ABP之动态WebAPI

HttpControllerDescriptor与HttpActionDescriptor

HttpControllerDescriptor封装了某个HttpController类型的元数据，我们可以将它视为某个HttpController类型的描述对象。HttpActionDescriptor也类似。上一篇中说到Abp将ApiControler与Action信息分别封装于DynamicApiControllerInfo，DynamicApiActionInfo。Abp种HttpControllerDescriptor与HttpActionDescriptor有新的实现DynamicHttpControllerDescriptor，DyanamicHttpActionDescriptor。

Action的执行

Action方法的执行最终实现在HttpActionDescriptor的ExecuteAsync方法中。DyanamicHttpActionDescriptor也重写了ExecuteAsync，并且将Action的返回值类型定义为AjaxResponse。

        public override Type ReturnType
        {
            get
            {
                return typeof(AjaxResponse);
            }
        }

        public override System.Threading.Tasks.Task<object> ExecuteAsync(HttpControllerContext controllerContext, System.Collections.Generic.IDictionary<string, object> arguments, System.Threading.CancellationToken cancellationToken)
        {
            return base
                .ExecuteAsync(controllerContext, arguments, cancellationToken)
                .ContinueWith(task =>
                {
                    try
                    {
                        if (task.Result == null)
                        {
                            return new AjaxResponse();
                        }

                        if (task.Result is AjaxResponse)
                        {
                            return task.Result;
                        }
                        
                        return new AjaxResponse(task.Result);
                    }
                    catch (AggregateException ex)
                    {
                        ex.InnerException.ReThrow();
                        throw; // The previous line will throw, but we need this to makes compiler happy
                    }
                });
        }

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IHttpControllerSelector与IHttpActionSelector

在上一篇的开头提到了动态的WebApi的核心之一就是对原有的WebApi服务进行了替换。其中就包括IHttpControllerSelector与IHttpActionSelector，这两个接口的主要功能就是对url进行解析生成相应的HttpControllerDescriptor与HttpControllerDescriptor，并传给WebApi系统，再由WebApi系统去执行Action。

在上一篇中说到Abp将ApiController作DynamicApiControllerInfo缓存于DynamicApiControllerManager中，在DynamicApiControllerManager中有一DynamicApiControllers的静态IDictionary属性。

1	`private` `static` `readonly` `IDictionary<string, DynamicApiControllerInfo> DynamicApiControllers;`

在Abp系统的AbpHttpControllerSelector的中，根据url的解析出相应的服务名在DynamicApiControllerManager查找出DynamicApiControllerInfo.再生成DynamicHttpControllerDescriptor返回。

        public override HttpControllerDescriptor SelectController(HttpRequestMessage request)
        {
            if (request != null)
            {
                var routeData = request.GetRouteData();
                if (routeData != null)
                {
                    string serviceNameWithAction;
                    if (routeData.Values.TryGetValue("serviceNameWithAction", out serviceNameWithAction) && DynamicApiServiceNameHelper.IsValidServiceNameWithAction(serviceNameWithAction))
                    {
                        var serviceName = DynamicApiServiceNameHelper.GetServiceNameInServiceNameWithAction(serviceNameWithAction);
                        var controllerInfo = DynamicApiControllerManager.FindOrNull(serviceName);
                        if (controllerInfo != null)
                        {
                            var controllerDescriptor = new DynamicHttpControllerDescriptor(_configuration, controllerInfo.ServiceName, controllerInfo.Type, controllerInfo.Filters);
                            controllerDescriptor.Properties["__AbpDynamicApiControllerInfo"] = controllerInfo;
                            return controllerDescriptor;
                        }
                    }
                }
            }

            return base.SelectController(request);
        }

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DynamicApiControllerInfo中有IDictionary<string, DynamicApiActionInfo> Actions字典所以获取Action也就十分方便。

Abp的路由

Abp定义了自己的路由格式

    public static class DynamicApiRouteConfig
    {
        /// <summary>
        /// Registers dynamic api controllers
        /// </summary>
        public static void Register()
        {
            //Dynamic Web APIs (with area name)
            GlobalConfiguration.Configuration.Routes.MapHttpRoute(
                name: "AbpDynamicWebApi",
                routeTemplate: "api/services/{*serviceNameWithAction}"
                );
        }
    }

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具体的解析就是：

Api/services/{ServicePrefix}/{ServiceName}/{Action}

在SimpleTaskSystem中一访问所有Tasks的url为

http://localhost:6247/api/services/tasksystem/task/GetTasks

ServicePrefix：服务前缀，由开发者自己定义

如SimpleTaskSystem：

[DependsOn(typeof(AbpWebApiModule))] //We declare depended modules explicitly
publicclassSimpleTaskSystemWebApiModule : AbpModule
{
    publicoverridevoidInitialize()
    {
        //This code is used to register classes to dependency injection system for this assembly using conventions.
        IocManager.RegisterAssemblyByConvention(Assembly.GetExecutingAssembly());
 
        //Creating dynamic Web Api Controllers for application services.
        //Thus, 'web api layer' is created automatically by ABP.
 
        DynamicApiControllerBuilder
            .ForAll<IApplicationService>(Assembly.GetAssembly(typeof(SimpleTaskSystemApplicationModule)), "tasksystem")
            .Build();
    }
}

ServiceName:服务名，由服务接口名解析而成。具体规则在BatchApiControllerBuilder. GetConventionalServiceName中

        public static string GetConventionalServiceName(Type type)
        {
            var typeName = type.Name;

            if (typeName.EndsWith("ApplicationService"))
            {
                typeName = typeName.Substring(0, typeName.Length - "ApplicationService".Length);
            }
            else if (typeName.EndsWith("AppService"))
            {
                typeName = typeName.Substring(0, typeName.Length - "AppService".Length);
            }
            else if (typeName.EndsWith("Service"))
            {
                typeName = typeName.Substring(0, typeName.Length - "Service".Length);
            }

            if (typeName.Length > 1 && typeName.StartsWith("I") && char.IsUpper(typeName, 1))
            {
                typeName = typeName.Substring(1);
            }

            return typeName.ToCamelCase();
        }

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Action:即为方法名

HttpVerb

Apb定义的四种Http访问方式

    [Flags]
    public enum HttpVerb
    {
        /// <summary>
        /// GET
        /// </summary>
        Get,

        /// <summary>
        /// POST
        /// </summary>
        Post,

        /// <summary>
        /// PUT
        /// </summary>
        Put,

        /// <summary>
        /// DELETE
        /// </summary>
        Delete,
    }

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原本作者是定义了HttpVerb的处理方式，即对是通过方法名进行的分析。

    /// <summary>
    /// NOTE: This is not used (as all members are private)
    /// </summary>
    internal static class DynamicApiVerbHelper
    {
        private static HttpVerb GetConventionalVerbForMethodName(string methodName)
        {
            if (methodName.StartsWith("Get"))
            {
                return HttpVerb.Get;
            }

            if (methodName.StartsWith("Update") || methodName.StartsWith("Put"))
            {
                return HttpVerb.Put;
            }

            if (methodName.StartsWith("Delete") || methodName.StartsWith("Remove"))
            {
                return HttpVerb.Delete;
            }

            if (methodName.StartsWith("Create") || methodName.StartsWith("Post"))
            {
                return HttpVerb.Post;
            }

            return GetDefaultHttpVerb();
        }

        private static HttpVerb GetDefaultHttpVerb()
        {
            return HttpVerb.Post;
        }
    }

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但作者好像并不打算这么做，在源代码中我也没有找到别的处理方式。