动手写一个简版 asp.net core
Intro
之前看到过蒋金楠老师的一篇 200 行代码带你了解 asp.net core 框架,最近参考蒋老师和 Edison 的文章和代码,结合自己对 asp.net core 的理解 ,最近自己写了一个 MiniAspNetCore ,写篇文章总结一下。
HttpContext
HttpContext
可能是最为常用的一个类了, HttpContext
是请求上下文,包含了所有的请求信息以及响应信息,以及一些自定义的用于在不同中间件中传输数据的信息
来看一下 HttpContext
的定义:
public class HttpContext
{public IServiceProvider RequestServices { get; set; }public HttpRequest Request { get; set; }public HttpResponse Response { get; set; }public IFeatureCollection Features { get; set; }public HttpContext(IFeatureCollection featureCollection){Features = featureCollection;Request = new HttpRequest(featureCollection);Response = new HttpResponse(featureCollection);}
}
HttpRequest
即为请求信息对象,包含了所有请求相关的信息,
HttpResponse
为响应信息对象,包含了请求对应的响应信息
RequestServices
为 asp.net core 里的 RequestServices
,代表当前请求的服务提供者,可以使用它来获取具体的服务实例
Features
为 asp.net core 里引入的对象,可以用来在不同中间件中传递信息和用来解耦合
,下面我们就来看下 HttpRequest
和 HttpResponse
是怎么实现的
HttpRequest:
public class HttpRequest
{private readonly IRequestFeature _requestFeature;public HttpRequest(IFeatureCollection featureCollection){_requestFeature = featureCollection.Get<IRequestFeature>();}public Uri Url => _requestFeature.Url;public NameValueCollection Headers => _requestFeature.Headers;public string Method => _requestFeature.Method;public string Host => _requestFeature.Url.Host;public Stream Body => _requestFeature.Body;
}
HttpResponse:
public class HttpResponse
{private readonly IResponseFeature _responseFeature;public HttpResponse(IFeatureCollection featureCollection){_responseFeature = featureCollection.Get<IResponseFeature>();}public bool ResponseStarted => _responseFeature.Body.Length > 0;public int StatusCode{get => _responseFeature.StatusCode;set => _responseFeature.StatusCode = value;}public async Task WriteAsync(byte[] responseBytes){if (_responseFeature.StatusCode <= 0){_responseFeature.StatusCode = 200;}if (responseBytes != null && responseBytes.Length > 0){await _responseFeature.Body.WriteAsync(responseBytes);}}
}
Features
上面我们提供我们可以使用 Features
在不同中间件中传递信息和解耦合
由上面 HttpRequest
/ HttpResponse
的代码我们可以看出来, HttpRequest
和 HttpResponse
其实就是在 IRequestFeature
和 IResponseFeature
的基础上封装了一层,真正的核心其实是 IRequestFeature
/ IResponseFeature
,而这里使用接口就很好的实现了解耦,可以根据不同的 WebServer 使用不同的 RequestFeature
/ ResponseFeature
,来看下 IRequestFeature
/ IResponseFeature
的实现
public interface IRequestFeature
{Uri Url { get; }string Method { get; }NameValueCollection Headers { get; }Stream Body { get; }
}
public interface IResponseFeature
{public int StatusCode { get; set; }NameValueCollection Headers { get; set; }public Stream Body { get; }
}
这里的实现和 asp.net core 的实际的实现方式应该不同,asp.net core 里 Headers 同一个 Header 允许有多个值,asp.net core 里是 StringValues 来实现的,这里简单处理了,使用了一个
NameValueCollection
对象
上面提到的 Features
是一个 IFeatureCollection
对象,相当于是一系列的 Feature
对象组成的,来看下 FeatureCollection
的定义:
public interface IFeatureCollection : IDictionary<Type, object> { }
public class FeatureCollection : Dictionary<Type, object>, IFeatureCollection
{
}
这里 IFeatureCollection
直接实现 IDictionary<Type,object>
,通过一个字典 Feature 类型为 Key,Feature 对象为 Value 的字典来保存
为了方便使用,可以定义两个扩展方法来方便的Get/Set
public static class FeatureExtensions
{public static IFeatureCollection Set<TFeature>(this IFeatureCollection featureCollection, TFeature feature){featureCollection[typeof(TFeature)] = feature;return featureCollection;}public static TFeature Get<TFeature>(this IFeatureCollection featureCollection){var featureType = typeof(TFeature);return featureCollection.ContainsKey(featureType) ? (TFeature)featureCollection[featureType] : default(TFeature);}
}
Web服务器
上面我们已经提到了 Web 服务器通过 IRequestFeature
/ IResponseFeature
来实现不同 web 服务器和应用程序的解耦,web 服务器只需要提供自己的 RequestFeature
/ ResponseFeature
即可
为了抽象不同的 Web 服务器,我们需要定义一个 IServer
的抽象接口,定义如下:
