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使用.Net6中的WebApplication打造最小API_自學(xué)過程

作者：a1010 ? 更新時間： 2022-03-10 編程語言

.net6在preview4時給我們帶來了一個新的API：WebApplication，通過這個API我們可以打造更小的輕量級API服務(wù)。今天我們來嘗試一下如何使用WebApplication設(shè)計一個小型API服務(wù)系統(tǒng)。

環(huán)境準(zhǔn)備

  • .NETSDK v6.0.0-preview.5.21355.2
  • Visual Studio 2022 Preview

首先看看原始版本的WebApplication，官方已經(jīng)提供了樣例模板，打開我們的vs2022,選擇新建項目選擇asp.net core empty，framework選擇.net6.0(preview)點擊創(chuàng)建，即可生成一個簡單的最小代碼示例：

如果我們在.csproj里在配置節(jié)PropertyGroup增加使用C#10新語法讓自動進(jìn)行類型推斷來隱式的轉(zhuǎn)換成委托，則可以更加精簡:

  <PropertyGroup>
    <TargetFramework>net6.0</TargetFramework>
    <LangVersion>preview</LangVersion>
  </PropertyGroup>

當(dāng)然僅僅是這樣，是無法用于生產(chǎn)的，畢竟不可能所有的業(yè)務(wù)單元我們?nèi)M(jìn)這么一個小小的表達(dá)式里。不過借助WebApplication我們可以打造一個輕量級的系統(tǒng)，可以滿足基本的依賴注入的小型服務(wù)。比如通過自定義特性類型，在啟動階段告知系統(tǒng)為哪些服務(wù)注入哪些訪問路徑，形成路由鍵和終結(jié)點。具體代碼如下：

首先我們創(chuàng)建一個簡易的特性類，只包含httpmethod和path:

[AttributeUsage(AttributeTargets.Method)]
    public class WebRouter : Attribute
    {
        public string path;
        public HttpMethod httpMethod;
        public WebRouter(string path)
        {
            this.path = path;
            this.httpMethod = HttpMethod.Post;
        }
        public WebRouter(string path, HttpMethod httpMethod)
        {
            this.path = path;
            this.httpMethod = httpMethod;
        }
    }

接著我們按照一般的分層設(shè)計一套DEMO應(yīng)用層/倉儲服務(wù)：

public interface IMyService
    {
        Task<MyOutput> Hello(MyInput input);
    }
    public interface IMyRepository
    {
        Task<bool> SaveData(MyOutput data);
    }
    public class MyService : IMyService
    {
        private readonly IMyRepository myRepository;
        public MyService(IMyRepository myRepository)
        {
            this.myRepository = myRepository;
        }
        [WebRouter("/", HttpMethod.Post)]
        public async Task<MyOutput> Hello(MyInput input)
        {
            var result = new MyOutput() { Words = $"hello {input.Name ?? "nobody"}" };
            await myRepository.SaveData(result);
            return await Task.FromResult(result);
        }
    }
    public class MyRepository : IMyRepository
    {
        public async Task<bool> SaveData(MyOutput data)
        {
            Console.WriteLine($"保存成功:{data.Words}");
            return await Task.FromResult(true);
        }
    }

最后我們需要將我們的服務(wù)接入到WebApplication的map里，怎么做呢?首先我們需要定義一套代理類型用來反射并獲取到具體的服務(wù)類型。這里為了簡單的演示，我只設(shè)計包含一個入?yún)⒑蜎]有入?yún)⒌那闆r下：

public abstract class DynamicPorxy
    {
        public abstract Delegate Instance { get; set; }
    }
    public class DynamicPorxyImpl<Tsvc, Timpl, Tinput, Toutput> : DynamicPorxy where Timpl : class where Tinput : class where Toutput : class
    {
        public override Delegate Instance { get; set; }
        public DynamicPorxyImpl(MethodInfo method)
        {
            Instance = ([FromServices] IServiceProvider sp, Tinput input) => ExpressionTool.CreateMethodDelegate<Timpl, Tinput, Toutput>(method)(sp.GetService(typeof(Tsvc)) as Timpl, input);
        }
    }
    public class DynamicPorxyImpl<Tsvc, Timpl, Toutput> : DynamicPorxy where Timpl : class where Toutput : class
    {
        public override Delegate Instance { get; set; }
        public DynamicPorxyImpl(MethodInfo method)
        {
            Instance = ([FromServices] IServiceProvider sp) => ExpressionTool.CreateMethodDelegate<Timpl, Toutput>(method)(sp.GetService(typeof(Tsvc)) as Timpl);
        }
    }

