深圳住房和建设局网站预约放号,网站开发数据交互,word模板免费网站,北京家装设计师排名作为ASP.NET Core请求处理管道的“龙头”的服务器负责监听和接收请求并最终完成对请求的响应。它将原始的请求上下文描述为相应的特性#xff08;Feature#xff09;#xff0c;并以此将HttpContext上下文创建出来#xff0c;中间件针对HttpContext上下文的所有操作将借助于…作为ASP.NET Core请求处理管道的“龙头”的服务器负责监听和接收请求并最终完成对请求的响应。它将原始的请求上下文描述为相应的特性Feature并以此将HttpContext上下文创建出来中间件针对HttpContext上下文的所有操作将借助于这些特性转移到原始的请求上下文上。学习ASP.NET Core框架最有效的方式就是按照它的原理“再造”一个框架了解服务器的本质最好的手段就是试着自定义一个服务器。现在我们自定义一个真正的服务器。在此之前我们再来回顾一下表示服务器的IServer接口。[本文节选《ASP.NET Core 6框架揭秘》第18章]一、IServer二、请求和响应特性三、StreamBodyFeature四、HttpListenerServer一、IServer作为服务器的IServer对象利用如下所示的Features属性提供了与自身相关的特性。除了利用StartAsyncTContext和StopAsync方法启动和关闭服务器之外它还实现了IDisposable接口资源的释放工作可以通过实现的Dispose方法来完成。StartAsyncTContext方法将IHttpApplicationTContext类型的参数作为处理请求的“应用”该对象是对中间件管道的封装。从这个意义上讲服务器就是传输层和这个IHttpApplicationTContext对象之间的“中介”。public interface IServer : IDisposable
{IFeatureCollection Features { get; }Task StartAsyncTContext(IHttpApplicationTContext application, CancellationToken cancellationToken) where TContext : notnull;Task StopAsync(CancellationToken cancellationToken);
}虽然不同服务器类型的定义方式千差万别但是背后的模式基本上与下面这个以伪代码定义的服务器类型一致。如下这个Server利用IListener对象来监听和接收请求该对象是利用构造函数中注入的IListenerFactory工厂根据指定的监听地址创建出来的。StartAsyncTContext方法从Features特性集合中提取出IServerAddressesFeature特性并针对它提供的每个监听地址创建一个IListener对象。该方法为每个IListener对象开启一个“接收和处理请求”的循环循环中的每次迭代都会调用IListener对象的AcceptAsync方法来接收请求我们利用RequestContext对象来表示请求上下文。public class Server : IServer
{private readonly IListenerFactory _listenerFactory;private readonly ListIListener _listeners new();public IFeatureCollection Features { get; } new FeatureCollection();public Server(IListenerFactory listenerFactory) _listenerFactory listenerFactory;public async Task StartAsyncTContext(IHttpApplicationTContext application, CancellationToken cancellationToken) where TContext : notnull{var addressFeature Features.GetIServerAddressesFeature()!;foreach (var address in addressFeature.Addresses){var listener await _listenerFactory.BindAsync(address);_listeners.Add(listener);_ StartAcceptLoopAsync(listener);}async Task StartAcceptLoopAsync(IListener listener){while (true){var requestContext await listener.AcceptAsync();_ ProcessRequestAsync(requestContext);}}async Task ProcessRequestAsync(RequestContext requestContext){var feature new RequestContextFeature(requestContext);var contextFeatures new FeatureCollection();contextFeatures.SetIHttpRequestFeature(feature);contextFeatures.SetIHttpResponseFeature(feature);contextFeatures.SetIHttpResponseBodyFeature(feature);var context application.CreateContext(contextFeatures);Exception? exception null;try{await application.ProcessRequestAsync(context);}catch (Exception ex){exception ex;}finally{application.DisposeContext(context, exception);}}}public Task StopAsync(CancellationToken cancellationToken) Task.WhenAll(_listeners.Select(listener listener.StopAsync()));public void Dispose() _listeners.ForEach(listener listener.Dispose());
}public interface IListenerFactory
{TaskIListener BindAsync(string listenAddress);
}public interface IListener : IDisposable
{TaskRequestContext AcceptAsync();Task StopAsync();
}public class RequestContext
{...