public interface IServer
{Task StartAsync(Func<HttpContext, Task> requestHandler, CancellationToken cancellationToken = default);
}
IServer
定义了一个 StartAsync
方法,用来启动 Web服务器,
StartAsync
方法有两个参数,一个是 requestHandler,是一个用来处理请求的委托,另一个是取消令牌用来停止 web 服务器
示例使用了 HttpListener
来实现了一个简单 Web 服务器, HttpListenerServer
定义如下:
public class HttpListenerServer : IServer
{private readonly HttpListener _listener;private readonly IServiceProvider _serviceProvider;public HttpListenerServer(IServiceProvider serviceProvider, IConfiguration configuration){_listener = new HttpListener();var urls = configuration.GetAppSetting("ASPNETCORE_URLS")?.Split(';');if (urls != null && urls.Length > 0){foreach (var url in urls.Where(u => u.IsNotNullOrEmpty()).Select(u => u.Trim()).Distinct()){// Prefixes must end in a forward slash ("/")// https://stackoverflow.com/questions/26157475/use-of-httplistener_listener.Prefixes.Add(url.EndsWith("/") ? url : $"{url}/");}}else{_listener.Prefixes.Add("http://localhost:5100/");}_serviceProvider = serviceProvider;}public async Task StartAsync(Func<HttpContext, Task> requestHandler, CancellationToken cancellationToken = default){_listener.Start();if (_listener.IsListening){Console.WriteLine("the server is listening on ");Console.WriteLine(_listener.Prefixes.StringJoin(","));}while (!cancellationToken.IsCancellationRequested){var listenerContext = await _listener.GetContextAsync();var featureCollection = new FeatureCollection();featureCollection.Set(listenerContext.GetRequestFeature());featureCollection.Set(listenerContext.GetResponseFeature());using (var scope = _serviceProvider.CreateScope()){var httpContext = new HttpContext(featureCollection){RequestServices = scope.ServiceProvider,};await requestHandler(httpContext);}listenerContext.Response.Close();}_listener.Stop();}
}
HttpListenerServer
实现的 RequestFeature
/ ResponseFeatue
public class HttpListenerRequestFeature : IRequestFeature
{private readonly HttpListenerRequest _request;public HttpListenerRequestFeature(HttpListenerContext listenerContext){_request = listenerContext.Request;}public Uri Url => _request.Url;public string Method => _request.HttpMethod;public NameValueCollection Headers => _request.Headers;public Stream Body => _request.InputStream;
}
public class HttpListenerResponseFeature : IResponseFeature
{private readonly HttpListenerResponse _response;public HttpListenerResponseFeature(HttpListenerContext httpListenerContext){_response = httpListenerContext.Response;}public int StatusCode { get => _response.StatusCode; set => _response.StatusCode = value; }public NameValueCollection Headers{get => _response.Headers;set{_response.Headers = new WebHeaderCollection();foreach (var key in value.AllKeys)_response.Headers.Add(key, value[key]);}}public Stream Body => _response.OutputStream;
}
为了方便使用,为 HttpListenerContext
定义了两个扩展方法,就是上面 HttpListenerServer
中的 GetRequestFeature
/ GetResponseFeature
:
public static class HttpListenerContextExtensions
{public static IRequestFeature GetRequestFeature(this HttpListenerContext context){return new HttpListenerRequestFeature(context);}public static IResponseFeature GetResponseFeature(this HttpListenerContext context){return new HttpListenerResponseFeature(context);}
}
RequestDelegate
在上面的 IServer
定义里有一个 requestHandler 的 对象,在 asp.net core 里是一个名称为 RequestDelegate
的对象,而用来构建这个委托的在 asp.net core 里是 IApplicationBuilder
,这些在蒋老师和 Edison 的文章和代码里都可以看到,这里我们只是简单介绍下,我在 MiniAspNetCore 的示例中没有使用这些对象,而是使用了自己抽象的 PipelineBuilder
和原始委托实现的
asp.net core 里 RequestDelegate
定义:
public delegate Task RequestDelegate(HttpContext context);
其实和我们上面定义用的 Func<HttpContext,Task>
是等价的
IApplicationBuilder
定义:
/// <summary>
/// Defines a class that provides the mechanisms to configure an application's request pipeline.
