前一篇提到WebHost.CreateDefaultBuilder(args)方法创建了WebHostBuilder实例,WebHostBuilder实例有三个主要功能 1、构建了IConfiguration实例和基础环境配置,2、构建了IServiceCollection服务,也就是依赖注入的容器,3、创建了webhost实例,这个webhost就是我们的接收请求的第一个管道,其中暴露出来的主要方法Build,请看源代码:
1 public IWebHost Build() 2 { 3 if (!_webHostBuilt) 4 { 5 _webHostBuilt = true; 6 AggregateException hostingStartupErrors; 7 IServiceCollection serviceCollection = BuildCommonServices(out hostingStartupErrors); 8 IServiceCollection serviceCollection2 = serviceCollection.Clone(); 9 IServiceProvider hostingServiceProvider = _003CBuild_003Eg__GetProviderFromFactory_007C13_0(serviceCollection); 10 if (!_options.SuppressstatusMessages) 11 { 12 if (Environment.GetEnvironmentvariable("Hosting:Environment") != null) 13 { 14 Console.WriteLine("The environment variable ‘Hosting:Environment‘ is obsolete and has been replaced with ‘ASPNETCORE_ENVIRONMENT‘"); 15 } 16 if (Environment.GetEnvironmentvariable("ASPNET_ENV") != null) 17 { 18 Console.WriteLine("The environment variable ‘ASPNET_ENV‘ is obsolete and has been replaced with ‘ASPNETCORE_ENVIRONMENT‘"); 19 } 20 if (Environment.GetEnvironmentvariable("ASPNETCORE_SERVER.URLS") != null) 21 { 22 Console.WriteLine("The environment variable ‘ASPNETCORE_SERVER.URLS‘ is obsolete and has been replaced with ‘ASPNETCORE_URLS‘"); 23 } 24 } 25 Addapplicationservices(serviceCollection2,hostingServiceProvider); 26 WebHost webHost = new WebHost(serviceCollection2,hostingServiceProvider,_options,_config,hostingStartupErrors); 27 try 28 { 29 webHost.Initialize(); 30 ILogger<WebHost> requiredService = webHost.Services.GetrequiredService<ILogger<WebHost>>(); 31 foreach (IGrouping<string,string> item in from g in _options.GetFinalHostingStartupAssemblies().GroupBy((string a) => a,StringComparer.OrdinalIgnoreCase) 32 where g.Count() > 1 33 select g) 34 { 35 requiredService.LogWarning($"The assembly {item} was specified multiple times. Hosting startup assemblies should only be specified once."); 36 } 37 return webHost; 38 } 39 catch 40 { 41 webHost.dispose(); 42 throw; 43 } 44 } 45 throw new InvalidOperationException(Resources.WebHostBuilder_SingleInstance); 46 }
调用BuildCommonServices私有方法主要是注入一些程序所需的基础组件,请看源代码:
1 private IServiceCollection BuildCommonServices(out AggregateException hostingStartupErrors) 2 { 3 hostingStartupErrors = null; 4 _options = new WebHostOptions(_config,Assembly.GetEntryAssembly()?.GetName().Name); 5 if (!_options.PreventHostingStartup) 6 { 7 List<Exception> list = new List<Exception>(); 8 foreach (string item in _options.GetFinalHostingStartupAssemblies().distinct(StringComparer.OrdinalIgnoreCase)) 9 { 10 try 11 { 12 foreach (HostingStartupAttribute customAttribute in Assembly.Load(new AssemblyName(item)).GetCustomAttributes<HostingStartupAttribute>()) 13 { 14 ((IHostingStartup)Activator.CreateInstance(customAttribute.HostingStartupType)).Configure(this); 15 } 16 } 17 catch (Exception innerException) 18 { 19 list.Add(new InvalidOperationException("Startup assembly " + item + " Failed to execute. See the inner exception for more details.",innerException)); 20 } 21 } 22 if (list.Count > 0) 23 { 24 hostingStartupErrors = new AggregateException(list); 25 } 26 } 27 string contentRootPath = ResolveContentRootPath(_options.ContentRootPath,AppContext.BaseDirectory); 28 _hostingEnvironment.Initialize(contentRootPath,_options); 29 _context.HostingEnvironment = _hostingEnvironment; 30 ServiceCollection serviceCollection = new ServiceCollection(); 31 serviceCollection.AddSingleton(_options); 32 ((IServiceCollection)serviceCollection).AddSingleton((IHostingEnvironment)_hostingEnvironment); 33 ((IServiceCollection)serviceCollection).AddSingleton((Microsoft.Extensions.Hosting.IHostingEnvironment)_hostingEnvironment); 34 serviceCollection.AddSingleton(_context); 35 IConfigurationBuilder configurationBuilder = new