.Net Core后端架构实战【2-实现动态路由与Dynamic API】

摘要：基于.NET Core 7.0WebApi后端架构实战【2-实现动态路由与Dynamic API】  2023/02/22, ASP.NET Core 7.0, VS2022

引言

    使用过ABP vNext和Furion框架的可能都会对它们的动态API感到好奇，不用手动的去定义，它会动态的去创建API控制器。后端代码
架构的复杂在核心代码，如果这些能封装的好提升的是小组整体的生产力。灵图图书的扉页都会有这样一句话："站在巨人的肩膀上"。我在
这里大言不惭的说上一句我希望我也能成为"巨人"！

动态路由

在.Net Core WebAPI程序中通过可全局或局部修改的自定义Route属性和URL映射组件匹配传入的HTTP请求替代默认路由即为动态路由

WebApplicationBuilder

在3.1以及5.0的版本中，Configure方法中会自动添加UseRouting()与UseEndpoints()方法，但是在6.0以上版本已经没有了。其实在创建WebApplicationBuilder实例的时候默认已经添加进去了。请看源码：

var builder = WebApplication.CreateBuilder(args);

/// <summary>
/// Initializes a new instance of the class with preconfigured defaults.
/// </summary>
/// <param name="args">Command line arguments</param>
/// <returns>The <see cref="WebApplicationBuilder"/>.</returns>
public static WebApplicationBuilder CreateBuilder(string[] args) =>
    new(new WebApplicationOptions() { Args = args });

internal WebApplicationBuilder(WebApplicationOptions options, Action? configureDefaults = null)
{
    Services = _services;
    var args = options.Args;
    // Run methods to configure both generic and web host defaults early to populate config from appsettings.json
    // environment variables (both DOTNET_ and ASPNETCORE_ prefixed) and other possible default sources to prepopulate
    // the correct defaults.
    _bootstrapHostBuilder = new BootstrapHostBuilder(Services, _hostBuilder.Properties);
    // Don't specify the args here since we want to apply them later so that args
    // can override the defaults specified by ConfigureWebHostDefaults
    _bootstrapHostBuilder.ConfigureDefaults(args: null);
    // This is for testing purposes
    configureDefaults?.Invoke(_bootstrapHostBuilder);
    // We specify the command line here last since we skipped the one in the call to ConfigureDefaults.
    // The args can contain both host and application settings so we want to make sure
    // we order those configuration providers appropriately without duplicating them
    if (args is { Length: > 0 })
    {
        _bootstrapHostBuilder.ConfigureAppConfiguration(config =>
        {
            config.AddCommandLine(args);
        });
    }
    _bootstrapHostBuilder.ConfigureWebHostDefaults(webHostBuilder =>
    {
        // Runs inline.
        //看这里
        webHostBuilder.Configure(ConfigureApplication);
        // Attempt to set the application name from options
        options.ApplyApplicationName(webHostBuilder);
    });
    // Apply the args to host configuration last since ConfigureWebHostDefaults overrides a host specific setting (the application n
    _bootstrapHostBuilder.ConfigureHostConfiguration(config =>
    {
        if (args is { Length: > 0 })
        {
            config.AddCommandLine(args);
        }
        // Apply the options after the args
        options.ApplyHostConfiguration(config);
    });
    Configuration = new();
    // This is chained as the first configuration source in Configuration so host config can be added later without overriding app c
    Configuration.AddConfiguration(_hostConfigurationManager);
    // Collect the hosted services separately since we want those to run after the user's hosted services
    _services.TrackHostedServices = true;
    // This is the application configuration
    var (hostContext, hostConfiguration) = _bootstrapHostBuilder.RunDefaultCallbacks(Configuration, _hostBuilder);
    // Stop tracking here
    _services.TrackHostedServices = false;
    // Capture the host configuration values here. We capture the values so that
    // changes to the host configuration have no effect on the final application. The
    // host configuration is immutable at this point.
    _hostConfigurationValues = new(hostConfiguration.AsEnumerable());
    // Grab the WebHostBuilderContext from the property bag to use in the ConfigureWebHostBuilder
    var webHostContext = (WebHostBuilderContext)hostContext.Properties[typeof(WebHostBuilderContext)];
    // Grab the IWebHostEnvironment from the webHostContext. This also matches the instance in the IServiceCollection.
    Environment = webHostContext.HostingEnvironment;
    Logging = new LoggingBuilder(Services);
    Host = new ConfigureHostBuilder(hostContext, Configuration, Services);
    WebHost = new ConfigureWebHostBuilder(webHostContext, Configuration, Services);
    Services.AddSingleton(_ => Configuration);
}

private void ConfigureApplication(WebHostBuilderContext context, IApplicationBuilder app)
{
    Debug.Assert(_builtApplication is not null);
    // UseRouting called before WebApplication such as in a StartupFilter
    // lets remove the property and reset it at the end so we don't mess with the routes in the filter
    if (app.Properties.TryGetValue(EndpointRouteBuilderKey, out var priorRouteBuilder))
    {
        app.Properties.Remove(EndpointRouteBuilderKey);
    }
    if (context.HostingEnvironment.IsDevelopment())
    {
        app.UseDeveloperExceptionPage();
    }
    // Wrap the entire destination pipeline in UseRouting() and UseEndpoints(), essentially:
    // destination.UseRouting()
    // destination.Run(source)
    // destination.UseEndpoints()
    // Set the route builder so that UseRouting will use the WebApplication as the IEndpointRouteBuilder for route matching
    app.Properties.Add(WebApplication.GlobalEndpointRouteBuilderKey, _builtApplication);
    // Only call UseRouting() if there are endpoints configured and UseRouting() wasn't called on the global route builder already
    if (_builtApplication.DataSources.Count > 0)
    {
        // If this is set, someone called UseRouting() when a global route builder was already set
        if (!_builtApplication.Properties.TryGetValue(EndpointRouteBuilderKey, out var localRouteBuilder))
        {
            //添加路由中间件
            app.UseRouting();
        }
        else
        {
            // UseEndpoints will be looking for the RouteBuilder so make sure it's set
            app.Properties[EndpointRouteBuilderKey] = localRouteBuilder;
        }
    }
    // Wire the source pipeline to run in the destination pipeline
    app.Use(next =>
    {
        _builtApplication.Run(next);
        return _builtApplication.BuildRequestDelegate();
    });
    if (_builtApplication.DataSources.Count > 0)
    {
        // We don't know if user code called UseEndpoints(), so we will call it just in case, UseEndpoints() will ignore duplicate DataSources
        //添加终结点中间件
        app.UseEndpoints(_ => { });
    }
    // Copy the properties to the destination app builder
    foreach (var item in _builtApplication.Properties)
    {
        app.Properties[item.Key] = item.Value;
    }
    // Remove the route builder to clean up the properties, we're done adding routes to the pipeline
    app.Properties.Remove(WebApplication.GlobalEndpointRouteBuilderKey);
    // reset route builder if it existed, this is needed for StartupFilters
    if (priorRouteBuilder is not null)
    {
        app.Properties[EndpointRouteBuilderKey] = priorRouteBuilder;
    }
}

