大家好,我是失業在家,正在找工作的博主Jerry。今天給大家介紹一個能大大減少ASP.Net Minimal WebApi編碼量的方法。
我們一般會把微服務的VO和DTO封裝成消息類,並作爲WebApi的Request和Response參數進行網絡傳遞。
如果使用MediatR,我們封裝的消息類就要實現 MediatR Contract 接口 IRequest<> 或者INotification, 例如我的代碼如下:
namespace MediatRApplication.CategoryCRUD { public class CreateCategory : IRequest<CreateCategoryResult> { public string Message { get; set; } } public class CreateCategoryResult { public string Message { get; set; } } public class ReadCategory : IRequest<ReadCategoryResult> { public string Message { get; set; } } public class ReadCategoryResult { public string Message { get; set; } } public class UpdateCategory : IRequest<UpdateCategoryResult> { public string Message { get; set; } } public class UpdateCategoryResult { public string Message { get; set; } } public class DeleteCategory : IRequest { public string Message { get; set; } } }
如上代碼是對Category業務實體進行CRUD操作封裝的DTO消息類,每個消息類都實現了MediatR的IRequest接口。有了消息類,就可以對每個消息類編寫處理器(Handler),以實現業務功能。
有了消息類,就需要爲每個消息類創建WebApi接口,以實現消息的Request和Response。WebAPI接口中沒有業務邏輯,只需要調用MediatR的Send方法將消息類發送給Handler即可。
但是,由於消息類比較多,一個一個創建WebApi接口是一件費時費力,並且容易出錯的事情。作爲一個架構師,是無法忍受程序員們幹這些出力不討好的事情的。
所以,爲了項目,爲了大家的Work Life Banlance, 我把創建WebApi這件事情減少成了一行代碼。是的,你沒看錯,就是隻要一行代碼:
app.MapMediatorWebAPIs(typeof(CreateCategory).Assembly);
只要在ASP.Net Minimal API 項目的Progam文件中加入這一行代碼,就可以把指定程序集中所有實現了IRequest<>和INotification的消息類自動生成WebAPI接口。
看起來很神奇,其實也不神奇。主要就是兩個字:反射。還有泛型。
簡單來說,就是在指定程序集中,通過反射查找那些類實現了IRequest<>或者INotification,然後在通過對泛型映射WebAPI方法的反射調用,爲每個消息類生成WebApi接口。
Let me show you the code:
using MediatR; using MediatRApplication; using Microsoft.AspNetCore.Mvc; using Microsoft.Extensions.Configuration; using Microsoft.Extensions.Logging; using System.Reflection; using System.Xml.Linq; namespace MediatRWebAPI { public static class MediatorWebAPIExtensions { /// <summary> /// 擴展方法,爲所有MediatR Contract 消息類創建WebAPI接口 /// </summary> /// <param name="app"></param> /// <param name="assemblies">Contract 消息類所在程序集</param> /// <returns></returns> public static IEndpointRouteBuilder MapMediatorWebAPIs(this IEndpointRouteBuilder app, params Assembly[] assemblies) { //爲所有實現了IRequest<>的消息類創建WebAPI接口 Type genericRequestType = typeof(IRequest<>); var sendMethodInfo = typeof(MediatorWebAPIExtensions).GetMethod("MapMediatorSendApi", BindingFlags.NonPublic | BindingFlags.Static); foreach (var assembly in assemblies) { //獲取該程序集中所有實現了IRequest<>的消息類類型 var requestTypes = assembly.GetTypes().Where(type => !type.IsInterface && type.GetInterfaces().Any(t => t.IsGenericType && t.GetGenericTypeDefinition() == genericRequestType)); foreach (var requestType in requestTypes) { //獲取IRequest<>中尖括號中的泛型參數類型。 var responseType = requestType.GetInterfaces().First(t => t.IsGenericType && t.GetGenericTypeDefinition() == genericRequestType).GetGenericArguments().First(); //反射調用泛型映射WebApi方法 var genericMethod = sendMethodInfo.MakeGenericMethod(requestType, responseType); genericMethod.Invoke(null, new object[] { app, requestType.Name }); } } //爲所有實現了INotification的消息類創建WebAAPI接口 Type genericNotificationType = typeof(INotification); var publishMethodInfo = typeof(MediatorWebAPIExtensions).GetMethod("MapMediatorPublishApi", BindingFlags.NonPublic | BindingFlags.Static); foreach (var assembly in assemblies) { //獲取該程序集中所有實現了INotification的消息類類型 var requestTypes = assembly.GetTypes().Where(type => !type.IsInterface && genericNotificationType.IsAssignableFrom(type)); foreach (var requestType in requestTypes) { //反射調用泛型映射WebApi方法 var genericMethod = publishMethodInfo.MakeGenericMethod(requestType); genericMethod.Invoke(null, new object[] { app, requestType.Name }); } } return app; } /// <summary> /// 爲實現了IRequest<>的消息類爲映射爲WebAPI接口,根據消息類名稱生成對應的CRUDD Http Method。 /// </summary> /// <typeparam name="TRequest"></typeparam> /// <typeparam name="TResponse"></typeparam> /// <param name="app"></param> /// <param name="requestTypeName"></param> internal static void MapMediatorSendApi<TRequest, TResponse>(IEndpointRouteBuilder app, string requestTypeName) where TRequest : IRequest<TResponse> { if (requestTypeName.StartsWith("Create")) //Http Post { var uri = new Uri(requestTypeName.Replace("Create", ""), UriKind.Relative); app.MapPost(uri.ToString(), async ([FromServices] IMediator mediator, [FromBody] TRequest request) => { TResponse response = await mediator.Send(request); return Results.Created(uri, response); }).WithName(requestTypeName).WithOpenApi(); } else if (requestTypeName.StartsWith("Read")) //Http Get { var uri = new Uri(requestTypeName.Replace("Read", ""), UriKind.Relative); app.MapGet(uri.ToString(), async ([FromServices] IMediator mediator, [FromBody] TRequest request) => { TResponse response = await mediator.Send(request); return Results.Ok(response); }).WithName(requestTypeName).WithOpenApi(); } else if (requestTypeName.StartsWith("Update")) //Http Put { var uri = new Uri(requestTypeName.Replace("Update", ""), UriKind.Relative); app.MapPut(uri.ToString(), async ([FromServices] IMediator mediator, [FromBody] TRequest request) => { TResponse response = await mediator.Send(request); return Results.Ok(response); }).WithName(requestTypeName).WithOpenApi(); } else if (requestTypeName.StartsWith("Delete")) //Http Delete { var uri = new Uri(requestTypeName.Replace("Delete", ""), UriKind.Relative); app.MapDelete(uri.ToString(), async ([FromServices] IMediator mediator, [FromBody] TRequest request) => { TResponse response = await mediator.Send(request); return Results.NoContent(); }).WithName(requestTypeName).WithOpenApi(); } else //如不匹配則生成MediatR Send WebAPI接口 { app.MapPost("/mediatr/send/" + requestTypeName, async ([FromServices] IMediator mediator, [FromBody] TRequest request) => { TResponse response = await mediator.Send(request); return Results.Ok(response); }).WithName(requestTypeName).WithOpenApi(); } } /// <summary> /// 爲實現了INotification的消息類映射WebAPI接口。 /// </summary> /// <typeparam name="TNotification"></typeparam> /// <param name="app"></param> /// <param name="requestTypeName"></param> internal static void MapMediatorPublishApi<TNotification>(IEndpointRouteBuilder app, string requestTypeName) where TNotification : INotification { app.MapPost("/mediatr/publish/" + requestTypeName, async ([FromServices] IMediator mediator, [FromBody] TNotification notification) => { await mediator.Publish(notification); return Results.Ok(); }).WithName(requestTypeName).WithOpenApi(); } } }
如上就是實現這個功能的所有代碼,爲了讓大家看明白,我加了很多註釋。如果哪位小夥伴還不明白就在下面留言。這些代碼最難的地方就是對於泛型接口的處理。
我的示例項目如下,代碼已經上傳到了GitHub :iamxiaozhuang/MediatRWebAPI (github.com) 大家隨便用。