MVC路由解析---MapRoute

文章引导

引言

前面我们讲了IgnoreRoute链接

现在我们讲讲核心的MapRoute，还是提前准备Reflection工具，若是没准备，可以看“”MVC路由深入详解1---IgnoreRoute”中的System.Web.dll源码

一.RouteCollection

我们来看看RouteCollection.MapRoute，截图如下：

相信大家看到了RouteCollectionExtensions是一个静态类，是对RouteCollection的扩展（关于扩展方法的大家可以百度，此处不做详细描述）。好家伙，我们看看这个扩展方法走向何方（这个时候就是Reflection发挥作用的时候了）。

引用“”MVC路由深入详解1---IgnoreRoute”中的内容，看看MapRoute的参数传入的是什么：

name: "Default"

url: "{controller}/{action}/{id}"

defaults: new { controller = "Home", action = "Index", id = UrlParameter.Optional } --->这是个匿名类型

我们看看扩展方法去了哪里：

public static Route MapRoute(this RouteCollection routes, string name, string url, object defaults) => routes.MapRoute(name, url, defaults, null);

我们接着往下走

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 > ))

            {

                route.DataTokens["Namespaces"] = param;

            }

            Add(name, route);

            return route;

        }

上面新建了一个Route,Route就是一条具体的路由，new Route(url, new MvcRouteHandler())传入规则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

我们继续拆解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:在派生类重写时，设置支持HTTP请求所必须的会话状态行为的类型

            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是对Dictionary<string,object>进行包装，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);

        }

    }

}

我们来看看效果

五.Add(name,route)

我们来看看这个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;

            }

        }

里面做了重复路由名称验证，Add方法的第二个参数是RouteBase,我们看看MapRoute方法里传入给Add方法的参数是Route。Route是继承于RouteBase，RouteBase是一个抽象类，这个类是为继承类服务的，里面定义了GetRouteData和GetVirtualPath两个抽象方法。

GetRouteData：解析请求url，提取数据，如：/home/index 得到：controller/home,action/index提取得到的数据会包装成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添加了几个属性

Constraints:保存约束规则，最终保存为RouteValueDictionary

DataTokens:附加参数，指定controller的空间命名也放在这里。

Defaults:保存规则的默认值

url:规则URL

我们来看看GetRouteData，我们看看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;

}

上述代码中最后通过递归遍历自己所有的路由规则，分别调用我们所有注册在RouteTable.Routes--->RouteCollection。

我们还注意到上面有这么一段：

if (!this.RouteExistingFiles)
    {
        string appRelativeCurrentExecutionFilePath = httpContext.Request.AppRelativeCurrentExecutionFilePath;
        if (((appRelativeCurrentExecutionFilePath != "~/") && (this._vpp != null)) && (this._vpp.FileExists(appRelativeCurrentExecutionFilePath) || this._vpp.DirectoryExists(appRelativeCurrentExecutionFilePath)))
        {
            return null;
        }
    }

RouteCollection 有这么一个属性RouteExistingFiles.当为false时，就检测请求的路径地址是否己经存在文件或目录，如果存在，则直接不走路由了，直接返回null，默认就是false，我们可以实验一下。当然这里是忽略了根目录的，不然默认我们 http://www.xxx.com/ 也不能访问了。

public static void RegisterRoutes(RouteCollection routes)
{
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" }
            );
        }

这里是默认的路由注册，按理说我们访问 home 时，会去到 home controller 的 index，但是我们在在项目里加一个 home 目录，如下图。

我们再访问：http://localhost:2144/home/ 我们发现，无法找到该资源，也就是检测到home这个目录存在时，就不走路由了。

为尊重原创，本文的编写参考了以下博文和文章：

程序园： http://www.cnblogs.com/lindaohui/archive/2012/08/31/2664047.html