public IWebHostBuilder Configure(Action<WebHostBuilderContext, IApplicationBuilder> configure)
{
    var startupAssemblyName = configure.GetMethodInfo().DeclaringType!.Assembly.GetName().Name!;
    UseSetting(WebHostDefaults.ApplicationKey, startupAssemblyName);
    // Clear the startup type
    _startupObject = configure;
    _builder.ConfigureServices((context, services) =>
    {
        if (object.ReferenceEquals(_startupObject, configure))
        {
            services.Configure(options =>
            {
                var webhostBuilderContext = GetWebHostBuilderContext(context);
                options.ConfigureApplication = app => configure(webhostBuilderContext, app);
            });
        }
    });
    return this;
}

private static WebHostBuilderContext GetWebHostBuilderContext(HostBuilderContext context)
{
    if (!context.Properties.TryGetValue(typeof(WebHostBuilderContext), out var contextVal))
    {
        var options = new WebHostOptions(context.Configuration, Assembly.GetEntryAssembly()?.GetName().Name ?? string.Empty);
        var webHostBuilderContext = new WebHostBuilderContext
        {
            Configuration = context.Configuration,
            HostingEnvironment = new HostingEnvironment(),
        };
        webHostBuilderContext.HostingEnvironment.Initialize(context.HostingEnvironment.ContentRootPath, options);
        context.Properties[typeof(WebHostBuilderContext)] = webHostBuilderContext;
        context.Properties[typeof(WebHostOptions)] = options;
        return webHostBuilderContext;
    }
    // Refresh config, it's periodically updated/replaced
    var webHostContext = (WebHostBuilderContext)contextVal;
    webHostContext.Configuration = context.Configuration;
    return webHostContext;
}

UseRouting

源码如下图所示：

①erifyRoutingServicesAreRegistered用于验证路由服务是否已注册到容器内部

②判断在请求管道的共享数据字典的Properties中是否有GlobalEndpointRouteBuilderKey的键，如果没有则New一个新的终结点路由构建者对象，并将EndpointRouteBuilder添加到共享字典中。后面UseEndpoints(Action<IEndpointRouteBuilder> configure)执行时，会将前面New的DefaultEndpointRouteBuilder 实例取出，并进一步配置它： configure(EndpointRouteBuilder实例)

③将EndpointRoutingMiddleware中间件注册到管道中，该中间件根据请求和Url匹配最佳的Endpoint,然后将该终结点交由EndpointMiddleware 处理。

UseEndpoints

源码如下图所示：

 ①VerifyEndpointRoutingMiddlewareIsRegistered方法将EndpointRouteBuilder从请求管道的共享字典中取出，如果没有则说明之前没有调用UseRouting()，所以调用UseEndpoints()之前要先调用UseRouting()，VerifyEndpointRoutingMiddlewareIsRegistered方法如下图所示：

②EndpointMiddleware主要是在EndpointRoutingMiddleware筛选出endpoint之后，调用该endpoint的endpoint.RequestDelegate(httpContext)进行请求处理。并且这个中间件会最终执行RequestDelegate委托来处理请求。请求的处理大部分功能在中间件EndpointRoutingMiddleware中，它有个重要的属性_endpointDataSource保存了上文中初始化阶段生成的MvcEndpointDataSource，而中间件EndpointMiddleware的功能比较简单，主要是在EndpointRoutingMiddleware筛选出endpoint之后，调用该endpoint.RequestDelegate(httpContext)方法进行请求处理。

看一下Endpoint类源码，Endpoint就是定义谁(Action)来执行请求的对象

public class Endpoint
{
    ///<summary>
    /// Creates a new instance of.
    ///</summary>
    ///<param name="requestDelegate">The delegate used to process requests for the endpoint.</param>
    ///<param name="metadata">
    /// The endpoint <see cref="EndpointMetadataCollection"/>. May be null.
    ///</param>
    ///<param name="displayName">
    /// The informational display name of the endpoint. May be null.
    /// </param>
    public Endpoint(
        RequestDelegate? requestDelegate,
        EndpointMetadataCollection? metadata,
        string? displayName)
    {
        // All are allowed to be null
        RequestDelegate = requestDelegate;
        Metadata = metadata ?? EndpointMetadataCollection.Empty;
        DisplayName = displayName;
    }
    /// <summary>
    /// Gets the informational display name of this endpoint.
    /// </summary>
    public string? DisplayName { get; }
    /// <summary>
    /// Gets the collection of metadata associated with this endpoint.
    /// 
    public EndpointMetadataCollection Metadata { get; }
    /// <summary>
    /// Gets the delegate used to process requests for the endpoint.
    /// </summary>
    public RequestDelegate? RequestDelegate { get; }
    /// <summary>
    /// Returns a string representation of the endpoint.
    /// </summary>
    public override string? ToString() => DisplayName ?? base.ToString();
}

Metadata非常重要，是存放控制器还有Action的元数据，在应用程序启动的时候就将控制器和Action的关键信息给存入，例如路由、特性、HttpMethod等

RequestDelegate 用于将请求(HttpContext)交给资源(Action)执行

AddControllers

我们来看下AddControllers()和AddMvcCore()及相关联的源码

MvcServiceCollectionExtensions文件中，AddControllersCore方法用于添加控制器的核心服务，它最主要的作用是主要作用就是扫描所有的有关程序集封装成ApplicationPart。

public static class MvcServiceCollectionExtensions
{
    /// <summary>
    /// Adds services for controllers to the specified. This method will not
    /// register services used for views or pages.
    /// </summary>
    ///<param name="services">The <see cref="IServiceCollection" /> to add services to.</param>
    /// <returns>An <see cref="IMvcBuilder"/> that can be used to further configure the MVC services.</returns>
    /// <remarks>
    /// <para>
    /// This method configures the MVC services for the commonly used features with controllers for an API. This
    /// combines the effects of <see cref="MvcCoreServiceCollectionExtensions.AddMvcCore(IServiceCollection)"/>,
    /// <see cref="MvcApiExplorerMvcCoreBuilderExtensions.AddApiExplorer(IMvcCoreBuilder)"/>,
    /// <see cref="MvcCoreMvcCoreBuilderExtensions.AddAuthorization(IMvcCoreBuilder)"/>,
    /// <see cref="MvcCorsMvcCoreBuilderExtensions.AddCors(IMvcCoreBuilder)"/>,
    /// <see cref="MvcDataAnnotationsMvcCoreBuilderExtensions.AddDataAnnotations(IMvcCoreBuilder)"/>,
    /// and <see cref="MvcCoreMvcCoreBuilderExtensions.AddFormatterMappings(IMvcCoreBuilder)"/>.
    /// </para>
    /// <para>
    /// To add services for controllers with views call <see cref="AddControllersWithViews(IServiceCollection)"/>
    /// on the resulting builder.
    /// </para>
    /// <para>
    /// To add services for pages call <see cref="AddRazorPages(IServiceCollection)"/>
    /// on the resulting builder.
    /// on the resulting builder.
    /// </remarks>
    public static IMvcBuilder AddControllers(this IServiceCollection services)
    {
        if (services == null)
        {
            throw new ArgumentNullException(nameof(services));
        }

