本系列将分析ASP.NET Core运行原理
本节将分析WebHost.CreateDefaultBuilder(args).UseStartup<Startup>().Build();
代码。
源代码参考.NET Core 2.0.0
该方法为WebHost类的静态方法,内部创建1个WebHostBuilder。
public static IWebHostBuilder CreateDefaultBuilder(string[] args) { var builder = new WebHostBuilder() .UseKestrel() .UseContentRoot(Directory.GetCurrentDirectory()) .ConfigureAppConfiguration((hostingContext, config) => { var env = hostingContext.HostingEnvironment; config.AddJsonFile("appsettings.json", optional: true, reloadOnChange: true) .AddJsonFile($"appsettings.{env.EnvironmentName}.json", optional: true, reloadOnChange: true); if (env.IsDevelopment()) { var appAssembly = Assembly.Load(new AssemblyName(env.ApplicationName)); if (appAssembly != null) { config.AddUserSecrets(appAssembly, optional: true); } } config.AddEnvironmentVariables(); if (args != null) { config.AddCommandLine(args); } }) .ConfigureLogging((hostingContext, logging) => { logging.AddConfiguration(hostingContext.Configuration.GetSection("Logging")); logging.AddConsole(); logging.AddDebug(); }) .UseIISIntegration() .UseDefaultServiceProvider((context, options) => { options.ValidateScopes = context.HostingEnvironment.IsDevelopment(); }); return builder; }
在UseKestrel()
方法中,注册了3个服务到List<Action<WebHostBuilderContext, IServiceCollection>>
字段上。(以供后续注册)
public static IWebHostBuilder UseKestrel(this IWebHostBuilder hostBuilder) { return hostBuilder.ConfigureServices((Action<IServiceCollection>) (services => { services.AddSingleton<ITransportFactory, LibuvTransportFactory>(); services.AddTransient<IConfigureOptions<KestrelServerOptions>, KestrelServerOptionsSetup>(); services.AddSingleton<IServer, KestrelServer>(); })); } public IWebHostBuilder ConfigureServices(Action<WebHostBuilderContext, IServiceCollection> configureServices) { this._configureServicesDelegates.Add((_, services) => configureServices(services)); return (IWebHostBuilder) this; }
UseContentRoot方法则是添加到IConfiguration字段上,这个字段在构造函数初始化this._config = (IConfiguration) new ConfigurationBuilder().AddEnvironmentVariables("ASPNETCORE_").Build();
public static IWebHostBuilder UseContentRoot(this IWebHostBuilder hostBuilder, string contentRoot) { if (contentRoot == null) throw new ArgumentNullException(nameof (contentRoot)); return hostBuilder.UseSetting(WebHostDefaults.ContentRootKey, contentRoot); } public IWebHostBuilder UseSetting(string key, string value) { this._config[key] = value; return (IWebHostBuilder) this; }
ConfigureAppConfiguration方法是添加到List<Action<WebHostBuilderContext, IConfigurationBuilder>>
字段上
在外部添加了AddJsonFile("appsettings.json")
、AddJsonFile(string.Format("appsettings.{0}.json", (object) hostingEnvironment.EnvironmentName))
AddEnvironmentVariables()
AddCommandLine(args)
public IWebHostBuilder ConfigureAppConfiguration(Action<WebHostBuilderContext, IConfigurationBuilder> configureDelegate) { this._configureAppConfigurationBuilderDelegates.Add(configureDelegate); return (IWebHostBuilder) this; }
ConfigureLogging注册Log到ServiceCollection上
在外部添加了3个ILoggerProviderlogging.AddConfiguration(hostingContext.Configuration.GetSection("Logging"));
logging.AddConsole();
logging.AddDebug();
public static IWebHostBuilder ConfigureLogging(this IWebHostBuilder hostBuilder, Action<WebHostBuilderContext, ILoggingBuilder> configureLogging) { return hostBuilder.ConfigureServices((context, services) => services.AddLogging(builder => configureLogging(context, builder)); } public IWebHostBuilder ConfigureServices(Action<WebHostBuilderContext, IServiceCollection> configureServices) { this._configureServicesDelegates.Add(configureServices); return (IWebHostBuilder) this; }
UseDefaultServiceProvider配置和替换服务
