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為ASP.NET MVC及WebApi添加路由優(yōu)先級

更新時間：2015年10月15日 10:02:21 投稿：lijiao

這是一個對Asp.Net Mvc的一個很小的功能拓展，小項目可能不太需要這個功能，但有時候項目大了注冊的路由不生效時你應(yīng)該要想到有可能是因為路由順序的原因，這時這個路由優(yōu)先級的功能有可能就會給你帶來便利。

一、為什么需要路由優(yōu)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(yōu)先級的，當(dāng)項目比較大、或有多個區(qū)域、或多個Web項目、或采用插件式框架開發(fā)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(yōu)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，那么無論怎么樣，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(yōu)先級這個概念，所以今天我們就是要自己實現(xiàn)這個想法，在注冊路由時加入一個優(yōu)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(qū)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(yōu)先級方案

a、更改路由的注冊入口
b、自定義一個路由的結(jié)構(gòu)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后再按優(yōu)先順序添加到RouteCollection及HttpRouteCollection中實際生效。

三、具體實現(xiàn)

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) 
  { 
    //注冊后端管理登錄路由 
    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 
   ); 
 
    //注冊后端管理頁面默認(rèn)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(jié)

當(dāng)遇到大項目注冊的路由不生效時你應(yīng)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(nèi)容，希望對大家的學(xué)習(xí)有所啟發(fā)。

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