        //添加Controllers核心服务
        var builder = AddControllersCore(services);
        return new MvcBuilder(builder.Services, builder.PartManager);
    }

    private static IMvcCoreBuilder AddControllersCore(IServiceCollection services)
    {
        // This method excludes all of the view-related services by default.
        var builder = services
            .AddMvcCore()//这个是核心，返回IMvcCoreBuilder对象，其后的服务引入都是基于它的
            .AddApiExplorer()
            .AddAuthorization()
            .AddCors()
            .AddDataAnnotations()
            .AddFormatterMappings();

        if (MetadataUpdater.IsSupported)
        {
            services.TryAddEnumerable(
                ServiceDescriptor.Singleton<IActionDescriptorChangeProvider, HotReloadService>());
        }

        return builder;
    }
}

AddMvcCore方法用于添加MVC的核心服务，下面的GetApplicationPartManager方法先获取ApplicationPartManager对象，然后将当前程序集封装成了ApplicationPart放进ApplicationParts集合中。
ConfigureDefaultFeatureProviders(partManager)主要作用是创建了一个新的ControllerFeatureProvider实例放进了partManager的FeatureProviders属性中，注意这个ControllerFeatureProvider对象在后面遍历ApplicationPart的时候负责找出里面的Controller。
AddMvcCore()方法其后是添加Routing服务再接着添加Mvc核心服务然后构建一个MvcCoreBuilder实例并返回

///<summary>
/// Extension methods for setting up essential MVC services in an.
///</summary>
public static class MvcCoreServiceCollectionExtensions
{
    ///<summary>
    /// Adds the minimum essential MVC services to the specified 
    /// <see cref="IServiceCollection" />. Additional services
    /// including MVC's support for authorization, formatters, and validation must be added separately 
    /// using the <see cref="IMvcCoreBuilder"/> returned from this method.
    ///</summary>
    ///<param name="services">The <see cref="IServiceCollection" /> to add services to.</param>
    /// <returns>
    /// An <see cref="IMvcCoreBuilder"/> that can be used to further configure the MVC services.
    /// </returns>
    /// <remarks>
    /// The <see cref="MvcCoreServiceCollectionExtensions.AddMvcCore(IServiceCollection)"/> 
    /// approach for configuring
    /// MVC is provided for experienced MVC developers who wish to have full control over the 
    /// set of default services
    /// registered. <see cref="MvcCoreServiceCollectionExtensions.AddMvcCore(IServiceCollection)"/> 
    /// will register
    /// the minimum set of services necessary to route requests and invoke controllers. 
    /// It is not expected that any
    /// application will satisfy its requirements with just a call to
    /// <see cref="MvcCoreServiceCollectionExtensions.AddMvcCore(IServiceCollection)"/>
    /// . Additional configuration using the
    /// <see cref="IMvcCoreBuilder"/> will be required.
    /// </remarks>
    public static IMvcCoreBuilder AddMvcCore(this IServiceCollection services)
    {
        if (services == null)
        {
            throw new ArgumentNullException(nameof(services));
        }
        //获取注入的IWebHostEnvironment环境对象
        var environment = GetServiceFromCollection(services);
        //获取程序中所有关联的程序集的ApplicationPartManager
        var partManager = GetApplicationPartManager(services, environment);
        services.TryAddSingleton(partManager);
        //给ApplicationPartManager添加ControllerFeature
        ConfigureDefaultFeatureProviders(partManager);
        //调用services.AddRouting();
        ConfigureDefaultServices(services);
        //添加MVC相关联的服务至IOC容器中
        AddMvcCoreServices(services);
        var builder = new MvcCoreBuilder(services, partManager);
        return builder;

    }

    private static ApplicationPartManager GetApplicationPartManager(IServiceCollection services, IWebHostEnvironment? environment)
    {
        var manager = GetServiceFromCollection(services);
        if (manager == null)
        {
            manager = new ApplicationPartManager();
            //获取当前主程序集的名称
            var entryAssemblyName = environment?.ApplicationName;
            if (string.IsNullOrEmpty(entryAssemblyName))
            {
                return manager;
            }
            //找出所有引用的程序集并将他们添加到ApplicationParts中
            manager.PopulateDefaultParts(entryAssemblyName);
        }

        return manager;
    }

    private static void ConfigureDefaultFeatureProviders(ApplicationPartManager manager)
    {
        if (!manager.FeatureProviders.OfType().Any())
        {
            manager.FeatureProviders.Add(new ControllerFeatureProvider());
        }
    }

    private static void ConfigureDefaultServices(IServiceCollection services)
    {
        services.AddRouting();
    }

    internal static void AddMvcCoreServices(IServiceCollection services)
    {
        //
        // Options
        //
        services.TryAddEnumerable(
            ServiceDescriptor.Transient<IConfigureOptions, MvcCoreMvcOptionsSetup>());
        services.TryAddEnumerable(
            ServiceDescriptor.Transient<IPostConfigureOptions, MvcCoreMvcOptionsSetup>());
        services.TryAddEnumerable(
            ServiceDescriptor.Transient<IConfigureOptions, ApiBehaviorOptionsSetup>());
        services.TryAddEnumerable(
            ServiceDescriptor.Transient<IConfigureOptions, MvcCoreRouteOptionsSetup>());

        //
        // Action Discovery
        //
        // These are consumed only when creating action descriptors, then they can be deallocated
        services.TryAddSingleton();
        services.TryAddEnumerable(
            ServiceDescriptor.Transient<IApplicationModelProvider, DefaultApplicationModelProvider>());
        services.TryAddEnumerable(
            ServiceDescriptor.Transient<IApplicationModelProvider, ApiBehaviorApplicationModelProvider>());
        services.TryAddEnumerable(
            ServiceDescriptor.Transient<IActionDescriptorProvider, ControllerActionDescriptorProvider>());

        services.TryAddSingleton<IActionDescriptorCollectionProvider, DefaultActionDescriptorCollectionProvider>();

        //
        // Action Selection
        //
        services.TryAddSingleton<IActionSelector, ActionSelector>();
        services.TryAddSingleton();

        // Will be cached by the DefaultActionSelector
        services.TryAddEnumerable(ServiceDescriptor.Transient<IActionConstraintProvider, DefaultActionConstraintProvider>());

        // Policies for Endpoints
        services.TryAddEnumerable(ServiceDescriptor.Singleton<MatcherPolicy, ActionConstraintMatcherPolicy>());

        //
        // Controller Factory
        //
        // This has a cache, so it needs to be a singleton
        services.TryAddSingleton<IControllerFactory, DefaultControllerFactory>();

        // Will be cached by the DefaultControllerFactory
        services.TryAddTransient<IControllerActivator, DefaultControllerActivator>();

        services.TryAddSingleton<IControllerFactoryProvider, ControllerFactoryProvider>();
        services.TryAddSingleton<IControllerActivatorProvider, ControllerActivatorProvider>();
        services.TryAddEnumerable(
            ServiceDescriptor.Transient<IControllerPropertyActivator, DefaultControllerPropertyActivator>());

        //
        // Action Invoker
        //
        // The IActionInvokerFactory is cachable
        services.TryAddSingleton<IActionInvokerFactory, ActionInvokerFactory>();
        services.TryAddEnumerable(
            ServiceDescriptor.Transient<IActionInvokerProvider, ControllerActionInvokerProvider>());

        // These are stateless
        services.TryAddSingleton();
        services.TryAddEnumerable(
            ServiceDescriptor.Singleton<IFilterProvider, DefaultFilterProvider>());
        services.TryAddSingleton<IActionResultTypeMapper, ActionResultTypeMapper>();

        //
        // Request body limit filters
        //
        services.TryAddTransient();
        services.TryAddTransient();
        services.TryAddTransient();

