mvc5中webapi的路由

1.Global.asax中路由的注册

public class WebApiApplication : System.Web.HttpApplication
    {

        protected void Application_Start()
        {
            AreaRegistration.RegisterAllAreas();
　　　　　　　　//api路由注册
            GlobalConfiguration.Configure(WebApiConfig.Register);
            FilterConfig.RegisterGlobalFilters(GlobalFilters.Filters);
            RouteConfig.RegisterRoutes(RouteTable.Routes);
            BundleConfig.RegisterBundles(BundleTable.Bundles);
        }

    }

2.GlobalConfiguration源码

public static void Configure(Action<HttpConfiguration> configurationCallback)
        {
            if (configurationCallback == null)
            {
                throw new ArgumentNullException("configurationCallback");
            }
　　　　　　　　//执行WebApiConfig.Register方法并传入参数GlobalConfiguration.Configuration
            configurationCallback(GlobalConfiguration.Configuration);
            GlobalConfiguration.Configuration.EnsureInitialized();
        }

(1)参数GlobalConfiguration.Configuration

.public static HttpConfiguration Configuration
        {
            get
            {
                return GlobalConfiguration._configuration.Value;
            }
        }
.private static Lazy<HttpConfiguration> _configuration = GlobalConfiguration.CreateConfiguration();

.private static Lazy<HttpConfiguration> CreateConfiguration()
        {
            Func<HttpConfiguration> arg_1F_0;
            if ((arg_1F_0 = GlobalConfiguration.<>c.<>9__11_0) == null)
            {
                arg_1F_0 = (GlobalConfiguration.<>c.<>9__11_0 = new Func<HttpConfiguration>(GlobalConfiguration.<>c.<>9.<CreateConfiguration>b__11_0));
            }
            return new Lazy<HttpConfiguration>(arg_1F_0);
        }

.[CompilerGenerated]
        [Serializable]
        private sealed class <>c
        {
            public static readonly GlobalConfiguration.<>c <> = new GlobalConfiguration.<>c();
　　　　　　　　....internal HttpConfiguration <CreateConfiguration>b__11_0()
            {
　　　　　　　　　　//RouteTable.Routes全局路由变量
                HttpConfiguration expr_0F = new HttpConfiguration(new HostedHttpRouteCollection(RouteTable.Routes));
                ServicesContainer services = expr_0F.Services;
                services.Replace(typeof(IAssembliesResolver), new WebHostAssembliesResolver());
                services.Replace(typeof(IHttpControllerTypeResolver), new WebHostHttpControllerTypeResolver());
                services.Replace(typeof(IHostBufferPolicySelector), new WebHostBufferPolicySelector());
                services.Replace(typeof(IExceptionHandler), new WebHostExceptionHandler(services.GetExceptionHandler()));
                return expr_0F;
            }

        }

(2)WebApiConfig.Register方法

public static class WebApiConfig
    {
        public static void Register(HttpConfiguration config)
        {
            // Web API 配置和服务

            // Web API 路由
            config.MapHttpAttributeRoutes();

            config.Routes.MapHttpRoute(
                name: "DefaultApi",
                routeTemplate: "api/{controller}/{id}",
                defaults: new { id = RouteParameter.Optional }
            );
        }
    }

由参数可知config.Routes为HostedHttpRouteCollection类型

对应MapHttpRoute方法

public static IHttpRoute MapHttpRoute(this HttpRouteCollection routes, string name, string routeTemplate, object defaults, object constraints, HttpMessageHandler handler)
        {
            if (routes == null)
            {
                throw Error.ArgumentNull("routes");
            }
            HttpRouteValueDictionary defaults2 = new HttpRouteValueDictionary(defaults);
            HttpRouteValueDictionary constraints2 = new HttpRouteValueDictionary(constraints);
　　　　　　//1.封装单个路由
            IHttpRoute httpRoute = routes.CreateRoute(routeTemplate, defaults2, constraints2, null, handler);
　　　　　　//2.把路由加入HostedHttpRouteCollection中
　　　　　　　　routes.Add(name, httpRoute);
            return httpRoute;
        }

