asp net core中的路由地址指的是(Asp.NetCoreEndPoint)

Asp.Net Core EndPoint 终点路由工作原理解读

一、背景

在本打算写一篇关于Identityserver4 的文章时候,却发现自己对EndPoint -终结点路由还不是很了解,故暂时先放弃了IdentityServer4 的研究和编写;所以才产生了今天这篇关于EndPoint (终结点路由) 的文章。

还是跟往常一样,打开电脑使用强大的Google 和百度搜索引擎查阅相关资料,以及打开Asp.net core 3.1 的源代码进行拜读,同时终于在我的实践及测试中对EndPoint 有了不一样的认识,说到这里更加敬佩微软对Asp.net core 3.x 的框架中管道模型的设计。

我先来提出以下几个问题:

1.当访问一个Web 应用地址时,Asp.Net Core 是怎么执行到Controller 的Action的呢?2.Endpoint 跟普通路由又存在着什么样的关系?3.UseRouing() 、UseAuthorization()、UserEndpoints() 这三个中间件的关系是什么呢?4.怎么利用Endpoint 编写自己的中间件以及Endpoint 的应用场景(时间有限,下回分享整理)

二、拜读源码解惑

Startup 代码

我们先来看一下Startup中简化版的代码,代码如下:

public void Configureservices(IServiceCollection services){ services.AddControllers();}public void Configure(IApplicationBuilder app, IWebHostEnvironment env){ app.UseRouting(); app.UseAuthorization(); app.UseEndpoints(endpoints => { endpoints.MapControllers(); });}

程序启动阶段:

•第一步:执行services.AddControllers() 将Controller的核心服务注册到容器中去•第二步:执行app.UseRouting() 将EndpointRoutingMiddleware中间件注册到http管道中•第三步:执行app.UseAuthorization() 将AuthorizationMiddleware中间件注册到http管道中•第四步:执行app.UseEndpoints(encpoints=>endpoints.MapControllers()) 有两个主要的作用:调用endpoints.MapControllers()将本程序集定义的所有Controller和Action转换为一个个的EndPoint放到路由中间件的配置对象RouteOptions中 将EndpointMiddleware中间件注册到http管道中

app.UseRouting() 源代码如下:

public static IApplicationBuilder UseRouting(this IApplicationBuilder builder){ if (builder == null) { throw new ArgumentNullException(nameof(builder)); } VerifyRoutingServicesAreRegistered(builder); var endpointRouteBuilder = new DefaultEndpointRouteBuilder(builder); builder.Properties[EndpointRouteBuilder] = endpointRouteBuilder; return builder.UseMiddleware<EndpointRoutingMiddleware>(endpointRouteBuilder); }

EndpointRoutingMiddleware 中间件代码如下:

internal sealed class EndpointRoutingMiddleware { private const string DiagnosticsEndpointMatchedKey = "Microsoft.AspNetCore.Routing.EndpointMatched"; private readonly MatcherFactory _matcherFactory; private readonly ILogger _logger; private readonly EndpointDataSource _endpointDataSource; private readonly DiagnosticListener _diagnosticListener; private readonly RequestDelegate _next; private Task<Matcher> _initializationTask; public EndpointRoutingMiddleware( MatcherFactory matcherFactory, ILogger<EndpointRoutingMiddleware> logger, IEndpointRouteBuilder endpointRouteBuilder, DiagnosticListener diagnosticListener, RequestDelegate next) { if (endpointRouteBuilder == null) { throw new ArgumentNullException(nameof(endpointRouteBuilder)); } _matcherFactory = matcherFactory ?? throw new ArgumentNullException(nameof(matcherFactory)); _logger = logger ?? throw new ArgumentNullException(nameof(logger)); _diagnosticListener = diagnosticListener ?? throw new ArgumentNullException(nameof(diagnosticListener)); _next = next ?? throw new ArgumentNullException(nameof(next)); _endpointDataSource = new CompositeEndpointDataSource(endpointRouteBuilder.DataSources); } public Task Invoke(HttpContext httpContext) { // Theres already an endpoint, skip maching completely var endpoint = httpContext.GetEndpoint(); if (endpoint != null) { Log.MatchSkipped(_logger, endpoint); return _next(httpContext); } // Theres an inherent race condition between waiting for init and accessing the matcher // this is OK because once `_matcher` is initialized, it will not be set to null again. var matcherTask = InitializeAsync(); if (!matcherTask.IsCompletedSuccessfully) { return AwaitMatcher(this, httpContext, matcherTask); } var matchTask = matcherTask.Result.MatchAsync(httpContext); if (!matchTask.IsCompletedSuccessfully) { return AwaitMatch(this, httpContext, matchTask); } return SetRoutingAndContinue(httpContext); // Awaited fallbacks for when the Tasks do not synchronously complete static async Task AwaitMatcher(EndpointRoutingMiddleware middleware, HttpContext httpContext, Task<Matcher> matcherTask) { var matcher = await matcherTask; await matcher.MatchAsync(httpContext); await middleware.SetRoutingAndContinue(httpContext); } static async Task AwaitMatch(EndpointRoutingMiddleware middleware, HttpContext httpContext, Task matchTask) { await matchTask; await middleware.SetRoutingAndContinue(httpContext); } } [MethodImpl(MethodImplOptions.AggressiveInlining)] private Task SetRoutingAndContinue(HttpContext httpContext) { // If there was no mutation of the endpoint then log failure var endpoint = httpContext.GetEndpoint(); if (endpoint == null) { Log.MatchFailure(_logger); } else { // Raise an event if the route matched if (_diagnosticListener.IsEnabled() && _diagnosticListener.IsEnabled(DiagnosticsEndpointMatchedKey)) { // Were just going to send the HttpContext since it has all of the relevant information _diagnosticListener.Write(DiagnosticsEndpointMatchedKey, httpContext); } Log.MatchSuccess(_logger, endpoint); } return _next(httpContext); } // Initialization is async to avoid blocking threads while reflection and things // of that nature take place. // // Weve seen cases where startup is very slow if we allow multiple threads to race // while initializing the set of endpoints/routes. Doing CPU intensive work is a // blocking operation if you have a low core count and enough work to do. private Task<Matcher> InitializeAsync() { var initializationTask = _initializationTask; if (initializationTask != null) { return initializationTask; } return InitializeCoreAsync(); } private Task<Matcher> InitializeCoreAsync() { var initialization = new TaskCompletionSource<Matcher>(TaskCreationOptions.RunContinuationsAsynchronously); var initializationTask = Interlocked.CompareExchange(ref _initializationTask, initialization.Task, null); if (initializationTask != null) { // This thread lost the race, join the existing task. return initializationTask; } // This thread won the race, do the initialization. try { var matcher = _matcherFactory.CreateMatcher(_endpointDataSource); // Now replace the initialization task with one created with the default execution context. // This is important because capturing the execution context will leak memory in ASP.NET Core. using (ExecutionContext.SuppressFlow()) { _initializationTask = Task.FromResult(matcher); } // Complete the task, this will unblock any requests that came in while initializing. initialization.SetResult(matcher); return initialization.Task; } catch (Exception ex) { // Allow initialization to occur again. Since DataSources can change, its possible // for the developer to correct the data causing the failure. _initializationTask = null; // Complete the task, this will throw for any requests that came in while initializing. initialization.SetException(ex); return initialization.Task; } } private static class Log { private static readonly Action<ILogger, string, Exception> _matchSuccess = LoggerMessage.Define<string>( LogLevel.Debug, new EventId(1, "MatchSuccess"), "Request matched endpoint {EndpointName}"); private static readonly Action<ILogger, Exception> _matchFailure = LoggerMessage.Define( LogLevel.Debug, new EventId(2, "MatchFailure"), "Request did not match any endpoints"); private static readonly Action<ILogger, string, Exception> _matchingSkipped = LoggerMessage.Define<string>( LogLevel.Debug, new EventId(3, "MatchingSkipped"), "Endpoint {EndpointName} already set, skipping route matching."); public static void MatchSuccess(ILogger logger, Endpoint endpoint) { _matchSuccess(logger, endpoint.DisplayName, null); } public static void MatchFailure(ILogger logger) { _matchFailure(logger, null); } public static void MatchSkipped(ILogger logger, Endpoint endpoint) { _matchingSkipped(logger, endpoint.DisplayName, null); } } }

我们从它的源码中可以看到,EndpointRoutingMiddleware中间件先是创建matcher,然后调用matcher.MatchAsync(httpContext)去寻找Endpoint,最后通过httpContext.GetEndpoint()验证了是否已经匹配到了正确的Endpoint并交个下个中间件继续执行!

app.UseEndpoints() 源代码

public static IApplicationBuilder UseEndpoints(this IApplicationBuilder builder, Action<IEndpointRouteBuilder> configure){ if (builder == null) { throw new ArgumentNullException(nameof(builder)); } if (configure == null) { throw new ArgumentNullException(nameof(configure)); } VerifyRoutingServicesAreRegistered(builder); VerifyEndpointRoutingMiddlewareIsRegistered(builder, out var endpointRouteBuilder); configure(endpointRouteBuilder); // Yes, this mutates an IOptions. Were registering data sources in a global collection which // can be used for discovery of endpoints or URL generation. // // Each middleware gets its own collection of data sources, and all of those data sources also // get added to a global collection. var routeOptions = builder.ApplicationServices.GetRequiredService<IOptions<RouteOptions>>(); foreach (var dataSource in endpointRouteBuilder.DataSources) { routeOptions.Value.EndpointDataSources.Add(dataSource); } return builder.UseMiddleware<EndpointMiddleware>();}internal class DefaultEndpointRouteBuilder : IEndpointRouteBuilder{ public DefaultEndpointRouteBuilder(IApplicationBuilder applicationBuilder) { ApplicationBuilder = applicationBuilder ?? throw new ArgumentNullException(nameof(applicationBuilder)); DataSources = new List<EndpointDataSource>(); } public IApplicationBuilder ApplicationBuilder { get; } public IApplicationBuilder CreateApplicationBuilder() => ApplicationBuilder.New(); public ICollection<EndpointDataSource> DataSources { get; } public IServiceProvider ServiceProvider => ApplicationBuilder.ApplicationServices; }