var options = new ServiceProviderOptions { ValidateScopes = context.HostingEnvironment.IsDevelopment()}; services.Replace(ServiceDescriptor.Singleton<IServiceProviderFactory<IServiceCollection>>((IServiceProviderFactory<IServiceCollection>) new DefaultServiceProviderFactory(options)));
UseStartup相当于注册了一个IStartup服务。
public static IWebHostBuilder UseStartup(this IWebHostBuilder hostBuilder, Type startupType) { string name = startupType.GetTypeInfo().Assembly.GetName().Name; return hostBuilder.UseSetting(WebHostDefaults.ApplicationKey, name).ConfigureServices((Action<IServiceCollection>) (services => { if (typeof (IStartup).GetTypeInfo().IsAssignableFrom(startupType.GetTypeInfo())) ServiceCollectionServiceExtensions.AddSingleton(services, typeof (IStartup), startupType); else ServiceCollectionServiceExtensions.AddSingleton(services, typeof (IStartup), (Func<IServiceProvider, object>) (sp => { IHostingEnvironment requiredService = sp.GetRequiredService<IHostingEnvironment>(); return (object) new ConventionBasedStartup(StartupLoader.LoadMethods(sp, startupType, requiredService.EnvironmentName)); })); })); }
根据Startup是否继承IStartup,来决定注册的方式。未继承的时候,会使用ConventionBasedStartup
来封装自定义的Startup。
Build方法是WebHostBuilder最终的目的,将构造一个WebHost返回。
同时初始化WebHost对象,WebHostBuilder.Build代码:
public IWebHost Build() { var hostingServices = BuildCommonServices(out var hostingStartupErrors); var applicationServices = hostingServices.Clone(); var hostingServiceProvider = hostingServices.BuildServiceProvider(); AddApplicationServices(applicationServices, hostingServiceProvider); var host = new WebHost( applicationServices, hostingServiceProvider, _options, _config, hostingStartupErrors); host.Initialize(); return host; }
在Build方法中,BuildCommonServices最为重要,将构造第一个ServiceCollection。这里我们称为hostingServices
。
将包含hostEnv、Config、ApplicationBuilder、Logging、StartupFilter、Startup、Server。参考BuildCommonServices
private IServiceCollection BuildCommonServices(out AggregateException hostingStartupErrors) { if (!this._options.PreventHostingStartup) { foreach (string hostingStartupAssembly in (IEnumerable<string>) this._options.HostingStartupAssemblies) { foreach (HostingStartupAttribute customAttribute in Assembly.Load(new AssemblyName(hostingStartupAssembly)).GetCustomAttributes<HostingStartupAttribute>()) ((IHostingStartup) Activator.CreateInstance(customAttribute.HostingStartupType)).Configure((IWebHostBuilder) this); } } ServiceCollection services = new ServiceCollection(); // hostEnv _hostingEnvironment.Initialize(this._options.ApplicationName, this.ResolveContentRootPath(this._options.ContentRootPath, AppContext.BaseDirectory), this._options); services.AddSingleton<IHostingEnvironment>(this._hostingEnvironment); // config IConfigurationBuilder configurationBuilder = new ConfigurationBuilder().SetBasePath(this._hostingEnvironment.ContentRootPath).AddInMemoryCollection(this._config.AsEnumerable()); foreach (Action<WebHostBuilderContext, IConfigurationBuilder> configurationBuilderDelegate in this._configureAppConfigurationBuilderDelegates) configurationBuilderDelegate(this._context, configurationBuilder); IConfigurationRoot configurationRoot = configurationBuilder.Build(); services.AddSingleton<IConfiguration>((IConfiguration) configurationRoot); services.AddOptions(); // application services.AddTransient<IApplicationBuilderFactory, ApplicationBuilderFactory>(); services.AddTransient<IHttpContextFactory, HttpContextFactory>(); services.AddScoped<IMiddlewareFactory, MiddlewareFactory>(); // log services.AddLogging(); services.AddTransient<IStartupFilter, AutoRequestServicesStartupFilter>(); services.AddTransient<IServiceProviderFactory<IServiceCollection>, DefaultServiceProviderFactory>(); // 配置的StartupType if (!string.IsNullOrEmpty(this._options.StartupAssembly)) { Type startupType = StartupLoader.FindStartupType(this._options.StartupAssembly, this._hostingEnvironment.EnvironmentName); if (typeof (IStartup).GetTypeInfo().IsAssignableFrom(startupType.GetTypeInfo())) ServiceCollectionServiceExtensions.AddSingleton(services, typeof (IStartup), startupType); else ServiceCollectionServiceExtensions.AddSingleton(services, typeof (IStartup), new ConventionBasedStartup(StartupLoader.LoadMethods(startupType))); } // UseStartup、UseKestrel、ConfigureLogging foreach (Action<WebHostBuilderContext, IServiceCollection> servicesDelegate in this._configureServicesDelegates) servicesDelegate(this._context, (IServiceCollection) services); return (IServiceCollection) services; }
当 hostingServices
创建完成后,会马上拷贝一份applicationServices
提供给WebHost使用,同时创建第一个ServiceProvider hostingServiceProvider
。
host.Initialize()该方法则是初始化WebHost
_applicationServices
(微软的内部字段命名,感觉不太规范);RequestDelegate
。public void Initialize() { _startup = _hostingServiceProvider.GetService<IStartup>(); _applicationServices = _startup.ConfigureServices(_applicationServiceCollection); EnsureServer(); var builderFactory = _applicationServices.GetRequiredService<IApplicationBuilderFactory>(); var builder = builderFactory.CreateBuilder(Server.Features); builder.ApplicationServices = _applicationServices; var startupFilters = _applicationServices.GetService<IEnumerable<IStartupFilter>>(); Action<IApplicationBuilder> configure = _startup.Configure; foreach (var filter in startupFilters.Reverse()) { configure = filter.Configure(configure); } configure(builder); this._application = builder.Build(); // RequestDelegate }
创建完 WebHost 之后,便调用它的 Run 方法,而 Run 方法会去调用 WebHost 的 StartAsync 方法
public static void Run(this IWebHost host) { host.RunAsync(cts.Token, "Application started. Press Ctrl+C to shut down.").GetAwaiter().GetResult(); } private static async Task RunAsync(this IWebHost host, CancellationToken token, string shutdownMessage) { await host.StartAsync(token); var hostingEnvironment = host.Services.GetService<IHostingEnvironment>(); Console.WriteLine($"Hosting environment: {hostingEnvironment.EnvironmentName}"); Console.WriteLine($"Content root path: {hostingEnvironment.ContentRootPath}"); var serverAddresses = host.ServerFeatures.Get<IServerAddressesFeature>()?.Addresses; if (serverAddresses != null) foreach (var address in serverAddresses) Console.WriteLine($"Now listening on: {address}"); if (!string.IsNullOrEmpty(shutdownMessage)) Console.WriteLine(shutdownMessage); } public virtual async Task StartAsync(CancellationToken cancellationToken = default (CancellationToken)) { Initialize(); _applicationLifetime = _applicationServices.GetRequiredService<IApplicationLifetime>() as ApplicationLifetime; _hostedServiceExecutor = _applicationServices.GetRequiredService<HostedServiceExecutor>(); var httpContextFactory = _applicationServices.GetRequiredService<IHttpContextFactory>(); var hostingApp = new HostingApplication(_application, _logger, diagnosticSource, httpContextFactory); await Server.StartAsync(hostingApp, cancellationToken).ConfigureAwait(false); _applicationLifetime?.NotifyStarted(); await _hostedServiceExecutor.StartAsync(cancellationToken).ConfigureAwait(false); }
hostingServices
(WebHostBuilder) 和 _applicationServices
(WebHost)。区别是_applicationServices中比hostingServices多处Startup方法注册的服务。_applicationServices
生成前,Configure在_applicationServices
生成后。UseKestrel
,使用在WebHost的Run
方法new WebHostBuilder() .UseKestrel() // 使用Kestrel服务器 .UseContentRoot(Directory.GetCurrentDirectory()) // 配置根目录 会在ConfigurationBuilder、 IHostingEnvironment(后续其他中间件) 和 WebHostOptions(WebHost)用到。 .ConfigureAppConfiguration((context, builder) => builder.AddJsonFile("appsetting.json", true, true)) // 添加配置源 .ConfigureLogging(builder => builder.AddConsole()) // 添加日志适配器 .UseStartup<Startup>() // 选择Startup .Build().Run(); // 生成WebHost 并 启动
本文链接:http://neverc.cnblogs.com/p/7988226.html