給ASP.NET MVC及WebApi新增路由優先順序

蕭秦的部落格發表於2015-07-09
ASP.NETMVCWebAPI路由

一、為什麼需要路由優先順序

大家都知道我們在Asp.Net MVC專案或WebApi專案中註冊路由是沒有優先順序的，當專案比較大、或有多個區域、或多個Web專案、或採用外掛式框架開發時，我們的路由註冊很可能不是寫在一個檔案中的，而是分散在很多不同專案的檔案中，這樣一來，路由的優先順序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" }
);

假如是先註冊上面那個通用的default路由，再註冊這個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，也就是第兩個路由註冊是無效的。
造成這個問題的原因就是這兩個路由註冊的順序問題，而Asp.Net MVC及WebApi中註冊路由都沒有優先順序這個概念，所以今天我們就是要自己實現這個想法，在註冊路由時加入一個優先順序的概念。

二、解決思路

1、先分析路由註冊的入口，比如我們新建一個mvc4.0的專案

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路由的註冊入口有兩個：
a. AreaRegistration.RegisterAllAreas();                            註冊區域路由
b. RouteConfig.RegisterRoutes(RouteTable.Routes);          註冊專案路由

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

2、註冊路由的處理類分析

AreaRegistrationContext
RouteCollection
HttpRouteCollection

註冊路由時主要是由這三個類來註冊處理路由的。

3、路由優先順序方案

a、更改路由的註冊入口
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來註冊路由，註冊的物件為上述自定義路由。
d、所有的路由註冊完成之後再按優先順序新增到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、定義路由註冊的介面

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

3、定義路由註冊上下文類

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、把路由註冊處理方法新增到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檔案中修改原註冊入口為

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(); //註冊自定義路由
    }
}

在每個專案中使用只需要要繼承自定義路由註冊介面IRouteRegister，例如：

public class Registration : IRouteRegister
{
    public void Register(RegistrationContext context)
    {
       //註冊後端管理登入路由
        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
      );

       //註冊後端管理頁面預設路由
        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
        );

       //註冊手機訪問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

這是一個對Asp.Net Mvc的一個很小的功能擴充，小專案可能不太需要這個功能，但有時候專案大了註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，這時這個路由優先順序的功能有可能就會給你帶來便利。總之共享給有需要的朋友們參考。

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