ConfigurationBuilder().SetBasePath(_hostingEnvironment.ContentRootPath).AddConfiguration(_config); 36 foreach (Action<WebHostBuilderContext,IConfigurationBuilder> configureAppConfigurationBuilderDelegate in _configureAppConfigurationBuilderDelegates) 37 { 38 configureAppConfigurationBuilderDelegate(_context,configurationBuilder); 39 } 40 IConfigurationRoot configurationRoot = configurationBuilder.Build(); 41 ((IServiceCollection)serviceCollection).AddSingleton((IConfiguration)configurationRoot); 42 _context.Configuration = configurationRoot; 43 DiagnosticListener implementationInstance = new DiagnosticListener("Microsoft.AspNetCore"); 44 serviceCollection.AddSingleton(implementationInstance); 45 ((IServiceCollection)serviceCollection).AddSingleton((DiagnosticSource)implementationInstance); 46 serviceCollection.AddTransient<IApplicationBuilderFactory,ApplicationBuilderFactory>(); 47 serviceCollection.AddTransient<IHttpContextFactory,HttpContextFactory>(); 48 serviceCollection.AddScoped<IMiddlewareFactory,MiddlewareFactory>(); 49 serviceCollection.AddOptions(); 50 serviceCollection.AddLogging(); 51 serviceCollection.AddTransient<IStartupFilter,AutoRequestServicesstartupFilter>(); 52 serviceCollection.AddTransient<IServiceProviderFactory<IServiceCollection>,DefaultServiceProviderFactory>(); 53 serviceCollection.AddSingleton<ObjectPoolProvider,DefaultObjectPoolProvider>(); 54 if (!string.IsNullOrEmpty(_options.StartupAssembly)) 55 { 56 try 57 { 58 Type startupType = StartupLoader.FindStartupType(_options.StartupAssembly,_hostingEnvironment.EnvironmentName); 59 if (IntrospectionExtensions.GetTypeInfo(typeof(IStartup)).IsAssignableFrom(startupType.GetTypeInfo())) 60 { 61 serviceCollection.AddSingleton(typeof(IStartup),startupType); 62 } 63 else 64 { 65 serviceCollection.AddSingleton(typeof(IStartup),delegate (IServiceProvider sp) 66 { 67 IHostingEnvironment requiredService = sp.GetrequiredService<IHostingEnvironment>(); 68 return new ConventionBasedStartup(StartupLoader.LoadMethods(sp,startupType,requiredService.EnvironmentName)); 69 }); 70 } 71 } 72 catch (Exception source) 73 { 74 ExceptiondispatchInfo capture = ExceptiondispatchInfo.Capture(source); 75 ((IServiceCollection)serviceCollection).AddSingleton((Func<IServiceProvider,IStartup>)delegate 76 { 77 capture.Throw(); 78 return null; 79 }); 80 } 81 } 82 foreach (Action<WebHostBuilderContext,IServiceCollection> configureServicesDelegate in _configureServicesDelegates) 83 { 84 configureServicesDelegate(_context,serviceCollection); 85 } 86 return serviceCollection; 87 }
这个方法中其中就包含了注入IConfiguration的代码和构建IServiceCollection容器的代码,当然还有一些其他的主要中间件注入啊IApplicationBuilderFactory,包括HttpContextFactory等等都在这个方法里面被IServiceCollection容器管理,具体请看下图
这里讲清楚之后,我们直接进入UseStartup方法中,这个方法是注入了Startup的实例,请看主要源代码
1 public static IWebHostBuilder UseStartup(this IWebHostBuilder hostBuilder,Type startupType) 2 { 3 string name = startupType.GetTypeInfo().Assembly.GetName().Name; 4 return hostBuilder.UseSetting(WebHostDefaults.ApplicationKey,name).ConfigureServices(delegate (IServiceCollection services) 5 { 6 if (IntrospectionExtensions.GetTypeInfo(typeof(IStartup)).IsAssignableFrom(startupType.GetTypeInfo())) 7 { 8 services.AddSingleton(typeof(IStartup),startupType); 9 } 10 else 11 { 12 services.AddSingleton(typeof(IStartup),delegate (IServiceProvider sp) 13 { 14 IHostingEnvironment requiredService = sp.GetrequiredService<IHostingEnvironment>(); 15 return new ConventionBasedStartup(StartupLoader.LoadMethods(sp,requiredService.EnvironmentName)); 16 }); 17 } 18 }); 19 }
上面只是被IServiceCollection所管理 并没有真正起作用,真正调用的是Main方法中的Build().Run(),这里的Build就是上面那个IWebHostBuilder中的主要的构建方法,而Run则是正式启动应用程序和调用Startup中的ConfigureServices方法
请看代码:
分享Program类的过程大致就到这里了
原文地址:https://www.jb51.cc/netcore/670851.html
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