[Web API] Web API 2 深入系列(1) 路由

ASP.NET 路由
- 注册路由
- 动态映射HttpHandler
WebAPI 路由
- 注册路由
- 调用GetRouteData
2个路由系统衔接
- GlobalConfiguration
- HostedHttpRoute
补充

路由是进入Web API的第一扇门.目的用于确定Controller名称、Action名称、路由参数.

ASP.NET 路由

注册路由

在ASP.NET中注册路由的方式:

RouteCollection.MapPageRoute()

添加1个完整的路由:

var defaults = new RouteValueDictionary//路由变量默认值

{

        {"code","010"},

        {"phone","1000000"},

};

var constraints = new RouteValueDictionary//路由变量约束

{

    {"code",@"0\d{2,3}" },

    {"phone",@"\d{7,9}" },

    {"httpMethod",new HttpMethodConstraint("POST") }

};

var dataTokens = new RouteValueDictionary//路由相关参数,不用于处理路由匹配功能

{

    {"defaultCode","北京" },

    {"defaultPhone","北京X电话" }

};

RouteTable.Routes.MapPageRoute("default", "{code}/{phone}", "~/call.aspx", false, defaults, constraints, dataTokens);

获取RouteCollection

一般通过RouteTable.Routes

public class RouteTable

{

    private static RouteCollection _instance = new RouteCollection();

    public static RouteCollection Routes { get { return RouteTable._instance; } }

}

路由:RouteBase

public abstract class RouteBase

{

  public bool RouteExistingFiles {get; set;} = true;//对现有文件进行路由

  public abstract RouteData GetRouteData(HttpContextBase httpContext);

  public abstract VirtualPathData GetVirtualPath(RequestContext requestContext, RouteValueDictionary values);

}

路由默认实现:Route

public class Route : RouteBase

{

    /// <summary>

    /// 路由约束

    /// </summary>

    public RouteValueDictionary Constraints { get; set; }

    /// <summary>

    /// 路由自定义参数(一般存储备注说明等)

    /// </summary>

    public RouteValueDictionary DataTokens { get; set; }

    /// <summary>

    /// 路由变量默认值

    /// </summary>

    public RouteValueDictionary Defaults { get; set; }

    /// <summary>

    /// 路由对应处理程序对象

    /// </summary>

    public IRouteHandler RouteHandler { get; set; }

    /// <summary>

    /// 路由模板

    /// </summary>

    public string Url { get; set; }

}

忽略路由:

忽略路由本质是添加一个StopRoutingHandler(返回空的HttpHandler)的路由

routes.Ignore("010/1000001");(路由先注册,先匹配)

routes.MapPageRoute("default", "{code}/{phone}", "~/call.aspx", false, defaults, constraints, dataTokens);

路由约束:

在上面完整的路由添加Demo中,路由约束有2种方式

正则表达式字符串
实现IRouteConstraint接口

动态映射HttpHandler

路由是通过UrlRoutingModule这个HttpModule实现动态拦截.

public virtual void PostResolveRequestCache(HttpContextBase context)

{

    RouteData routeData = RouteTable.Routes.GetRouteData(context);

    IRouteHandler routeHandler = routeData.RouteHandler;

    IHttpHandler httpHandler = routeHandler.GetHttpHandler(new RequestContext(context, routeData));

    context.RemapHandler(httpHandler);

}

WebAPI 路由

注册路由

在Web API中注册路由的方式:HttpRouteCollection.MapHttpRoute(),

这里重点看下MapHttpRoute方法内部

public static class HttpRouteCollectionExtensions

{

    public static IHttpRoute MapHttpRoute(this HttpRouteCollection routes, string name, string routeTemplate, object defaults, object constraints, HttpMessageHandler handler)

    {

        IHttpRoute route = routes.CreateRoute(routeTemplate, (IDictionary<string, object>)defaults, (IDictionary<string, object>)constraints, (IDictionary<string, object>)null, handler);

        routes.Add(name, route);

        return route;

    }

}

获取HttpRouteCollection

在WebAPI中通过HttpConfiguration的Routes属性

public class HttpConfiguration : IDisposable

{

    public Collection<DelegatingHandler> MessageHandlers { get; }

    public HttpRouteCollection Routes { get; }

    public ConcurrentDictionary<object, object> Properties { get; }

}

WebAPI路由:IHttpRoute

public interface IHttpRoute

{

  string RouteTemplate { get; }

  IDictionary<string, object> Defaults { get; }

  IDictionary<string, object> Constraints { get; }

  IDictionary<string, object> DataTokens { get; }

  HttpMessageHandler Handler { get; }

  IHttpRouteData GetRouteData(string virtualPathRoot, HttpRequestMessage request);

  IHttpVirtualPathData GetVirtualPath(HttpRequestMessage request, IDictionary<string, object> values);

}

WebAPI路由默认实现:HttpRoute

由于IHttpRoute设计的非常全,HttpRoute基本就是实现了IHttpRoute.

