asp.net core mvc 之 DynamicApi

  这段时间闲赋在家,感觉手痒,故想折腾一些东西.

  由于之前移植了一个c#版本的spring cloud feign客户端(https://github.com/daixinkai/feign.net),所以想弄个配套的服务端动态接口,实现服务即接口的功能.虽然ABP框架内部包含一个功能强大的DynamicWebApi,但是我只是想要一个独立简单的组件,用来实现以下效果:

  有一个业务服务 : 

   public interface ITestService
    {
        Task<string> GetName(int id);
    }

自动生成类似以下的接口

    [Route("api/test")]
    public class TestController : ControllerBase
    {
        public TestController(ITestService testService)
        {
            _testService = testService;
        }

        ITestService _testService;

        [HttpGet("name/{id}")]
        public Task<string> GetName(int id)
        {
            return _testService.GetName(id);
        }

    }

项目地址 : https://github.com/daixinkai/Microsoft.AspNetCore.Mvc.DynamicApi

-------------------------------------------------------------------------------------------------

首先定义一个DynamicApiAttribute,替代RouteAttribute的功能

    [AttributeUsage(AttributeTargets.Interface, AllowMultiple = false, Inherited = true)]
    public class DynamicApiAttribute : Attribute, Microsoft.AspNetCore.Mvc.Routing.IRouteTemplateProvider
    {
        public DynamicApiAttribute() { }
        public DynamicApiAttribute(string template)
        {
            Template = template;
        }
        public string Template { get; set; }public int? Order { get; set; }
        public string Name { get; set; }
    }

思路就是查找标记了DynamicApiAttribute特性的接口,生成一个代理类型注册为控制器

1. BuildProxyType: 定义一个 TypeBuilder

先生成一个类型为当前接口类型的字段 : 

FieldBuilder interfaceInstanceFieldBuilder = typeBuilder.DefineField("_interfaceInstance", interfaceType, FieldAttributes.Private);

生成构造函数,接收一个当前接口类型的对象,并赋值给上述字段

     ConstructorBuilder constructorBuilder = typeBuilder.DefineConstructor(
                MethodAttributes.Public,
                CallingConventions.Standard,
                new Type[] { interfaceType });
            ILGenerator constructorIlGenerator = constructorBuilder.GetILGenerator();
            constructorIlGenerator.Emit(OpCodes.Ldarg_0);
            constructorIlGenerator.Emit(OpCodes.Ldarg_1);
            constructorIlGenerator.Emit(OpCodes.Stfld, interfaceInstanceFieldBuilder);
            constructorIlGenerator.Emit(OpCodes.Ret);

查找接口的所有方法,全部生成

  foreach (var method in interfaceType.GetMethodsIncludingBaseInterfaces())
            {
                BuildMethod(typeBuilder, interfaceType, method, interfaceInstanceFieldBuilder);
            }

        static void BuildMethod(TypeBuilder typeBuilder, Type interfaceType, MethodInfo method, FieldBuilder interfaceInstanceFieldBuilder)
        {
            MethodAttributes methodAttributes =
                    MethodAttributes.Public
                    | MethodAttributes.HideBySig
                    | MethodAttributes.NewSlot
                    | MethodAttributes.Virtual
                    | MethodAttributes.Final;
            var parameters = method.GetParameters();
            Type[] parameterTypes = parameters.Select(s => s.ParameterType).ToArray();
            MethodBuilder methodBuilder = typeBuilder.DefineMethod(method.Name, methodAttributes, CallingConventions.Standard, method.ReturnType, parameterTypes);

            #region parameterName

            for (int i = 0; i < parameters.Length; i++)
            {
                methodBuilder.DefineParameter(i + 1, ParameterAttributes.None, parameters[i].Name);
            }

            #endregion

            typeBuilder.DefineMethodOverride(methodBuilder, method);
            ILGenerator iLGenerator = methodBuilder.GetILGenerator();
            iLGenerator.Emit(OpCodes.Ldarg_0); // this
            iLGenerator.Emit(OpCodes.Ldfld, interfaceInstanceFieldBuilder);
            for (int i = 0; i < parameterTypes.Length; i++)
            {
                iLGenerator.Emit(OpCodes.Ldarg_S, i + 1);
            }
            iLGenerator.Emit(OpCodes.Call, method);
            iLGenerator.Emit(OpCodes.Ret);
            var datas = CustomAttributeData.GetCustomAttributes(method);
            foreach (var data in datas)
            {
                CustomAttributeBuilder customAttributeBuilder = new CustomAttributeBuilder(data.Constructor, data.ConstructorArguments.Select(s => s.Value).ToArray());
                methodBuilder.SetCustomAttribute(customAttributeBuilder);
            }
        }

最后别忘了复制特性 

      var datas = CustomAttributeData.GetCustomAttributes(interfaceType);
            foreach (var data in datas)
            {
                CustomAttributeBuilder customAttributeBuilder = new CustomAttributeBuilder(data.Constructor, data.ConstructorArguments.Select(s => s.Value).ToArray());
                typeBuilder.SetCustomAttribute(customAttributeBuilder);
            }

这样代理类型就生成完毕了

2.注册到Mvc框架中

由于默认ControllerFeatureProvider不支持生成的代理类型,需要自定义实现

    public class DynamicApiControllerFeatureProvider : ControllerFeatureProvider
    {
        protected override bool IsController(TypeInfo typeInfo)
        {
            return typeInfo.IsProxyApi();
        }
    }

       public static IMvcBuilder AddDynamicApi(this IMvcBuilder builder)
        {

            var feature = new ControllerFeature();

            foreach (AssemblyPart assemblyPart in builder.PartManager.ApplicationParts.OfType<AssemblyPart>())
            {
                foreach (var type in assemblyPart.Types)
                {
                    if (type.IsInterface && type.IsDefinedIncludingBaseInterfaces<DynamicApiAttribute>() && !type.IsDefined(typeof(NonDynamicApiAttribute)) && !type.IsGenericType)
                    {
                        feature.Controllers.Add(DynamicApiProxy.GetProxyType(type));//feature.Controllers.Add没什么卵用
                    }
                }
            }

            builder.AddApplicationPart(DynamicApiProxy.DynamicAssembly.AssemblyBuilder);

            builder.PartManager.FeatureProviders.Add(new DynamicApiControllerFeatureProvider());

            
            return builder;
        }

这样就完成了,是不是很简单实用! 另外DynamicApi支持Mvc内置的Filter

3. 测试一下 

    [DynamicApi("api/testService")]
    public interface ITestService
    {
        //[Microsoft.AspNetCore.Authorization.Authorize]
        [HttpGet("name/{id}")]
        Task<string> GetName(int id);
    }

    public class TestService : ITestService
    {
        public Task<string> GetName(int id)
        {
            return Task.FromResult("Name" + id);
        }
    }

最后别忘了注入服务

        public void ConfigureServices(IServiceCollection services)
        {
            services.AddMvc().SetCompatibilityVersion(CompatibilityVersion.Version_2_2).AddDynamicApi();
            services.AddTransient<ITestService, TestService>();
        }

大功告成