ASP.NET Core启动流程

ASP.NET Core启动流程

new WebHostBuilder()

初始化类型WebHostBuilder的属性

IServer _server

List<Action> _configures

UseHttpListener()

这是IWebHostBuilder下面的一个扩展方法

UseServer(new HttpListenerServer(urls))

• new HttpListenerServer(urls)

  • HttpListener _httpListener

  • string[] _urls

    httpServer要监听的请求地址

• UseServer(new HttpListenerServer(urls))

  • 给IServer _server赋值，值为HttpListenerServer实例

• return IWebHostBuilder

Configure(app => app.Use())

配置应用程序，中间件

给List<Action> _configures赋值，值为Action

return IWebHostBuilder

Build()

new ApplicationBuilder()

• 初始化List<Func<RequestDelegate, RequestDelegate>> _middlewares

遍历List<Action> _configures

• 赋值为空的ApplicationBuilder()

return new WebHost(_server, builder.Build())

参数分别为HTTPServer，(new ApplicationBuilder()).Build()

• builder.Build()

  • _middlewares.Reverse()

    反转所有的中间件

  • return httpContext =>{… };

    构建中间件

    • RequestDelegate next = _ => { _.Response.StatusCode = 404; return Task.CompletedTask; };

      定义请求处理失败的中间件（委托）

    • foreach (var middleware in _middlewares)
      {
      next = middleware(next);
      }

      将所有的中间件处理成委托链表

    • return next(httpContext);

      返回请求的处理委托链表

StartAsync()

_server.StartAsync(_handler)

• Array.ForEach(_urls, url => _httpListener.Prefixes.Add(url));

  将需要监听的http地址赋值给HTTPServer

• _httpListener.Start();

  启动HTTPServer

• while (true){…}

  监听HTTP请求

  • var listenerContext = await _httpListener.GetContextAsync();

    服务器生成HTTP请求原始上下文，包括原始request和response

  • var feature = new HttpListenerFeature(listenerContext);

    根据原始上下文生成HttpServerFeature，包括IHttpRequestFeature, IHttpResponseFeature

  • var features = new FeatureCollection()
    .Set(feature)
    .Set(feature);

    生成（初始化）FeatureCollection（值为k-v形式）
    分别设置key为IHttpRequestFeature，IHttpResponseFeature，value都是feature

  • var httpContext = new HttpContext(features);

    生成（初始化）ASP.NET Core的http请求上下文，包括HttpRequest，HttpResponse

  • await handler(httpContext);

    请求处理

  • listenerContext.Response.Close();

    发送响应到客户端，请求结束