[Web API] Web API 2 深入系列(1) 路由

目录

1. ASP.NET 路由

   • 注册路由

   • 动态映射HttpHandler

2. WebAPI 路由

   • 注册路由

   • 调用GetRouteData

3. 2个路由系统衔接

   • GlobalConfiguration

   • HostedHttpRoute

4. 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",@"0d{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

1. 正则表达式字符串
2. 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

1. 直接对所有请求进行路由 而不再判断是否文件存在.
2. 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.

• 本篇内容使用MarkDown语法编辑

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