如何为ASP.NET MVC及WebApi添加路由优先级

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一、为什么需要路由优先级

大家都知道我们在Asp.Net MVC项目或WebApi项目中注册路由是没有优先级的，当项目比较大、或有多个区域、或多个Web项目、或采用插件式框架开发时，我们的路由注册很可能 不是写在一个文件中的，而是分散在很多不同项目的文件中，这样一来，路由的优先级的问题就突显出来了。

比如： App_Start/RouteConfig.cs中

routes.MapRoute(   name: "Default",   url: "{controller}/{action}/{id}",   defaults: new { controller = "Home", action = "Index", id = UrlParameter.Optional } );  Areas/Admin/AdminAreaRegistration.cs中  context.MapRoute(   name: "Login",    url: "login",   defaults: new { area = "Admin", controller = "Account", action = "Login", id = UrlParameter.Optional },   namespaces: new string[] { "Wenku.Admin.Controllers" } );

假如是先注册上面那个通用的default路由，再注册这个login的路由，那么无论怎么样，都会先匹配第一个满足条件的路由，也就是第两个路由注册是无效的。
造成这个问题的原因就是这两个路由注册的顺序问题，而Asp.Net MVC及WebApi中注册路由都没有优先级这个概念，所以今天我们就是要自己实现这个想法，在注册路由时加入一个优先级的概念。

二、解决思路

1、先分析路由注册的入口，比如我们新建一个mvc4.0的项目

public class MvcApplication : System.Web.HttpApplication {   protected void Application_Start()   {     AreaRegistration.RegisterAllAreas();      WebApiConfig.Register(GlobalConfiguration.Configuration);     FilterConfig.RegisterGlobalFilters(GlobalFilters.Filters);     RouteConfig.RegisterRoutes(RouteTable.Routes);   } }

Mvc路由的注册入口有两个：
a. AreaRegistration.RegisterAllAreas(); 注册区域路由
b. RouteConfig.RegisterRoutes(RouteTable.Routes); 注册项目路由

WebApi路由注册入口有一个：
WebApiConfig.Register(GlobalConfiguration.Configuration); 注册WebApi路由

2、注册路由的处理类分析

AreaRegistrationContext
RouteCollection
HttpRouteCollection

注册路由时主要是由这三个类来注册处理路由的。

3、路由优先级方案

a、更改路由的注册入口
b、自定义一个路由的结构类RoutePriority及HttpRoutePriority，这两个类下面都有Priority这个属性
c、自定一个RegistrationContext来注册路由，注册的对象为上述自定义路由。
d、所有的路由注册完成之后再按优先顺序添加到RouteCollection及HttpRouteCollection中实际生效。

三、具体实现

1、路由定义

public class RoutePriority : Route {   public string Name { get; set; }   public int Priority { get; set; }    public RoutePriority(string url, IRouteHandler routeHandler)     : base(url,routeHandler)   {    } }  public class HttpRoutePriority {   public string Name { get; set; }   public int Priority { get; set; }   public string RouteTemplate{get;set;}   public object Defaults{get;set;}   public object Constraints{get;set;}   public HttpMessageHandler Handler{get;set;} }

2、定义路由注册的接口

public interface IRouteRegister {   void Register(RegistrationContext context); }