        //
        // ModelBinding, Validation
        //
        // The DefaultModelMetadataProvider does significant caching and should be a singleton.
        services.TryAddSingleton<IModelMetadataProvider, DefaultModelMetadataProvider>();
        services.TryAdd(ServiceDescriptor.Transient(s =>
        {
            var options = s.GetRequiredService<IOptions>().Value;
            return new DefaultCompositeMetadataDetailsProvider(options.ModelMetadataDetailsProviders);
        }));
        services.TryAddSingleton<IModelBinderFactory, ModelBinderFactory>();
        services.TryAddSingleton(s =>
        {
            var options = s.GetRequiredService<IOptions>().Value;
            var metadataProvider = s.GetRequiredService();
            return new DefaultObjectValidator(metadataProvider, options.ModelValidatorProviders, options);
        });
        services.TryAddSingleton();
        services.TryAddSingleton();

        //
        // Random Infrastructure
        //
        services.TryAddSingleton<MvcMarkerService, MvcMarkerService>();
        services.TryAddSingleton<ITypeActivatorCache, TypeActivatorCache>();
        services.TryAddSingleton<IUrlHelperFactory, UrlHelperFactory>();
        services.TryAddSingleton<IHttpRequestStreamReaderFactory, MemoryPoolHttpRequestStreamReaderFactory>();
        services.TryAddSingleton<IHttpResponseStreamWriterFactory, MemoryPoolHttpResponseStreamWriterFactory>();
        services.TryAddSingleton(ArrayPool.Shared);
        services.TryAddSingleton(ArrayPool.Shared);
        services.TryAddSingleton<OutputFormatterSelector, DefaultOutputFormatterSelector>();
        services.TryAddSingleton<IActionResultExecutor, ObjectResultExecutor>();
        services.TryAddSingleton<IActionResultExecutor, PhysicalFileResultExecutor>();
        services.TryAddSingleton<IActionResultExecutor, VirtualFileResultExecutor>();
        services.TryAddSingleton<IActionResultExecutor, FileStreamResultExecutor>();
        services.TryAddSingleton<IActionResultExecutor, FileContentResultExecutor>();
        services.TryAddSingleton<IActionResultExecutor, RedirectResultExecutor>();
        services.TryAddSingleton<IActionResultExecutor, LocalRedirectResultExecutor>();
        services.TryAddSingleton<IActionResultExecutor, RedirectToActionResultExecutor>();
        services.TryAddSingleton<IActionResultExecutor, RedirectToRouteResultExecutor>();
        services.TryAddSingleton<IActionResultExecutor, RedirectToPageResultExecutor>();
        services.TryAddSingleton<IActionResultExecutor, ContentResultExecutor>();
        services.TryAddSingleton<IActionResultExecutor, SystemTextJsonResultExecutor>();
        services.TryAddSingleton<IClientErrorFactory, ProblemDetailsClientErrorFactory>();
        services.TryAddSingleton<ProblemDetailsFactory, DefaultProblemDetailsFactory>();

        //
        // Route Handlers
        //
        services.TryAddSingleton(); // Only one per app
        services.TryAddTransient(); // Many per app

        //
        // Endpoint Routing / Endpoints
        //
        services.TryAddSingleton();
        services.TryAddSingleton();
        services.TryAddSingleton();
        services.TryAddSingleton();
        services.TryAddSingleton();
        services.TryAddEnumerable(ServiceDescriptor.Singleton<MatcherPolicy, DynamicControllerEndpointMatcherPolicy>());
        services.TryAddEnumerable(ServiceDescriptor.Singleton<IRequestDelegateFactory, ControllerRequestDelegateFactory>());

        //
        // Middleware pipeline filter related
        //
        services.TryAddSingleton();
        // This maintains a cache of middleware pipelines, so it needs to be a singleton
        services.TryAddSingleton();
        // Sets ApplicationBuilder on MiddlewareFilterBuilder
        services.TryAddEnumerable(ServiceDescriptor.Singleton<IStartupFilter, MiddlewareFilterBuilderStartupFilter>());
    }
}

下面的PopulateDefaultParts()方法从当前程序集找到所有引用到了的程序集（包括[assembly:ApplicationPart(“demo”)]中标记的）把他们封装成ApplciationPart，然后把他们放在了ApplciationPartManager的ApplicationParts属性中，用于后面筛选Controller提供数据基础。

namespace Microsoft.AspNetCore.Mvc.ApplicationParts
{
    /// 
    /// Manages the parts and features of an MVC application.
    /// 
    public class ApplicationPartManager
    {

        /// 
        /// Gets the list of  instances.
        /// 
        /// Instances in this collection are stored in precedence order. An  that appears
        /// earlier in the list has a higher precedence.
        /// An  may choose to use this an interface as a way to resolve conflicts when
        /// multiple  instances resolve equivalent feature values.
        /// 
        /// 
        public IList ApplicationParts { get; } = new List();

        internal void PopulateDefaultParts(string entryAssemblyName)
        {
            //获取相关联的程序集
            var assemblies = GetApplicationPartAssemblies(entryAssemblyName);

            var seenAssemblies = new HashSet();

            foreach (var assembly in assemblies)
            {
                if (!seenAssemblies.Add(assembly))
                {
                    // "assemblies" may contain duplicate values, but we want unique ApplicationPart instances.
                    // Note that we prefer using a HashSet over Distinct since the latter isn't
                    // guaranteed to preserve the original ordering.
                    continue;
                }

                var partFactory = ApplicationPartFactory.GetApplicationPartFactory(assembly);
                foreach (var applicationPart in partFactory.GetApplicationParts(assembly))
                {
                    ApplicationParts.Add(applicationPart);
                }
            }
        }

        private static IEnumerable GetApplicationPartAssemblies(string entryAssemblyName)
        {
            //加载当前主程序集
            var entryAssembly = Assembly.Load(new AssemblyName(entryAssemblyName));

            // Use ApplicationPartAttribute to get the closure of direct or transitive dependencies
            // that reference MVC.
            var assembliesFromAttributes = entryAssembly.GetCustomAttributes()
                .Select(name => Assembly.Load(name.AssemblyName))
                .OrderBy(assembly => assembly.FullName, StringComparer.Ordinal)
                .SelectMany(GetAssemblyClosure);

            // The SDK will not include the entry assembly as an application part. We'll explicitly list it
            // and have it appear before all other assemblies \ ApplicationParts.
            return GetAssemblyClosure(entryAssembly)
                .Concat(assembliesFromAttributes);
        }

        private static IEnumerable GetAssemblyClosure(Assembly assembly)
        {
            yield return assembly;

            var relatedAssemblies = RelatedAssemblyAttribute.GetRelatedAssemblies(assembly, throwOnError: false)
                .OrderBy(assembly => assembly.FullName, StringComparer.Ordinal);

            foreach (var relatedAssembly in relatedAssemblies)
            {
                yield return relatedAssembly;
            }
        }
    }
}

MapControllers

它的主要作用是将controllerl里面的action映射为我们的终结点。我们接下来看下Controller里的Action是怎样注册到路由模块的。MapControllers()方法执行时就会遍历遍历已经收集到的ApplicationPart进而将其中Controller里面的Action方法转换封装成一个个的EndPoint放到路由中间件的配置对象RouteOptions中然后交给Routing模块处理。前面提到EndpointMiddleware的一大核心代码主要是执行Endpoint 的RequestDelegate 委托，也即对Controller 中的Action 的执行。所有的Http请求都会走到EndpointMiddleware中间件中，然后去执行对应的Action。在应用程序启动的时候会把我们的所有的路由信息添加到一个EndpointSource的集合中去的，所以在MapController方法，其实就是在构建我们所有的路由请求的一个RequestDelegate，然后在每次请求的时候，在EndpointMiddleWare中间件去执行这个RequestDelegate，从而走到我们的接口中去。简而言之，这个方法就是将我们的所有路由信息添加到一个EndpointDataSource的抽象类的实现类中去，默认是ControllerActionEndpointDataSource这个类，在这个类中有一个基类ActionEndpointDataSourceBase，ControllerActionEndpointDataSource初始化的时候会订阅所有的Endpoint的集合的变化，每变化一次会向EndpointSource集合添加Endpoint，从而在请求的时候可以找到这个终结点去调用。