/// </summary>
public interface IApplicationBuilder
{/// <summary>/// Gets or sets the <see cref="T:System.IServiceProvider" /> that provides access to the application's service container./// </summary>IServiceProvider ApplicationServices { get; set; }/// <summary>/// Gets the set of HTTP features the application's server provides./// </summary>IFeatureCollection ServerFeatures { get; }/// <summary>/// Gets a key/value collection that can be used to share data between middleware./// </summary>IDictionary<string, object> Properties { get; }/// <summary>/// Adds a middleware delegate to the application's request pipeline./// </summary>/// <param name="middleware">The middleware delegate.</param>/// <returns>The <see cref="T:Microsoft.AspNetCore.Builder.IApplicationBuilder" />.</returns>IApplicationBuilder Use(Func<RequestDelegate, RequestDelegate> middleware);/// <summary>/// Creates a new <see cref="T:Microsoft.AspNetCore.Builder.IApplicationBuilder" /> that shares the <see cref="P:Microsoft.AspNetCore.Builder.IApplicationBuilder.Properties" /> of this/// <see cref="T:Microsoft.AspNetCore.Builder.IApplicationBuilder" />./// </summary>/// <returns>The new <see cref="T:Microsoft.AspNetCore.Builder.IApplicationBuilder" />.</returns>IApplicationBuilder New();/// <summary>/// Builds the delegate used by this application to process HTTP requests./// </summary>/// <returns>The request handling delegate.</returns>RequestDelegate Build();
}
我们这里没有定义 IApplicationBuilder
,使用了简化抽象的 IAsyncPipelineBuilder
,定义如下:
public interface IAsyncPipelineBuilder<TContext>
{IAsyncPipelineBuilder<TContext> Use(Func<Func<TContext, Task>, Func<TContext, Task>> middleware);Func<TContext, Task> Build();IAsyncPipelineBuilder<TContext> New();
}
对于 asp.net core 的中间件来说 ,上面的 TContext
就是 HttpContext
,替换之后也就是下面这样的:
public interface IAsyncPipelineBuilder<HttpContext>
{IAsyncPipelineBuilder<HttpContext> Use(Func<Func<HttpContext, Task>, Func<HttpContext, Task>> middleware);Func<HttpContext, Task> Build();IAsyncPipelineBuilder<HttpContext> New();
}
是不是和 IApplicationBuilder
很像,如果不像可以进一步把 Func<HttpContext,Task>
使用 RequestDelegate
替换
public interface IAsyncPipelineBuilder<HttpContext>
{IAsyncPipelineBuilder<HttpContext> Use(Func<RequestDelegate, RequestDelegate> middleware);RequestDelegate Build();IAsyncPipelineBuilder<HttpContext> New();
}
最后再将接口名称替换一下:
public interface IApplicationBuilder1
{IApplicationBuilder1 Use(Func<RequestDelegate, RequestDelegate> middleware);RequestDelegate Build();IApplicationBuilder1 New();
}
至此,就完全可以看出来了,这 IAsyncPipelineBuilder<HttpContext>
就是一个简版的 IApplicationBuilder
IAsyncPipelineBuilder
和 IApplicationBuilder
的作用是将注册的多个中间件构建成一个请求处理的委托
中间件处理流程:
更多关于 PipelineBuilder 构建中间件的信息可以查看 让 .NET 轻松构建中间件模式代码 了解更多
WebHost
通过除了 Web 服务器之外,还有一个 Web Host 的概念,可以简单的这样理解,一个 Web 服务器上可以有多个 Web Host,就像 IIS/nginx (Web Server) 可以 host 多个站点
可以说 WebHost 离我们的应用更近,所以我们还需要 IHost
来托管应用
public interface IHost
{Task RunAsync(CancellationToken cancellationToken = default);
}
WebHost
定义:
public class WebHost : IHost
{private readonly Func<HttpContext, Task> _requestDelegate;private readonly IServer _server;public WebHost(IServiceProvider serviceProvider, Func<HttpContext, Task> requestDelegate){_requestDelegate = requestDelegate;_server = serviceProvider.GetRequiredService<IServer>();}public async Task RunAsync(CancellationToken cancellationToken = default){await _server.StartAsync(_requestDelegate, cancellationToken).ConfigureAwait(false);}
}
为了方便的构建 Host
对象,引入了 HostBuilder
来方便的构建一个 Host
,定义如下:
public interface IHostBuilder
{IHostBuilder ConfigureConfiguration(Action<IConfigurationBuilder> configAction);IHostBuilder ConfigureServices(Action<IConfiguration, IServiceCollection> configureAction);IHostBuilder Initialize(Action<IConfiguration, IServiceProvider> initAction);IHostBuilder ConfigureApplication(Action<IConfiguration, IAsyncPipelineBuilder<HttpContext>> configureAction);IHost Build();
}
WebHostBuilder
:
public class WebHostBuilder : IHostBuilder