3、定义路由注册上下文类

public class RegistrationContext {   #region mvc   public List Routes = new List();    public RoutePriority MapRoute(string name, string url,int priority=0)   {     return MapRoute(name, url, (object)null /* defaults */, priority);   }    public RoutePriority MapRoute(string name, string url, object defaults, int priority = 0)   {     return MapRoute(name, url, defaults, (object)null /* constraints */, priority);   }    public RoutePriority MapRoute(string name, string url, object defaults, object constraints, int priority = 0)   {     return MapRoute(name, url, defaults, constraints, null /* namespaces */, priority);   }    public RoutePriority MapRoute(string name, string url, string[] namespaces, int priority = 0)   {     return MapRoute(name, url, (object)null /* defaults */, namespaces, priority);   }    public RoutePriority MapRoute(string name, string url, object defaults, string[] namespaces,int priority=0)   {     return MapRoute(name, url, defaults, null /* constraints */, namespaces, priority);   }    public RoutePriority MapRoute(string name, string url, object defaults, object constraints, string[] namespaces, int priority = 0)   {     var route = MapPriorityRoute(name, url, defaults, constraints, namespaces, priority);     var areaName = GetAreaName(defaults);     route.DataTokens["area"] = areaName;      // disabling the namespace lookup fallback mechanism keeps this areas from accidentally picking up     // controllers belonging to other areas     bool useNamespaceFallback = (namespaces == null || namespaces.Length == 0);     route.DataTokens["UseNamespaceFallback"] = useNamespaceFallback;      return route;   }    private static string GetAreaName(object defaults)   {     if (defaults != null)     {       var property = defaults.GetType().GetProperty("area");       if (property != null)         return (string)property.GetValue(defaults, null);     }      return null;   }    private RoutePriority MapPriorityRoute(string name, string url, object defaults, object constraints, string[] namespaces,int priority)   {     if (url == null)     {       throw new ArgumentNullException("url");     }      var route = new RoutePriority(url, new MvcRouteHandler())     {       Name = name,       Priority = priority,       Defaults = CreateRouteValueDictionary(defaults),       Constraints = CreateRouteValueDictionary(constraints),       DataTokens = new RouteValueDictionary()     };      if ((namespaces != null) && (namespaces.Length > 0))     {       route.DataTokens["Namespaces"] = namespaces;     }      Routes.Add(route);     return route;   }    private static RouteValueDictionary CreateRouteValueDictionary(object values)   {     var dictionary = values as IDictionary;     if (dictionary != null)     {       return new RouteValueDictionary(dictionary);     }      return new RouteValueDictionary(values);   }   #endregion    #region http   public List HttpRoutes = new List();    public HttpRoutePriority MapHttpRoute(string name, string routeTemplate, int priority = 0)   {     return MapHttpRoute(name, routeTemplate, defaults: null, constraints: null, handler: null, priority: priority);   }    public HttpRoutePriority MapHttpRoute(string name, string routeTemplate, object defaults, int priority = 0)   {     return MapHttpRoute(name, routeTemplate, defaults, constraints: null, handler: null, priority: priority);   }    public HttpRoutePriority MapHttpRoute(string name, string routeTemplate, object defaults, object constraints, int priority = 0)   {     return MapHttpRoute(name, routeTemplate, defaults, constraints, handler: null, priority: priority);   }    public HttpRoutePriority MapHttpRoute(string name, string routeTemplate, object defaults, object constraints, HttpMessageHandler handler, int priority = 0)   {     var httpRoute = new HttpRoutePriority();     httpRoute.Name = name;     httpRoute.RouteTemplate = routeTemplate;     httpRoute.Defaults = defaults;     httpRoute.Constraints = constraints;     httpRoute.Handler = handler;     httpRoute.Priority = priority;     HttpRoutes.Add(httpRoute);      return httpRoute;   }   #endregion }

4、把路由注册处理方法添加到Configuration类中

public static Configuration RegisterRoutePriority(this Configuration config) {   var typesSoFar = new List();   var assemblies = GetReferencedAssemblies();   foreach (Assembly assembly in assemblies)   {     var types = assembly.GetTypes().Where(t => typeof(IRouteRegister).IsAssignableFrom(t) && !t.IsAbstract && !t.IsInterface);     typesSoFar.AddRange(types);   }    var context = new RegistrationContext();   foreach (var type in typesSoFar)   {     var obj = (IRouteRegister)Activator.CreateInstance(type);     obj.Register(context);   }    foreach (var route in context.HttpRoutes.OrderByDescending(x => x.Priority))     GlobalConfiguration.Configuration.Routes.MapHttpRoute(route.Name, route.RouteTemplate, route.Defaults, route.Constraints, route.Handler);    foreach (var route in context.Routes.OrderByDescending(x => x.Priority))     RouteTable.Routes.Add(route.Name, route);    return config; }  private static IEnumerable GetReferencedAssemblies() {   var assemblies = BuildManager.GetReferencedAssemblies();   foreach (Assembly assembly in assemblies)     yield return assembly; } 这样一来就大功告成，使用时只需要在Global.asax.cs文件中修改原注册入口为public class MvcApplication : System.Web.HttpApplication {   protected void Application_Start()   {     WebApiConfig.Register(GlobalConfiguration.Configuration);     FilterConfig.RegisterGlobalFilters(GlobalFilters.Filters);     RouteConfig.RegisterRoutes(RouteTable.Routes);      Configuration.Instance()       .RegisterComponents()       .RegisterRoutePriority(); //注册自定义路由   } } 在每个项目中使用只需要要继承自定义路由注册接口IRouteRegister，例如：public class Registration : IRouteRegister {   public void Register(RegistrationContext context)   {     //注册后端管理登录路由     context.MapRoute(      name: "Admin_Login",      url: "Admin/login",      defaults: new { area = "Admin", controller = "Account", action = "Login", id = UrlParameter.Optional },      namespaces: new string[] { "Wenku.Admin.Controllers" },      priority: 11    );      //注册后端管理页面默认路由     context.MapRoute(       name: "Admin_default",       url: "Admin/{controller}/{action}/{id}",       defaults: new { area = "Admin", controller = "Home", action = "Index", id = UrlParameter.Optional },       namespaces: new string[] { "Wenku.Admin.Controllers" },       priority: 10     );      //注册手机访问WebApi路由     context.MapHttpRoute(       name: "Mobile_Api",       routeTemplate: "api/mobile/{controller}/{action}/{id}",       defaults: new       {         area = "mobile",         action = RouteParameter.Optional,         id = RouteParameter.Optional,         namespaceName = new string[] { "Wenku.Mobile.Http" }       },       constraints: new { action = new StartWithConstraint() },       priority: 0     );   } }

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