(这种设计上比RouteBase要优势很多)

调用GetRouteData

与ASP.NET稍微不同的是

直接对所有请求进行路由而不再判断是否文件存在.
添加一个VirtualPathRoot的过滤

public class HttpRouteCollection

{

    public virtual IHttpRouteData GetRouteData(HttpRequestMessage request)

    {

        string virtualPathRoot = request.GetRequestContext().VirtualPathRoot;

        IHttpRouteData routeData = this._collection[index].GetRouteData(virtualPathRoot, request);

        return routeData;

    }

}

2个路由系统衔接

Web API提供了一套自身的路由系统，所以不依赖于ASP.NET.

寄宿方式有多种.如果以WebHost的方式.本质上还是走的ASP.NET路由处理.

GlobalConfiguration

WebAPI的配置在HttpConfiguration中提供.

在WebHost中,定义了GlobalConfiguration用来创建HttpConfiguration

public static class GlobalConfiguration

{

public static HttpConfiguration Configuration = GlobalConfiguration.CreateConfiguration();//创建HttpConfiguration

public static HttpMessageHandler DefaultHandler = GlobalConfiguration.CreateDefaultHandler();//创建HttpRoutingDispatcher(WebAPI管道尾部HttpMessageHandler)

public static HttpServer DefaultServer = GlobalConfiguration.CreateDefaultServer();//创建HttpServer(WebAPI管道开头HttpMessageHandler)

public static void Configure(Action<HttpConfiguration> configurationCallback)//提供方便配置路由

{

    configurationCallback(GlobalConfiguration.Configuration);

}

private static Lazy<HttpConfiguration> CreateConfiguration()

{

    return new Lazy<HttpConfiguration>((Func<HttpConfiguration>) (() =>

    {

        //这里用HostedHttpRouteCollection实现HttpRouteCollection

        return new HttpConfiguration((HttpRouteCollection) new HostedHttpRouteCollection(RouteTable.Routes));

    }));

}

}

HostedHttpRoute

在GlobalConfiguration中创建的HttpConfiguration对象是用HostedHttpRouteCollection作为参数

这里我觉得有必要看下CreateRoute和Add方法

internal class HostedHttpRouteCollection : HttpRouteCollection

{

    //真正维护的路由集合

    private readonly RouteCollection _routeCollection;

    //创建路由 MapHttpRoute会调用该方法

    public override IHttpRoute CreateRoute(string uriTemplate, IDictionary<string, object> defaults, IDictionary<string, object> constraints, IDictionary<string, object> dataTokens, HttpMessageHandler handler)

    {

      return (IHttpRoute) new HostedHttpRoute(uriTemplate, defaults, constraints, dataTokens, handler);

    }

    public override void Add(string name, IHttpRoute route)

    {

        //只是添加到内部的routeCollection中

        //route.ToRoute() => route.OriginalRoute;

      this._routeCollection.Add(name, (RouteBase) route.ToRoute());

    }

    public override IHttpRouteData GetRouteData(HttpRequestMessage request)

    {

        //通过调用内部的Route的GetRouteData

        RouteData routeData = this._routeCollection.GetRouteData(httpContextBase);

        return (IHttpRouteData)new HostedHttpRouteData(routeData);

    }

}

而HostedHttpRoute在WebHost中

相当于用HttpRoute的身却提供了真正的Route

internal class HostedHttpRoute : IHttpRoute

{

    //ASP.NET Route

    internal Route OriginalRoute { get; private set; }

    public HostedHttpRoute(string uriTemplate, IDictionary<string, object> defaults, IDictionary<string, object> constraints, IDictionary<string, object> dataTokens, HttpMessageHandler handler)

    {

        //内部的OriginalRoute实际为HttpWebRoute

      this.OriginalRoute = (Route) new HttpWebRoute(uriTemplate, defaults1, constraints1, dataTokens1, <strong>(IRouteHandler) HttpControllerRouteHandler.Instance</strong>, (IHttpRoute) this);

      this.Handler = handler;

    }

}

从HostedHttpRoute构造函数中我们看到了真正的Route为HttpWebRoute 且RouteHandler为HttpControllerRouteHandler.Instance

public class HttpControllerRouteHandler : IRouteHandler

{

    public static HttpControllerRouteHandler Instance{ get { return new HttpControllerRouteHandler(); } }

    protected virtual IHttpHandler GetHttpHandler(RequestContext requestContext)

    {

        return (IHttpHandler) new HttpControllerHandler(requestContext.RouteData);

    }

}

补充

冗余的设计:

HttpRoute中Handler的HttpMessageHandler,未发现有任何地方使用到.
HttpRoute和Route中DataTokens,建议直接取消.

备注:

文章中的代码并非完整,一般是经过自己精简后的.
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