我们来看下MapControllers()的源码

public static class ControllerEndpointRouteBuilderExtensions
{
    ///
    /// Adds endpoints for controller actions to the without specifying any routes.
    ///
    ///The .
    /// An  for endpoints associated with controller actions.
    public static ControllerActionEndpointConventionBuilder MapControllers(this IEndpointRouteBuilder endpoints)
    {
        if (endpoints == null)
        {
            throw new ArgumentNullException(nameof(endpoints));
        }

        EnsureControllerServices(endpoints);

        return GetOrCreateDataSource(endpoints).DefaultBuilder;
    }

    private static void EnsureControllerServices(IEndpointRouteBuilder endpoints)
    {
        var marker = endpoints.ServiceProvider.GetService();
        if (marker == null)
        {
            throw new InvalidOperationException(Resources.FormatUnableToFindServices(
                nameof(IServiceCollection),
                "AddControllers",
                "ConfigureServices(...)"));
        }
    }

    private static ControllerActionEndpointDataSource GetOrCreateDataSource(IEndpointRouteBuilder endpoints)
    {
        var dataSource = endpoints.DataSources.OfType().FirstOrDefault();
        if (dataSource == null)
        {
            var orderProvider = endpoints.ServiceProvider.GetRequiredService();
            var factory = endpoints.ServiceProvider.GetRequiredService();
            dataSource = factory.Create(orderProvider.GetOrCreateOrderedEndpointsSequenceProvider(endpoints));
            endpoints.DataSources.Add(dataSource);
        }

        return dataSource;
    }
}

首先EnsureControllerServices方法检查mvc服务是否注入了，GetOrCreateDataSource方法执行完就获取到了dateSource,dateSource中就是所有的Action信息。需要注意的是ControllerActionEndpointDataSource这个类，它里面的方法帮我们创建路由终结点。我们来看一下它的定义：

internal class ControllerActionEndpointDataSource : ActionEndpointDataSourceBase
{
    private readonly ActionEndpointFactory _endpointFactory;
    private readonly OrderedEndpointsSequenceProvider _orderSequence;
    private readonly List _routes;

    public ControllerActionEndpointDataSource(
        ControllerActionEndpointDataSourceIdProvider dataSourceIdProvider,
        IActionDescriptorCollectionProvider actions,
        ActionEndpointFactory endpointFactory,
        OrderedEndpointsSequenceProvider orderSequence)
        : base(actions)
    {
        _endpointFactory = endpointFactory;

        DataSourceId = dataSourceIdProvider.CreateId();
        _orderSequence = orderSequence;

        _routes = new List();

        DefaultBuilder = new ControllerActionEndpointConventionBuilder(Lock, Conventions);

        // IMPORTANT: this needs to be the last thing we do in the constructor.
        // Change notifications can happen immediately!
        Subscribe();
    }

    public int DataSourceId { get; }

    public ControllerActionEndpointConventionBuilder DefaultBuilder { get; }

    // Used to control whether we create 'inert' (non-routable) endpoints for use in dynamic
    // selection. Set to true by builder methods that do dynamic/fallback selection.
    public bool CreateInertEndpoints { get; set; }

    public ControllerActionEndpointConventionBuilder AddRoute(
        string routeName,
        string pattern,
        RouteValueDictionary? defaults,
        IDictionary<string, object?>? constraints,
        RouteValueDictionary? dataTokens)
    {
        lock (Lock)
        {
            var conventions = new List<Action>();
            _routes.Add(new ConventionalRouteEntry(routeName, pattern, defaults, constraints, dataTokens, _orderSequence.GetNext(), conventions));
            return new ControllerActionEndpointConventionBuilder(Lock, conventions);
        }
    }

    protected override List CreateEndpoints(IReadOnlyList actions, IReadOnlyList<Action> conventions)
    {
        var endpoints = new List();
        var keys = new HashSet(StringComparer.OrdinalIgnoreCase);

        // MVC guarantees that when two of it's endpoints have the same route name they are equivalent.
        //
        // However, Endpoint Routing requires Endpoint Names to be unique.
        var routeNames = new HashSet(StringComparer.OrdinalIgnoreCase);

        // For each controller action - add the relevant endpoints.
        //
        // 1. If the action is attribute routed, we use that information verbatim
        // 2. If the action is conventional routed
        //      a. Create a *matching only* endpoint for each action X route (if possible)
        //      b. Ignore link generation for now
        for (var i = 0; i < actions.Count; i++)
        {
            if (actions[i] is ControllerActionDescriptor action)
            {
                _endpointFactory.AddEndpoints(endpoints, routeNames, action, _routes, conventions, CreateInertEndpoints);

                if (_routes.Count > 0)
                {
                    // If we have conventional routes, keep track of the keys so we can create
                    // the link generation routes later.
                    foreach (var kvp in action.RouteValues)
                    {
                        keys.Add(kvp.Key);
                    }
                }
            }
        }

        // Now create a *link generation only* endpoint for each route. This gives us a very
        // compatible experience to previous versions.
        for (var i = 0; i < _routes.Count; i++)
        {
            var route = _routes[i];
            _endpointFactory.AddConventionalLinkGenerationRoute(endpoints, routeNames, keys, route, conventions);
        }

        return endpoints;
    }

    internal void AddDynamicControllerEndpoint(IEndpointRouteBuilder endpoints, string pattern, Type transformerType, object? state, int? order = null)
    {
        CreateInertEndpoints = true;
        lock (Lock)
        {
            order ??= _orderSequence.GetNext();

            endpoints.Map(
                pattern,
                context =>
                {
                    throw new InvalidOperationException("This endpoint is not expected to be executed directly.");
                })
                .Add(b =>
                {
                    ((RouteEndpointBuilder)b).Order = order.Value;
                    b.Metadata.Add(new DynamicControllerRouteValueTransformerMetadata(transformerType, state));
                    b.Metadata.Add(new ControllerEndpointDataSourceIdMetadata(DataSourceId));
                });
        }
    }
}

在CreateEndpoints方法中会遍历每个ActionDescriptor对象，ActionDescriptor对象里面存储的是Action方法的元数据。然后创建一个个的Endpoint实例，Endpoint对象里面有一个RequestDelegate参数，当请求进入的时候会执行这个委托进入对应的Action。另外这其中还有一个DefaultBuilder属性，可以看到他返回的是ControllerActionEndpointConventionBuilder对象，这个对象是用来构建约定路由的。AddRoute方法也是用来添加约定路由的。我们再来看下构造函数中的Subscribe()方法，这个方法是调用父类ActionEndpointDataSourceBase中的。我们来看一下这个类：

internal abstract class ActionEndpointDataSourceBase : EndpointDataSource, IDisposable
{
    private readonly IActionDescriptorCollectionProvider _actions;