代码中构建了DefaultEndpointRouteBuilder 终结点路由构建者对象,该对象中存储了Endpoint的集合数据;同时把终结者路由集合数据存储在了routeOptions 中,并注册了EndpointMiddleware 中间件到http管道中; Endpoint对象代码如下:

/// <summary>/// Represents a logical endpoint in an application./// </summary>public class Endpoint{ /// <summary> /// Creates a new instance of <see cref="Endpoint"/>. /// </summary> /// <param name="requestDelegate">The delegate used to process requests for the endpoint.</param> /// <param name="metadata"> /// The endpoint <see cref="EndpointMetadataCollection"/>. May be null. /// </param> /// <param name="displayName"> /// The informational display name of the endpoint. May be null. /// </param> public Endpoint( RequestDelegate requestDelegate, EndpointMetadataCollection metadata, string displayName) { // All are allowed to be null RequestDelegate = requestDelegate; Metadata = metadata ?? EndpointMetadataCollection.Empty; DisplayName = displayName; } /// <summary> /// Gets the informational display name of this endpoint. /// </summary> public string DisplayName { get; } /// <summary> /// Gets the collection of metadata associated with this endpoint. /// </summary> public EndpointMetadataCollection Metadata { get; } /// <summary> /// Gets the delegate used to process requests for the endpoint. /// </summary> public RequestDelegate RequestDelegate { get; } public override string ToString() => DisplayName ?? base.ToString(); }

Endpoint 对象代码中有两个关键类型属性分别是EndpointMetadataCollection 类型和RequestDelegate:

•EndpointMetadataCollection:存储了Controller 和Action相关的元素集合,包含Action 上的Attribute 特性数据等•RequestDelegate :存储了Action 也即委托,这里是每一个Controller 的Action 方法

再回过头来看看EndpointMiddleware 中间件和核心代码,EndpointMiddleware 的一大核心代码主要是执行Endpoint 的RequestDelegate 委托,也即Controller 中的Action 的执行。

public Task Invoke(HttpContext httpContext){ var endpoint = httpContext.GetEndpoint(); if (endpoint?.RequestDelegate != null) { if (!_routeOptions.SuppressCheckForUnhandledSecurityMetadata) { if (endpoint.Metadata.GetMetadata<IAuthorizeData>() != null && !httpContext.Items.ContainsKey(AuthorizationMiddlewareInvokedKey)) { ThrowMissingAuthMiddlewareException(endpoint); } if (endpoint.Metadata.GetMetadata<ICorsMetadata>() != null && !httpContext.Items.ContainsKey(CorsMiddlewareInvokedKey)) { ThrowMissingCorsMiddlewareException(endpoint); } } Log.ExecutingEndpoint(_logger, endpoint); try { var requestTask = endpoint.RequestDelegate(httpContext); if (!requestTask.IsCompletedSuccessfully) { return AwaitRequestTask(endpoint, requestTask, _logger); } } catch (Exception exception) { Log.ExecutedEndpoint(_logger, endpoint); return Task.FromException(exception); } Log.ExecutedEndpoint(_logger, endpoint); return Task.CompletedTask; } return _next(httpContext); static async Task AwaitRequestTask(Endpoint endpoint, Task requestTask, ILogger logger) { try { await requestTask; } finally { Log.ExecutedEndpoint(logger, endpoint); } }}

疑惑解答:

1. 当访问一个Web 应用地址时,Asp.Net Core 是怎么执行到Controller 的Action的呢?

答:程序启动的时候会把所有的Controller 中的Action 映射存储到routeOptions 的集合中,Action 映射成Endpoint终结者 的RequestDelegate 委托属性,最后通过UseEndPoints 添加EndpointMiddleware 中间件进行执行,同时这个中间件中的Endpoint 终结者路由已经是通过Rouing匹配后的路由。

2. EndPoint 跟普通路由又存在着什么样的关系?

答:Ednpoint 终结者路由是普通路由map 转换后的委托路由,里面包含了路由方法的所有元素信息EndpointMetadataCollection 和RequestDelegate 委托。

3. UseRouing() 、UseAuthorization()、UseEndpoints() 这三个中间件的关系是什么呢?

答:UseRouing 中间件主要是路由匹配,找到匹配的终结者路由Endpoint ;UseEndpoints 中间件主要针对UseRouing 中间件匹配到的路由进行 委托方法的执行等操作。 UseAuthorization 中间件主要针对 UseRouing 中间件中匹配到的路由进行拦截 做授权验证操作等,通过则执行下一个中间件UseEndpoints(),具体的关系可以看下面的流程图:

asp net core中的路由地址指的是(Asp.NetCoreEndPoint)(1)

上面流程图中省略了一些部分,主要是把UseRouing 、UseAuthorization 、UseEndpoint 这三个中间件的关系突显出来。

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