接著我們創(chuàng)建一個代理工廠用于創(chuàng)建服務(wù)的方法委托并創(chuàng)建代理類型實例返回給調(diào)用端

public class DynamicPorxyFactory
    {
        public static IEnumerable<(WebRouter, DynamicPorxy)> RegisterDynamicPorxy()
        {
            foreach (var methodinfo in DependencyContext.Default.CompileLibraries.Where(x => !x.Serviceable && x.Type != "package")
                .Select(x => AssemblyLoadContext.Default.LoadFromAssemblyName(new AssemblyName(x.Name)))
                .SelectMany(x => x.GetTypes().Where(x => !x.IsInterface && x.GetInterfaces().Any()).SelectMany(x => x.GetMethods().Where(y => y.CustomAttributes.Any(z => z.AttributeType == typeof(WebRouter))))))
            {
                var webRouter = methodinfo.GetCustomAttributes(typeof(WebRouter), false).FirstOrDefault() as WebRouter;
                DynamicPorxy dynamicPorxy;
                if (methodinfo.GetParameters().Any())
                    dynamicPorxy = Activator.CreateInstance(typeof(DynamicPorxyImpl<,,,>).MakeGenericType(methodinfo.DeclaringType.GetInterfaces()[0], methodinfo.DeclaringType, methodinfo.GetParameters()[0].ParameterType , methodinfo.ReturnType), new object[] { methodinfo }) as DynamicPorxy;
                else
                    dynamicPorxy = Activator.CreateInstance(typeof(DynamicPorxyImpl<,,>).MakeGenericType(methodinfo.DeclaringType.GetInterfaces()[0], methodinfo.DeclaringType,  methodinfo.ReturnType), new object[] { methodinfo }) as DynamicPorxy;
                yield return (webRouter, dynamicPorxy);
            }
        }
    }
internal class ExpressionTool
    {
        internal static Func<TObj, Tin, Tout> CreateMethodDelegate<TObj, Tin, Tout>(MethodInfo method)
        {
            var mParameter = Expression.Parameter(typeof(TObj), "m");
            var pParameter = Expression.Parameter(typeof(Tin), "p");
            var mcExpression = Expression.Call(mParameter, method, Expression.Convert(pParameter, typeof(Tin)));
            var reExpression = Expression.Convert(mcExpression, typeof(Tout));
            return Expression.Lambda<Func<TObj, Tin, Tout>>(reExpression, mParameter, pParameter).Compile();
        }
        internal static Func<TObj, Tout> CreateMethodDelegate<TObj, Tout>(MethodInfo method)
        {
            var mParameter = Expression.Parameter(typeof(TObj), "m");
            var mcExpression = Expression.Call(mParameter, method);
            var reExpression = Expression.Convert(mcExpression, typeof(Tout));
            return Expression.Lambda<Func<TObj, Tout>>(reExpression, mParameter).Compile();
        }
    }

最后我們創(chuàng)建WebApplication的擴(kuò)展方法來調(diào)用代理工廠以及注入IOC容器：

public static class WebApplicationBuilderExtension
    {
        static Func<string, Delegate, IEndpointConventionBuilder> GetWebApplicationMap(HttpMethod httpMethod, WebApplication webApplication) => (httpMethod) switch
                {
                    (HttpMethod.Get) => webApplication.MapGet,
                    (HttpMethod.Post) => webApplication.MapPost,
                    (HttpMethod.Put) => webApplication.MapPut,
                    (HttpMethod.Delete) => webApplication.MapDelete,
                    _ => webApplication.MapGet
                };
        public static WebApplication RegisterDependencyAndMapDelegate(this WebApplicationBuilder webApplicationBuilder, Action<IServiceCollection> registerDependencyAction, Func<IEnumerable<(WebRouter webRouter, DynamicPorxy dynamicPorxy)>> mapProxyBuilder)
        {
            webApplicationBuilder.Host.ConfigureServices((ctx, services) =>
            {
                registerDependencyAction(services);
            });
            var webApplication = webApplicationBuilder.Build();
            mapProxyBuilder().ToList().ForEach(item => GetWebApplicationMap(item.webRouter.httpMethod, webApplication)(item.webRouter.path, item.dynamicPorxy.Instance));
            return webApplication;
        }
    }

當(dāng)然包括我們的自定義容器注入方法：

public class MyServiceDependency
    {
        public static void Register(IServiceCollection services)
        {
            services.AddScoped<IMyService, MyService>();
            services.AddScoped<IMyRepository, MyRepository>();
        }
    }

最后改造我們的program.cs的代碼，通過擴(kuò)展來注入容器和代理委托并最終生成路由-終結(jié)點：

await WebApplication.CreateBuilder().RegisterDependencyAndMapDelegate(MyServiceDependency.Register,DynamicPorxyFactory.RegisterDynamicPorxy).RunAsync("http://*:80");

這樣這套小型API系統(tǒng)就基本完成了，可以滿足日常的依賴注入和獨立的業(yè)務(wù)單元類型編寫，最后我們啟動并調(diào)用一下，可以看到確實否符合我們的預(yù)期成功的調(diào)用到了應(yīng)用服務(wù)并且倉儲也被正確的執(zhí)行了：

原文鏈接：https://www.cnblogs.com/gmmy/p/14990077.html

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