為ASP.NET MVC及WebApi添加路由優先級

一、為什麼需要路由優先級

大家都知道我們在Asp.Net MVC項目或WebApi項目中注冊路由是沒有優先級的，當項目比較大、或有多個區域、或多個Web項目、或采用插件式框架開發時，我們的路由注冊很可能 不是寫在一個文件中的，而是分散在很多不同項目的文件中，這樣一來，路由的優先級的問題就突顯出來了。

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" } 
); 

假如是先注冊上面那個通用的default路由，再注冊這個login的路由，那麼無論怎麼樣，都會先匹配第一個滿足條件的路由，也就是第兩個路由注冊是無效的。
造成這個問題的原因就是這兩個路由注冊的順序問題，而Asp.Net MVC及WebApi中注冊路由都沒有優先級這個概念，所以今天我們就是要自己實現這個想法，在注冊路由時加入一個優先級的概念。

二、解決思路

1、先分析路由注冊的入口，比如我們新建一個mvc4.0的項目

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路由的注冊入口有兩個：
a. AreaRegistration.RegisterAllAreas();                                    注冊區域路由
b. RouteConfig.RegisterRoutes(RouteTable.Routes);          注冊項目路由

WebApi路由注冊入口有一個：
WebApiConfig.Register(GlobalConfiguration.Configuration);  注冊WebApi路由

2、注冊路由的處理類分析

AreaRegistrationContext
RouteCollection
HttpRouteCollection

注冊路由時主要是由這三個類來注冊處理路由的。

3、路由優先級方案

a、更改路由的注冊入口
b、自定義一個路由的結構類RoutePriority及HttpRoutePriority，這兩個類下面都有Priority這個屬性
c、自定一個RegistrationContext來注冊路由，注冊的對象為上述自定義路由。
d、所有的路由注冊完成之後再按優先順序添加到RouteCollection及HttpRouteCollection中實際生效。

三、具體實現

1、路由定義

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、定義路由注冊的接口

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

3、定義路由注冊上下文類

public class RegistrationContext 
{ 
  #region mvc 
  public List<RoutePriority> Routes = new List<RoutePriority>(); 
 
  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<string, object>; 
    if (dictionary != null) 
    { 
      return new RouteValueDictionary(dictionary); 
    } 
 
    return new RouteValueDictionary(values); 
  } 
  #endregion 
 
  #region http 
  public List<HttpRoutePriority> HttpRoutes = new List<HttpRoutePriority>(); 
 
  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、把路由注冊處理方法添加到Configuration類中

public static Configuration RegisterRoutePriority(this Configuration config) 
{ 
  var typesSoFar = new List<Type>(); 
  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<Assembly> GetReferencedAssemblies() 
{ 
  var assemblies = BuildManager.GetReferencedAssemblies(); 
  foreach (Assembly assembly in assemblies) 
    yield return assembly; 
} 
這樣一來就大功告成，使用時只需要在Global.asax.cs文件中修改原注冊入口為

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(); //注冊自定義路由 
  } 
} 
在每個項目中使用只需要要繼承自定義路由注冊接口IRouteRegister，例如：

public class Registration : IRouteRegister 
{ 
  public void Register(RegistrationContext context) 
  { 
    //注冊後端管理登錄路由 
    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 
   ); 
 
    //注冊後端管理頁面默認路由 
    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 
    ); 
 
    //注冊手機訪問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 
    ); 
  } 
} 

四、總結

當遇到大項目注冊的路由不生效時你應該要想到有可能是因為路由順序的原因，以上就是本文的全部內容，希望對大家的學習有所啟發。