{private readonly IConfigurationBuilder _configurationBuilder = new ConfigurationBuilder();private readonly IServiceCollection _serviceCollection = new ServiceCollection();private Action<IConfiguration, IServiceProvider> _initAction = null;private readonly IAsyncPipelineBuilder<HttpContext> _requestPipeline = PipelineBuilder.CreateAsync<HttpContext>(context =>{context.Response.StatusCode = 404;return Task.CompletedTask;});public IHostBuilder ConfigureConfiguration(Action<IConfigurationBuilder> configAction){configAction?.Invoke(_configurationBuilder);return this;}public IHostBuilder ConfigureServices(Action<IConfiguration, IServiceCollection> configureAction){if (null != configureAction){var configuration = _configurationBuilder.Build();configureAction.Invoke(configuration, _serviceCollection);}return this;}public IHostBuilder ConfigureApplication(Action<IConfiguration, IAsyncPipelineBuilder<HttpContext>> configureAction){if (null != configureAction){var configuration = _configurationBuilder.Build();configureAction.Invoke(configuration, _requestPipeline);}return this;}public IHostBuilder Initialize(Action<IConfiguration, IServiceProvider> initAction){if (null != initAction){_initAction = initAction;}return this;}public IHost Build(){var configuration = _configurationBuilder.Build();_serviceCollection.AddSingleton<IConfiguration>(configuration);var serviceProvider = _serviceCollection.BuildServiceProvider();_initAction?.Invoke(configuration, serviceProvider);return new WebHost(serviceProvider, _requestPipeline.Build());}public static WebHostBuilder CreateDefault(string[] args){var webHostBuilder = new WebHostBuilder();webHostBuilder.ConfigureConfiguration(builder => builder.AddJsonFile("appsettings.json", true, true)).UseHttpListenerServer();return webHostBuilder;}
}
这里的示例我在
IHostBuilder
里增加了一个Initialize
的方法来做一些初始化的操作,我觉得有些数据初始化配置初始化等操作应该在这里操作,而不应该在Startup
的Configure
方法里处理,这样Configure
方法可以更纯粹一些,只配置 asp.net core 的请求管道,这纯属个人意见,没有对错之分这里 Host 的实现和 asp.net core 的实现不同,有需要的可以深究源码,在 asp.net core 2.x 的版本里是有一个
IWebHost
的,在 asp.net core 3.x 以及 .net 5 里是没有IWebHost
的取而代之的是通用主机IHost
, 通过实现了一个IHostedService
来实现WebHost
的
Run
运行示例代码:
public class Program
{private static readonly CancellationTokenSource Cts = new CancellationTokenSource();public static async Task Main(string[] args){Console.CancelKeyPress += OnExit;var host = WebHostBuilder.CreateDefault(args).ConfigureServices((configuration, services) =>{}).ConfigureApplication((configuration, app) =>{app.When(context => context.Request.Url.PathAndQuery.StartsWith("/favicon.ico"), pipeline => { });app.When(context => context.Request.Url.PathAndQuery.Contains("test"),p => { p.Run(context => context.Response.WriteAsync("test")); });app.Use(async (context, next) =>{await context.Response.WriteLineAsync($"middleware1, requestPath:{context.Request.Url.AbsolutePath}");await next();}).Use(async (context, next) =>{await context.Response.WriteLineAsync($"middleware2, requestPath:{context.Request.Url.AbsolutePath}");await next();}).Use(async (context, next) =>{await context.Response.WriteLineAsync($"middleware3, requestPath:{context.Request.Url.AbsolutePath}");await next();});app.Run(context => context.Response.WriteAsync("Hello Mini Asp.Net Core"));}).Initialize((configuration, services) =>{}).Build();await host.RunAsync(Cts.Token);}private static void OnExit(object sender, EventArgs e){Console.WriteLine("exiting ...");Cts.Cancel();}
}
在示例项目目录下执行 dotnet run
,并访问 http://localhost:5100/
:
仔细观察浏览器 console
或 network
的话,会发现还有一个请求,浏览器会默认请求 /favicon.ico
获取网站的图标
因为我们针对这个请求没有任何中间件的处理,所以直接返回了 404
在访问 /test
,可以看到和刚才的输出完全不同,因为这个请求走了另外一个分支,相当于 asp.net core 里 Map
/ MapWhen
的效果,另外 Run
代表里中间件的中断,不会执行后续的中间件
More
上面的实现只是我在尝试写一个简版的 asp.net core 框架时的实现,和 asp.net core 的实现并不完全一样,如果需要请参考源码,上面的实现仅供参考,上面实现的源码可以在 Github 上获取 https://github.com/WeihanLi/SamplesInPractice/tree/master/MiniAspNetCore
asp.net core 源码:https://github.com/dotnet/aspnetcore
Reference
https://www.cnblogs.com/artech/p/inside-asp-net-core-framework.html
https://www.cnblogs.com/artech/p/mini-asp-net-core-3x.html
https://www.cnblogs.com/edisonchou/p/aspnet_core_mini_implemention_introduction.html
让 .NET 轻松构建中间件模式代码
让 .NET 轻松构建中间件模式代码(二)
https://github.com/WeihanLi/SamplesInPractice/tree/master/MiniAspNetCore