留下些蛛丝马迹,打开WebConfig.不出其然.我们发现HttpMoudle中有

/>

利用Reflector打开UrlRoutingModule类.

void Init(HttpApplication application)

 2: {

this.OnApplicationPostResolveRequestCache);

this.OnApplicationPostMapRequestHandler);

 5: }

 6:  

 7: 

Routing engine确定route

可以看到.在application的events中注册了PostResolveRequestCache 和PostMapRequestHandler 事件.

PostResolveRequestCache

void PostResolveRequestCache(HttpContextBase context)

 2: {

this.RouteCollection.GetRouteData(context);

null)

 5: {

 6: IRouteHandler routeHandler = routeData.RouteHandler;

null)

 8: {

object[0]));

 10: }

is StopRoutingHandler))

 12: {

new RequestContext(context, routeData);

 14: IHttpHandler httpHandler = routeHandler.GetHttpHandler(requestContext);

null)

 16: {

object[] { routeHandler.GetType() }));

 18: }

new RequestData { OriginalPath = context.Request.Path, HttpHandler = httpHandler };

);

 21: }

 22: }

 23: }

 24:  

 25: 

这里.首先通过RouteCollection.GetRouteData得到当前的RouteData,

UrlRoutingModule.RouteCollection

public RouteCollection RouteCollection

 2: {

 3: get

 4: {

null)

 6: {

this._routeCollection = RouteTable.Routes;

 8: }

this._routeCollection;

 10: }

 11: set

 12: {

value;

 14: }

 15: }

 16: 

module中的RouteCollection只是很简单的引用了RouteTable中的静态实例Routes而已.

RouteTable

class RouteTable

 2: {

// Fields

new RouteCollection();

 5:  

// Properties

static RouteCollection Routes

 8: {

 9: get

 10: {

return _instance;

 12: }

 13: }

 14: }

RouteCollection.GetRouteData

这是获取RouteDate的核心实现.

public RouteData GetRouteData(HttpContextBase httpContext)

 2: {

null)

 4: {

);

 6: }

null)

 8: {

);

 10: }

this.RouteExistingFiles)

 12: {

string appRelativeCurrentExecutionFilePath = httpContext.Request.AppRelativeCurrentExecutionFilePath;

this._vpp.DirectoryExists(appRelativeCurrentExecutionFilePath)))

 15: {

null;

 17: }

 18: }

//线程锁

 20: {

//遍历当前集合中的所有RouteBase

 22: {

//调用RouteBase的RouteData.此处传入的Class是Route.

null)

 25: {

return routeData;

 27: }

 28: }

 29: }

null;

 31: }

 32:  

Route

Route继承至RouteBase.Route中提供了MVC的Route信息.

可以看到最后承载Route数据的容器是RouteVallueDictionary.Route中包含了该Dictionary

RouteData

RouteData的实现很简单.就提供了几个基本的字段而已.主要用于描述当前Route数据的信息.如此一来.我们可以得到当前Url所匹配的Route.

class RouteData

 2: {

// Fields

private RouteValueDictionary _dataTokens;

private IRouteHandler _routeHandler;

private RouteValueDictionary _values;

 7:  

// Methods

public RouteData();

public RouteData(RouteBase route, IRouteHandler routeHandler);

string valueName);

 12:  

// Properties

public RouteValueDictionary DataTokens { get; }

public RouteBase Route { get; set; }

public IRouteHandler RouteHandler { get; set; }

public RouteValueDictionary Values { get; }

 18: }

RouteHandler创建相关的IHttpHandler实例

RouteHandler

得到RouteData之后.获取RouteData之中的RouteHandler.根据RouteHandler获取相关的IHttpHandler.这样.MVC的Route隐射阶段就已经完成

new RequestContext(context, routeData);

 2: IHttpHandler httpHandler = routeHandler.GetHttpHandler(requestContext);

后面就是Controller的确定和执行了.