    // The following are protected by this lock for WRITES only. This pattern is similar
    // to DefaultActionDescriptorChangeProvider - see comments there for details on
    // all of the threading behaviors.
    protected readonly object Lock = new object();

    // Protected for READS and WRITES.
    protected readonly List<Action> Conventions;

    private List? _endpoints;
    private CancellationTokenSource? _cancellationTokenSource;
    private IChangeToken? _changeToken;
    private IDisposable? _disposable;

    public ActionEndpointDataSourceBase(IActionDescriptorCollectionProvider actions)
    {
        _actions = actions;

        Conventions = new List<Action>();
    }

    public override IReadOnlyList Endpoints
    {
        get
        {
            Initialize();
            Debug.Assert(_changeToken != null);
            Debug.Assert(_endpoints != null);
            return _endpoints;
        }
    }

    // Will be called with the lock.
    protected abstract List CreateEndpoints(IReadOnlyList actions, IReadOnlyList<Action> conventions

    protected void Subscribe()
    {
        // IMPORTANT: this needs to be called by the derived class to avoid the fragile base class
        // problem. We can't call this in the base-class constuctor because it's too early.
        //
        // It's possible for someone to override the collection provider without providing
        // change notifications. If that's the case we won't process changes.
        if (_actions is ActionDescriptorCollectionProvider collectionProviderWithChangeToken)
        {
            _disposable = ChangeToken.OnChange(
                () => collectionProviderWithChangeToken.GetChangeToken(),
                UpdateEndpoints);
        }
    }

    public override IChangeToken GetChangeToken()
    {
        Initialize();
        Debug.Assert(_changeToken != null);
        Debug.Assert(_endpoints != null);
        return _changeToken;
    }

    public void Dispose()
    {
        // Once disposed we won't process updates anymore, but we still allow access to the endpoints.
        _disposable?.Dispose();
        _disposable = null;
    }

    private void Initialize()
    {
        if (_endpoints == null)
        {
            lock (Lock)
            {
                if (_endpoints == null)
                {
                    UpdateEndpoints();
                }
            }
        }
    }

    private void UpdateEndpoints()
    {
        lock (Lock)
        {
            var endpoints = CreateEndpoints(_actions.ActionDescriptors.Items, Conventions);

            // See comments in DefaultActionDescriptorCollectionProvider. These steps are done
            // in a specific order to ensure callers always see a consistent state.

            // Step 1 - capture old token
            var oldCancellationTokenSource = _cancellationTokenSource;

            // Step 2 - update endpoints
            _endpoints = endpoints;

            // Step 3 - create new change token
            _cancellationTokenSource = new CancellationTokenSource();
            _changeToken = new CancellationChangeToken(_cancellationTokenSource.Token);

            // Step 4 - trigger old token
            oldCancellationTokenSource?.Cancel();
        }
    }
}

_actions属性是注入进来的，这个对象是我们在services.AddMvcCore()中注入进来的：services.TryAddSingleton<IActionDescriptorCollectionProvider, DefaultActionDescriptorCollectionProvider>();我们来说下ChangeToken.OnChange()方法，他里面有两个委托类型的参数，GetChangeToken()它的作用是用来感知ActionDescriptor数据源的变化，然后执行UpdateEndpoints方法中的具体的逻辑：

• 首先更新ActionDescriptors对象的具体元数据信息
• 获取旧的令牌
• 更新终结点
• 创建新的令牌
• 废弃旧的令牌

大家做的项目都有鉴权、授权的功能。而每一个角色可以访问的资源是不相同的，因此策略鉴权是非常关键的一步，它可以阻止非此菜单资源的角色用户访问此菜单的接口。一般来说有一个接口表(Module)、一个菜单表(Permission)、一个接口菜单关系表(ModulePermission)，接口需要挂在菜单下面，假如一个项目几百个接口，那录起来可就麻烦了。按照我们上面说的，在管道构建时，程序就会扫描所有相关程序集中Controller的Action然后交给“路由”模块去管理。Action的这些元数据信息会存在我们上面说的IActionDescriptorCollectionProvider中的ActionDescriptorCollection对象的ActionDescriptor集合中，这样在http请求到来时“路由”模块才能寻找到正确的Endpoint，进而找到Action并调用执行。那么我们就可以读到项目中所有注册的路由，然后导入到数据库表中😊

private readonly IActionDescriptorCollectionProvider _actionDescriptorCollectionProvider;

public RouteController(IActionDescriptorCollectionProvider actionDescriptorCollectionProvider)
{
    _actionDescriptorCollectionProvider = actionDescriptorCollectionProvider;
}
/// <summary>
/// 获取路由
/// </summary>
/// <returns></returns>
[HttpGet]
public IActionResult Get()
{
    var routes = _actionDescriptorCollectionProvider.ActionDescriptors.Items.Select(x => new
    {
        Action = x.RouteValues["Action"],
        Controller = x.RouteValues["Controller"],
        Name = x.AttributeRouteInfo.Name,
        Method = x.ActionConstraints?.OfType<HttpMethodActionConstraint>().FirstOrDefault()?.HttpMethods.First(),
        Template = x.AttributeRouteInfo.Template
    }).ToList();
    return Ok(routes);
}

上面我们聊了一些源码，接下来我们来看下如何实现动态路由

MvcOptions

先说一下MvcOptions类，它为.Net Core 整个框架提供基础配置。这样说估计太抽象了，我举例一下哈。例如Action加上[FromBody]，客户端传入的Body为null的话，接口会报400错误：A non-empty request body is required。可以使用模型验证AllowEmptyInputInBodyModelBinding参数配置null值可传入（.Net5之后可以根据需要按请求进行配置）。还有FilterCollection集合这个参数，从MVC时代沿用到现在的五种资源过滤器，其实他们都默认继承自IFilterMetadata空接口，而FilterCollection集合就是承载这些Filter的容器且继承自Collection<IFilterMetadata>，关于AOP和管道中间件这些我后面会单独抽源码来讲。好了我们这篇主要要说一下它里面的IList<IApplicationModelConvention>参数。

IApplicationModelConvention

我们先看下它的源码：

我们可以写一个类继承它，实现它的Apply方法，修改.Net Core程序内部对路由、控制器的默认生成行为，然后将它添加到Convention集合中😊

通过Apply方法来进行自定义，可以修改的内容由ApplicationModel对象提供。特别是它里面的ControllerModel对象，有了它我们可以直接对控制器进行各种配置和操作。

看一下ApplicationModel对象的定义：

/// <summary>
/// A model for configuring controllers in an MVC application.
/// </summary>
[DebuggerDisplay("ApplicationModel: Controllers: {Controllers.Count}, Filters: {Filters.Count}")]
public class ApplicationModel : IPropertyModel, IFilterModel, IApiExplorerModel
{
    /// <summary>
    /// Initializes a new instance of <see cref="ApplicationModel"/>.
    /// </summary>
    public ApplicationModel()
    {
        ApiExplorer = new ApiExplorerModel();
        Controllers = new List<ControllerModel>();
        Filters = new List<IFilterMetadata>();
        Properties = new Dictionary<object, object?>();
    }
    /// <summary>
    /// Gets or sets the <see cref="ApiExplorerModel"/> for the application.
    /// </summary>
    /// <remarks>
    /// <see cref="ApplicationModel.ApiExplorer"/> allows configuration of default settings
    /// for ApiExplorer that apply to all actions unless overridden by
    /// <see cref="ControllerModel.ApiExplorer"/> or <see cref="ActionModel.ApiExplorer"/>.
    ///
    /// If using <see cref="ApplicationModel.ApiExplorer"/> to set <see cref="ApiExplorerModel.IsVisible"/> to
    /// <c>true</c>, this setting will only be honored for actions which use attribute routing.
    /// </remarks>
    public ApiExplorerModel ApiExplorer { get; set; }
    /// <summary>
    /// Gets the <see cref="ControllerModel"/> instances.
    /// </summary>
    public IList<ControllerModel> Controllers { get; }
    /// <summary>
    /// Gets the global <see cref="IFilterMetadata"/> instances.
    /// </summary>
    public IList<IFilterMetadata> Filters { get; }
    /// <summary>
    /// Gets a set of properties associated with all actions.
    /// These properties will be copied to <see cref="Abstractions.ActionDescriptor.Properties"/>.
    /// </summary>
    public IDictionary<object, object?> Properties { get; }
}