//1.封装单个路由 routes.CreateRoute方法

public override IHttpRoute CreateRoute(string uriTemplate, IDictionary<string, object> defaults, IDictionary<string, object> constraints, IDictionary<string, object> dataTokens, HttpMessageHandler handler)
{
    if (constraints != null)
    {
        foreach (KeyValuePair<string, object> current in constraints)
        {
            this.ValidateConstraint(uriTemplate, current.Key, current.Value);
        }
    }
    return new HostedHttpRoute(uriTemplate, defaults, constraints, dataTokens, handler);
}

可知HostedHttpRouteCollection中类型为HostedHttpRoute类型

//2.把路由加入HostedHttpRouteCollection中routes.Add方法

public override void Add(string name, IHttpRoute route)
        {
            this._routeCollection.Add(name, route.ToRoute());
        }

从参数第4步可知_routeCollection为全局变量RouteTable.Routes中

所以webapi中路由的注册实际最后也是注册到RouteTable.Routes全局变量中

3.webapi的routehandler

根据前边可知webapi的路由最后同mvc一样都是注册到全局路由变量中,在路由中通过urlRoutingModule获取请求然后转发到对应的handler中,那么webapi对应的routehandler是什么呢?

(1).从注册的单个路由类HostedHttpRoute中

从注册路由的maphttpRoute方法中

public static IHttpRoute MapHttpRoute(this HttpRouteCollection routes, string name, string routeTemplate, object defaults)
        {
            return routes.MapHttpRoute(name, routeTemplate, defaults, null, null);
        }

public static IHttpRoute MapHttpRoute(this HttpRouteCollection routes, string name, string routeTemplate, object defaults, object constraints)
        {
            return routes.MapHttpRoute(name, routeTemplate, defaults, constraints, null);
        }

public static IHttpRoute MapHttpRoute(this HttpRouteCollection routes, string name, string routeTemplate, object defaults, object constraints, HttpMessageHandler handler)
        {
            if (routes == null)
            {
                throw Error.ArgumentNull("routes");
            }
            HttpRouteValueDictionary defaults2 = new HttpRouteValueDictionary(defaults);
            HttpRouteValueDictionary constraints2 = new HttpRouteValueDictionary(constraints);
            IHttpRoute httpRoute = routes.CreateRoute(routeTemplate, defaults2, constraints2, null, handler);
            routes.Add(name, httpRoute);
            return httpRoute;
        }

传入的handler参数都为null

在routes.CreateRoute方法中生成HostedHttpRoute调用构造函数时传入的也是null

public static IHttpRoute MapHttpRoute(this HttpRouteCollection routes, string name, string routeTemplate, object defaults, object constraints, HttpMessageHandler handler)
        {
           .....
　　　　　　//1.封装单个路由
            IHttpRoute httpRoute = routes.CreateRoute(routeTemplate, defaults2, constraints2, null, handler);
　　　　　　　.....
        }
public override IHttpRoute CreateRoute(string uriTemplate, IDictionary<string, object> defaults, IDictionary<string, object> constraints, IDictionary<string, object> dataTokens, HttpMessageHandler handler)
{
   .......
    return new HostedHttpRoute(uriTemplate, defaults, constraints, dataTokens, handler);
}

HostedHttpRoute的构造函数

public HostedHttpRoute(string uriTemplate, IDictionary<string, object> defaults, IDictionary<string, object> constraints, IDictionary<string, object> dataTokens, HttpMessageHandler handler)
        {
            RouteValueDictionary defaults2 = (defaults != null) ? new RouteValueDictionary(defaults) : null;
            RouteValueDictionary constraints2 = (constraints != null) ? new RouteValueDictionary(constraints) : null;
            RouteValueDictionary dataTokens2 = (dataTokens != null) ? new RouteValueDictionary(dataTokens) : null;
            this.OriginalRoute = new HttpWebRoute(uriTemplate, defaults2, constraints2, dataTokens2, HttpControllerRouteHandler.Instance, this);
            this.Handler = handler;
        }

hostedHttpRoute中的getdata通过调用OriginalRoute属性获取对应的routedata.

综上:webapi对应的routehandler为HttpControllerRouteHandler

可知:webapi对应的routehandler为httpControllerRouteHandler

4 webapi对应的handler

从httpControllerRouteHandler中

protected virtual IHttpHandler GetHttpHandler(RequestContext requestContext)
        {
            return new HttpControllerHandler(requestContext.RouteData);
        }

获得HttpControllerHandler.