}public class RequestContextFeature : IHttpRequestFeature, IHttpResponseFeature, IHttpResponseBodyFeature
{public RequestContextFeature(RequestContext requestContext);...
}StartAsyncTContext方法接下来利用此RequestContext上下文将RequestContextFeature特性创建出来。RequestContextFeature特性类型同时实现了IHttpRequestFeature, IHttpResponseFeature和 IHttpResponseBodyFeature这三个核心接口我们特性针对这三个接口将特性对象添加到创建的FeatureCollection集合中。特性集合随后作为参数调用IHttpApplicationTContext的CreateContext方法将TContext上下文创建出来后者将进一步作为参数调用另一个ProcessRequestAsync方法将请求分发给中间件管道进行处理。待处理结束IHttpApplicationTContext对象的DisposeContext方法被调用创建的TContext上下文承载的资源得以释放。二、请求和响应特性接下来我们将采用类似的模式来定义一个基于HttpListener的服务器。提供的HttpListenerServer的思路就是利用自定义特性来封装表示原始请求上下文的HttpListenerContext对象我们使用HttpRequestFeature和HttpResponseFeature这个两个现成特性。public class HttpRequestFeature : IHttpRequestFeature
{public string Protocol { get; set; }public string Scheme { get; set; }public string Method { get; set; }public string PathBase { get; set; }public string Path { get; set; }public string QueryString { get; set; }public string RawTarget { get; set; }public IHeaderDictionary Headers { get; set; }public Stream Body { get; set; }
}public class HttpResponseFeature : IHttpResponseFeature
{public int StatusCode { get; set; }public string? ReasonPhrase { get; set; }public IHeaderDictionary Headers { get; set; }public Stream Body { get; set; }public virtual bool HasStarted false;public HttpResponseFeature(){StatusCode 200;Headers new HeaderDictionary();Body Stream.Null;}public virtual void OnStarting(Funcobject, Task callback, object state) { }public virtual void OnCompleted(Funcobject, Task callback, object state) { }
}如果我们使用HttpRequestFeature来描述请求意味着HttpListener在接受到请求之后需要将请求信息从HttpListenerContext上下文转移到该特性上。如果使用HttpResponseFeature来描述响应待中间件管道在完成针对请求的处理后我们还需要将该特性承载的响应数据应用到HttpListenerContext上下文上。三、StreamBodyFeature现在我们有了描述请求和响应的两个特性还需要一个描述响应主体的特性为此我们定义了如下这个StreamBodyFeature特性类型。StreamBodyFeature直接使用构造函数提供的Stream对象作为响应主体的输出流并根据该对象创建出Writer属性返回的PipeWriter对象。本着“一切从简”的原则我们并没有实现用来发送文件的SendFileAsync方法其他成员也采用最简单的方式进行了实现。public class StreamBodyFeature : IHttpResponseBodyFeature
{public Stream Stream { get; }public PipeWriter Writer { get; }public StreamBodyFeature(Stream stream){Stream stream;Writer PipeWriter.Create(Stream);}public Task CompleteAsync() Task.CompletedTask;public void DisableBuffering() { }public Task SendFileAsync(string path, long offset, long? count, CancellationToken cancellationToken default) throw new NotImplementedException();public Task StartAsync(CancellationToken cancellationToken default) Task.CompletedTask;
}四、HttpListenerServer在如下这个自定义的HttpListenerServer服务器类型中与传输层交互的HttpListener体现在_listener字段上。服务器在初始化过程中它的Features属性返回的IFeatureCollection对象中添加了一个ServerAddressesFeature特性因为我们需要用它来存放注册的监听地址。实现StartAsyncTContext方法将监听地址从这个特性中取出来应用到HttpListener对象上。public class HttpListenerServer : IServer
{private readonly HttpListener _listener new();public IFeatureCollection Features { get; } new FeatureCollection();public HttpListenerServer() Features.SetIServerAddressesFeature(new ServerAddressesFeature());public Task StartAsyncTContext(IHttpApplicationTContext application,CancellationToken cancellationToken) where TContext : notnull{var pathbases new HashSetstring(StringComparer.OrdinalIgnoreCase);var addressesFeature Features .GetIServerAddressesFeature()!;foreach (string address in addressesFeature.Addresses){_listener.Prefixes.Add(address.TrimEnd(/) /);pathbases.Add(new