①ApiExplorer可以用来配置控制器的组信息还有可见性

②Controllers可以获取Controller的相关信息，再借助IControllerModelConvention对其进行定制扩展

③Filters存放的都是空接口，起到标记作用，换句话说就是在请求管道构建的时候用于判断是否为Filter类

④Properties属于共享字典

给路由添加全局配置

services.AddControllers(options =>
{
    options.UseCentralRoutePrefix(new RouteAttribute("core/v1/api/[controller]/[action]"));
});

添加我们自定义扩展方法

public static class MvcOptionsExtensions
{
    /// <summary>
    /// 扩展方法
    /// </summary>
    /// <param name="opts"></param>
    /// <param name="routeAttribute"></param>
    public static void UseCentralRoutePrefix(this MvcOptions opts, IRouteTemplateProvider routeAttribute)
    {
        //添加我们自定义实现
        opts.Conventions.Insert(0, new RouteConvention(routeAttribute));
    }
}

 具体的实现类

/// <summary>
/// 全局路由前缀配置
/// </summary>
public class RouteConvention : IApplicationModelConvention
{
    /// <summary>
    /// 定义一个路由前缀变量
    /// </summary>
    private readonly AttributeRouteModel _centralPrefix;
    /// <summary>
    /// 调用时传入指定的路由前缀
    /// </summary>
    /// <param name="routeTemplateProvider"></param>
    public RouteConvention(IRouteTemplateProvider routeTemplateProvider)
    {
        _centralPrefix = new AttributeRouteModel(routeTemplateProvider);
    }

    //实现Apply方法
    public void Apply(ApplicationModel application)
    {
        //遍历所有的 Controller
        foreach (var controller in application.Controllers)
        {　　　　　　　
            var matchedSelectors = controller.Selectors.Where(x => x.AttributeRouteModel != null).ToList();
            if (matchedSelectors.Any())//该Controller已经标记了RouteAttribute
            {
                foreach (var selectorModel in matchedSelectors)
                {
                    // 在当前路由上再添加一个 路由前缀
                    selectorModel.AttributeRouteModel = AttributeRouteModel.CombineAttributeRouteModel(_centralPrefix,
                        selectorModel.AttributeRouteModel);
                }
            }

            var unmatchedSelectors = controller.Selectors.Where(x => x.AttributeRouteModel == null).ToList();
            if (unmatchedSelectors.Any())//该Controller没有标记RouteAttribute
            {
                foreach (var selectorModel in unmatchedSelectors)
                {
                    // 添加一个路由前缀
                    selectorModel.AttributeRouteModel = _centralPrefix;
                }
            }
        }
    }
}

POCO控制器

在Java中有一个叫POJO的名词，即"Plain Old Java Object"，直译就是简单的Java对象，其实它表示的是没有继承任何类，也没有实现任何接口的对象。在C#中也有一个相同含义的名词叫POCO（Plain Old C# Object）,两者表示的含义是一样的。在.Net Core中有一个POCO Controller的特性，它不用继承Controller或ControllerBase，只需要在类名后加上Controller的后缀或标记[Controller]特性也能拥有Controller的功能。

下面简单演示一下：

public class TestController
{

    [HttpGet]
    public async Task<IEnumerable<int>> Get()
    {
        Func<int, int> triple = m => m * 3;
        var range = Enumerable.Range(1, 3);
        return range.Select(triple);
    }
}

[Controller]
public class TestOnce
{
    [HttpGet]
    public async Task<IEnumerable<dynamic>> Index()
    => Enumerable.Range(1, 100).Select(triple => new { triple });

}

 上面两个类中的Action会被正确扫描并添加到终结点中：

一个(控制器)类如果加上[NonController]就不会被注册到路由中😋。我们接下来还是看下源码：

// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.

using System.Linq;
using System.Reflection;
using Microsoft.AspNetCore.Mvc.ApplicationParts;

namespace Microsoft.AspNetCore.Mvc.Controllers;

/// <summary>
/// Discovers controllers from a list of <see cref="ApplicationPart"/> instances.
/// </summary>
public class ControllerFeatureProvider : IApplicationFeatureProvider<ControllerFeature>
{
    private const string ControllerTypeNameSuffix = "Controller";

    /// <inheritdoc />
    public void PopulateFeature(
        IEnumerable<ApplicationPart> parts,
        ControllerFeature feature)
    {
        foreach (var part in parts.OfType<IApplicationPartTypeProvider>())
        {
            foreach (var type in part.Types)
            {
                if (IsController(type) && !feature.Controllers.Contains(type))
                {
                    feature.Controllers.Add(type);
                }
            }
        }
    }

    /// <summary>
    /// Determines if a given <paramref name="typeInfo"/> is a controller.
    /// </summary>
    /// <param name="typeInfo">The <see cref="TypeInfo"/> candidate.</param>
    /// <returns><see langword="true" /> if the type is a controller; otherwise <see langword="false" />.</returns>
    protected virtual bool IsController(TypeInfo typeInfo)
    {
        if (!typeInfo.IsClass)
        {
            return false;
        }

        if (typeInfo.IsAbstract)
        {
            return false;
        }

        // We only consider public top-level classes as controllers. IsPublic returns false for nested
        // classes, regardless of visibility modifiers
        if (!typeInfo.IsPublic)
        {
            return false;
        }

        if (typeInfo.ContainsGenericParameters)
        {
            return false;
        }

        if (typeInfo.IsDefined(typeof(NonControllerAttribute)))
        {
            return false;
        }

        if (!typeInfo.Name.EndsWith(ControllerTypeNameSuffix, StringComparison.OrdinalIgnoreCase) &&
            !typeInfo.IsDefined(typeof(ControllerAttribute)))
        {
            return false;
        }

        return true;
    }
}

其实POCO控制器的核心就在于IApplicationFeatureProvider<ControllerFeature>这个接口，ControllerFeatureProvider是其默认的实现类。

我们重新写一个类继承自ControllerFeatureProvider，把IsController方法进行重写加入我们的判断逻辑，其它我就不啰嗦了，上面的代码很清楚白了了😆

自定义控制器规则

定义一个接口和一个特性使之成为我们的规则

public interface ICoreDynamicController { }

[AttributeUsage(AttributeTargets.Class, Inherited = true)]
public class CoreDynamicControllerAttribute : Attribute { }

