08-005 Hosting 之 HostingEngine : IHostingEngine

接口代码：

  public interface IHostingEngine
    {
        IDisposable Start(HostingContext context);
    }

 核心方法：

   public IDisposable Start(HostingContext context)
        {
			//  context.Builder = _builderFactory.CreateBuilder();
			EnsureBuilder(context);
			//   context.ServerFactory = _serverManager.GetServerFactory(context.ServerName);
			EnsureServerFactory(context);
			//    context.Server = context.ServerFactory.Initialize(context.Configuration);
			//    context.Builder.Server = context.Server;
			InitalizeServerFactory(context);
			/*
			    context.ApplicationStartup = _startupManager.LoadStartup(
                context.ApplicationName,
                context.EnvironmentName);

			 context.ApplicationStartup.Invoke(context.Builder); -- 这里才调用两个核心方法
             context.ApplicationDelegate = context.Builder.Build(); --生成RequestDelegate方法 
			  用来处理 HttpContext
	       */
			EnsureApplicationDelegate(context);

            var applicationLifetime = (ApplicationLifetime)context.Services.GetRequiredService<IApplicationLifetime>();
			// 创建 HttpContext 并进行执行
            var pipeline = new PipelineInstance(_httpContextFactory, context.ApplicationDelegate, _contextAccessor);
			/*
			 Start(IServerInformation serverInformation, Func<object, Task> application)
			 请求信息环境等信息 封装为Object  到 实现 IServerFactory 的用户自定义类；

			用户自定义类 调用 假定有此方法：  Task Invoke( 包含请求环境信息的Object );
			然后调用  PipelineInstance.Invoke  serverEnvironment 处理后为 HttpContext 
			继续调用  context.ApplicationDelegate = context.Builder.Build() 方法处理 HttpContext
			 PipelineInstance.Invoke 代码如下：
		    public Task Invoke(object serverEnvironment)
           {
            var httpContext = _httpContextFactory.CreateHttpContext(serverEnvironment);
            _contextAccessor.Value = httpContext;
            return _requestDelegate(httpContext);
           }

           */
		    // 这里简单理解为 服务启动了 比如启动IIS  具体怎么做要看服务是怎么实现了 
			var server = context.ServerFactory.Start(context.Server, pipeline.Invoke);

           
            return new Disposable(() =>
            {
                applicationLifetime.SignalStopping();
                server.Dispose();
                pipeline.Dispose();
                applicationLifetime.SignalStopped();
            });
        }