Uri(address).AbsolutePath.TrimEnd(/));}_listener.Start();while (true){var listenerContext _listener.GetContext();_ ProcessRequestAsync(listenerContext);}async Task ProcessRequestAsync( HttpListenerContext listenerContext){FeatureCollection features new();var requestFeature CreateRequestFeature(pathbases, listenerContext);var responseFeature new HttpResponseFeature();var body new MemoryStream();var bodyFeature new StreamBodyFeature(body);features.SetIHttpRequestFeature(requestFeature);features.SetIHttpResponseFeature(responseFeature);features.SetIHttpResponseBodyFeature(bodyFeature);var context application.CreateContext(features);Exception? exception null;try{await application.ProcessRequestAsync(context);var response listenerContext.Response;response.StatusCode responseFeature.StatusCode;if (responseFeature.ReasonPhrase is not null){response.StatusDescription responseFeature.ReasonPhrase;}foreach (var kv in responseFeature.Headers){response.AddHeader(kv.Key, kv.Value);}body.Position 0;await body.CopyToAsync(listenerContext.Response.OutputStream);}catch (Exception ex){exception ex;}finally{body.Dispose();application.DisposeContext(context, exception);listenerContext.Response.Close();}}}public void Dispose() _listener.Stop();private static HttpRequestFeature CreateRequestFeature(HashSetstring pathbases,HttpListenerContext listenerContext){var request listenerContext.Request;var url request.Url!;var absolutePath url.AbsolutePath;var protocolVersion request.ProtocolVersion;var requestHeaders new HeaderDictionary();foreach (string key in request.Headers){requestHeaders.Add(key, request.Headers.GetValues(key));}var requestFeature new HttpRequestFeature{Body request.InputStream,Headers requestHeaders,Method request.HttpMethod,QueryString url.Query,Scheme url.Scheme,Protocol ${url.Scheme.ToUpper()}/{protocolVersion.Major}.{protocolVersion.Minor}};var pathBase pathbases.First(it absolutePath.StartsWith(it, StringComparison.OrdinalIgnoreCase));requestFeature.Path absolutePath[pathBase.Length..];requestFeature.PathBase pathBase;return requestFeature;}public Task StopAsync( CancellationToken cancellationToken){_listener.Stop();return Task.CompletedTask;}
}在调用Start方法将HttpListener启动后StartAsyncTContext方法开始“请求接收处理”循环。接收到的请求上下文被封装成HttpListenerContext上下文其承载的请求信息利用CreateRequestFeature方法转移到创建的HttpRequestFeature特性上。StartAsyncTContext方法创建的“空”HttpResponseFeature对象来描述响应另一个描述响应主体的StreamBodyFeature特性则根据创建的MemoryStream对象构建而成意味着中间件管道写入的响应主体的内容将暂存到这个内存流中。我们将这三个特性注册到创建的FeatureCollection集合上并将后者作为参数调用了IHttpApplicationTContext对象的CreateContext方法将TContext上下文创建出来。此上下文进一步作为参数调用了IHttpApplicationTContext对象的ProcessRequestAsync方法中间件管道得以接管请求。待中间件管道的处理工作完成后响应的内容还暂存在两个特性中我们还需要将它们应用到代表原始HttpListenerContext上下文上。StartAsyncTContext方法从HttpResponseFeature特性提取出响应状态码和响应报头转移到HttpListenerContext上下文上然后上述这个MemoryStream对象“拷贝”到HttpListenerContext上下文承载的响应主体输出流中。using App;
using Microsoft.AspNetCore.Hosting.Server;
using Microsoft.Extensions.DependencyInjection.Extensions;var builder WebApplication.CreateBuilder(args);
builder.Services.Replace(ServiceDescriptor.SingletonIServer, HttpListenerServer());
var app builder.Build();
app.Run(context context.Response.WriteAsync(Hello World!));
app.Run(http://localhost:5000/foobar/);我们采用上面的演示程序来检测HttpListenerServer能否正常工作。我们为HttpListenerServer类型创建了一个ServiceDescriptor对象将现有的服务器的服务注册替换掉。在调用WebApplication对象的Run方法时显式指定了具有PathBase“/foobar”的监听地址“http://localhost:5000/foobar/”如图1所示的浏览器以此地址访问应用会得到我们希望的结果。图1 HttpListenerServer返回的结果