继承ControllerFeatureProvider类并且实现IsController方法：

public class CoreDynamicExtendControlleFeatureProvider : ControllerFeatureProvider
{
    protected override bool IsController(TypeInfo typeInfo)
    {
        var type = typeInfo.AsType();
        if ((typeof(ICoreDynamicController).IsAssignableFrom(type) || //判断是否继承ICoreDynamicController接口
            type.IsDefined(typeof(CoreDynamicControllerAttribute), true) || // 判断是否标记了ICoreDynamicController特性
            type.BaseType == typeof(Microsoft.AspNetCore.Mvc.Controller)) && //判断基类型是否是Controller
            (typeInfo.IsPublic && !typeInfo.IsAbstract && !typeInfo.IsGenericType && !typeInfo.IsInterface)) //必须是Public、不能是抽象类、必须是非泛型的
        {
          return true;
        }
        return false;
    }
}

 现在方法已经写好了，但是我们要把它配置到Mvc中才行。这里要说一下MvcCoreMvcBuilderExtensions类的IMvcBuilder的ConfigureApplicationPartManager方法，它的参数是一个委托，委托中的参数是ApplicationPartManager， ApplicationPartManager中有一个FeatureProviders的属性，它里面全是IApplicationFeatureProvider的实例。程序启动的时候会循环这些实例，我们把自己的自定义实现类添加进来，这样Core程序就能识别我们的控制器，并且赋予其控制器所有的功能。无图无真相，请看源码：

 所以把我们自定义的识别类添加进来即可

services.AddControllers().ConfigureApplicationPartManager
(t => t.FeatureProviders.Add(new CoreDynamicExtendControlleFeatureProvider()));

 如下示例：

public class Test : ICoreDynamicController
{

    [HttpGet]
    public IEnumerable<int> Get(int value)
    {
        yield return value;
    }
}

Dynamic Api

使用过ABP vNext框架的小伙伴都应该知道，如果一个类实现了IRemoteService或IApplicationService接口，那么它会被自动选择为API控制器。ABP vNext框架在动态API功能中遵从约定大于配置的原则，例如方法名称以GetList,GetAll或Get开头则请求的HttpMethod都为HttpGet

ABP vNext官方文档：API/Auto API Controllers | Documentation Center | ABP.IO

我们借助它的思想来实现我们的动态API

实现Apply方法

在AspNetCore框架中给出了三个配置控制器、方法和参数的配置接口，分别是IControllerModelConvention、IActionModelConvention和IParameterModelConvention。在它们的Apply方法中，传入了一个 MVC 启动阶段扫描到的类型，对应的分别是ControllerModel、ActionModel和ParameterModel我们可以通过这三个Model加入我们的自定义配置。还是一样我们要继承IApplicationModelConvention接口筛选出符合条件的控制器，然后遍历其中的Action给其添加路由与HttpMethos（要根据Action的前缀进行判断）。本项目是根据下面列举的条件进行判断的（注意：得到ActionMethodName的时候要ToUpper或ToLower这样方便判断）：

• Get：如果方法以GET、QUERY开头
• Post：如果方法以CREATE、SAVE、INSERT、ADD开头
• Put：如果方法以UPDATE、EDIT开头
• Delete：如果方法以Delete、REMOVE开头

"HttpMethodInfo": [
  {
    "MethodKey": "Get",
    "MethodVal": [ "GET", "QUERY" ]
  },
  {
    "MethodKey": "Post",
    "MethodVal": [ "CREATE", "SAVE", "INSERT", "ADD" ]
  },
  {
    "MethodKey": "Put",
    "MethodVal": [ "UPDATE", "EDIT" ]
  },
  {
    "MethodKey": "Delete",
    "MethodVal": [ "Delete", "REMOVE" ]
  }
]

public class CoreDynamicControllerConvention : IApplicationModelConvention
{
    private IConfiguration _configuration;
    private List<HttpMethodConfigure> httpMethods = new();
    public CoreDynamicControllerConvention(IConfiguration configuration)
    {
        _configuration = configuration;
        httpMethods = (List<HttpMethodConfigure>)_configuration.GetSection("HttpMethodInfo").Get(typeof(List<HttpMethodConfigure>));
    }
    public void Apply(ApplicationModel application)
    {
        //循环每一个控制器信息
        foreach (var controller in application.Controllers)
        {
            var controllerType = controller.ControllerType.AsType();
            //是否继承ICoreDynamicController接口
            if (typeof(ICoreDynamicController).IsAssignableFrom(controllerType))
            {
                foreach (var item in controller.Actions)
                {
                    ConfigureSelector(controller.ControllerName, item);
                }
            }
        }
    }

    private void ConfigureSelector(string controllerName, ActionModel action)
    {
        for (int i = 0; i < action.Selectors.Count; i++)
        {
            if (action.Selectors[i].AttributeRouteModel is null)
                action.Selectors.Remove(action.Selectors[i]);
        }

        if (action.Selectors.Any())
        {
            foreach (var item in action.Selectors)
            {
                var routePath = string.Concat("api/", controllerName, action.ActionName).Replace("//", "/");
                var routeModel = new AttributeRouteModel(new RouteAttribute(routePath));
                //如果没有路由属性
                if (item.AttributeRouteModel == null) item.AttributeRouteModel = routeModel;
            }
        }
        else
        {
            action.Selectors.Add(CreateActionSelector(controllerName, action));
        }
    }

    private SelectorModel CreateActionSelector(string controllerName, ActionModel action)
    {
        var selectorModel = new SelectorModel();
        var actionName = action.ActionName;
        string httpMethod = string.Empty;
        //是否有HttpMethodAttribute
        var routeAttributes = action.ActionMethod.GetCustomAttributes(typeof(HttpMethodAttribute), false);
        //如果标记了HttpMethodAttribute
        if (routeAttributes != null && routeAttributes.Any())
        {
            httpMethod = routeAttributes.SelectMany(m => (m as HttpMethodAttribute).HttpMethods).ToList().Distinct().FirstOrDefault();
        }
        else
        {
            var methodName = action.ActionMethod.Name.ToUpper();

            foreach (var item in httpMethods)
            {
                if (item.MethodVal.Contains(methodName))
                {
                    httpMethod = item.MethodKey;
                    break;
                }
            }
        }
        return ConfigureSelectorModel(selectorModel, action, controllerName, httpMethod);
    }

    public SelectorModel ConfigureSelectorModel(SelectorModel selectorModel, ActionModel action, string controllerName, string httpMethod)
    {
        var routePath = string.Concat("api/", controllerName, action.ActionName).Replace("//", "/");
        //给此Action添加路由
        selectorModel.AttributeRouteModel = new AttributeRouteModel(new RouteAttribute(routePath));
        //添加HttpMethod
        selectorModel.ActionConstraints.Add(new HttpMethodActionConstraint(new[] { httpMethod }));
        return selectorModel;
    }
}

控制器中就很简单了：

public class Test : IDynamicController
{
    private readonly IHttpContextAccessor _httpAccessor;
    public Test(IHttpContextAccessor httpAccessor) => _httpAccessor = httpAccessor;

    public async Task SaveData()
    => _httpAccessor.HttpContext.Response.WriteAsJsonAsync(new { _ = this.GetType() });

    public async Task DeleteData()
    => _httpAccessor.HttpContext.Response.WriteAsJsonAsync(new { _ = this.GetType() });

    public async Task QueryData()
    => _httpAccessor.HttpContext.Response.WriteAsJsonAsync(new { _ = this.GetType() });

    public async Task UpdateData()
    => _httpAccessor.HttpContext.Response.WriteAsJsonAsync(new { _ = this.GetType() });
}

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