在 ASP.NET Core Web API 中注册一个新的 DelegatingHandler [英] Registering a new DelegatingHandler in ASP.NET Core Web API

问题描述

我想创建一个扩展 DelegatingHandler 的新处理程序，使我能够在到达控制器之前做一些事情.我在各个地方都读到过，我需要从 DelegatingHandler 继承然后像这样覆盖 SendAsync():

public class ApiKeyHandler : DelegatingHandler{受保护的覆盖任务SendAsync(HttpRequestMessage 请求，CancellationToken 取消令牌){//在这里做自定义的东西返回 base.SendAsync(请求，取消令牌)；}}

这一切都很好，但它没有做任何事情，因为我没有在任何地方注册它！同样，我在很多地方都看到我应该在 WebApiConfig.cs 中这样做，但这不是 ASP.NET Core 版本的 Web API 的一部分.我试图在 Startup.cs 文件(Configure()、ConfigureServices() 等)中找到各种类似的东西，但没有找到.

谁能告诉我应该如何注册我的新处理程序?

解决方案

正如在之前的评论中已经提到的，查看 编写自己的中间件

您的 ApiKeyHandler 可以转换为一个中间件类，该类在其构造函数中接收下一个 RequestDelegate 并支持 Invoke 方法，如下所示:

使用 System.Threading.Tasks;使用 Microsoft.AspNetCore.Http;使用 Microsoft.Extensions.Logging；命名空间 MyMiddlewareNamespace {公共类 ApiKeyMiddleware {私有只读 RequestDelegate _next;私有只读 ILogger _logger;私人 IApiKeyService _service;public ApiKeyMiddleware(RequestDelegate next, ILoggerFactory loggerFactory, IApiKeyService service) {_next = 下一个；_logger = loggerFactory.CreateLogger();_service = 服务}公共异步任务调用(HttpContext 上下文){_logger.LogInformation("处理 API 密钥:" + context.Request.Path);//在这里用服务做自定义的东西等待_next.Invoke(上下文)；_logger.LogInformation(已完成处理api密钥.");}}}

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中间件可以利用 UseMiddleware 扩展将服务直接注入到它们的构造函数中，如下面的例子.依赖注入的服务自动填充，并且扩展需要一个 params 参数数组用于非注入参数.

ApiKeyExtensions.cs

public static class ApiKeyExtensions {公共静态 IApplicationBuilder UseApiKey(这个 IApplicationBuilder 构建器){返回 builder.UseMiddleware();}}

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使用扩展方法和关联的中间件类，配置方法变得非常简单易读.

public void Configure(IApplicationBuilder app) {//...其他配置app.UseApiKey();//...其他配置}

I want to create a new Handler that extends DelegatingHandler to enable me to do stuff before getting as far as the controller. I have read in various places that I need need to inherit from DelegatingHandler then overrride SendAsync() like this:

public class ApiKeyHandler : DelegatingHandler
{        
    protected override Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
    {          
        // do custom stuff here

        return base.SendAsync(request, cancellationToken);
    }
}

This is all fine and dandy except it doesn't do anything because I haven't registered it anywhere! Again, I have seen in numerous places that I should do so in WebApiConfig.cs but that is not a part of the ASP.NET Core version of Web API. I have tried to find analogues amoungst the various things in the Startup.cs file (Configure(), ConfigureServices() etc) but no luck.

Can anyone please tell me how I should go about registering my new handler?

解决方案

As already mentioned in previous comment, look into Writing your own middleware

Your ApiKeyHandler can be converted into a middleware class that takes in the next RequestDelegate in its constructor and supports an Invoke method as shown:

using System.Threading.Tasks;
using Microsoft.AspNetCore.Http;
using Microsoft.Extensions.Logging;

namespace MyMiddlewareNamespace {

    public class ApiKeyMiddleware {
        private readonly RequestDelegate _next;
        private readonly ILogger _logger;
        private IApiKeyService _service;

        public ApiKeyMiddleware(RequestDelegate next, ILoggerFactory loggerFactory, IApiKeyService service) {
            _next = next;
            _logger = loggerFactory.CreateLogger<ApiKeyMiddleware>();
            _service = service
        }

        public async Task Invoke(HttpContext context) {
            _logger.LogInformation("Handling API key for: " + context.Request.Path);

            // do custom stuff here with service      

            await _next.Invoke(context);

            _logger.LogInformation("Finished handling api key.");
        }
    }
}

Middleware can take advantage of the UseMiddleware<T> extension to inject services directly into their constructors, as shown in the example below. Dependency injected services are automatically filled, and the extension takes a params array of arguments to be used for non-injected parameters.

ApiKeyExtensions.cs

public static class ApiKeyExtensions {
    public static IApplicationBuilder UseApiKey(this IApplicationBuilder builder) {
        return builder.UseMiddleware<ApiKeyMiddleware>();
    }
}

Using the extension method and associated middleware class, the Configure method becomes very simple and readable.

public void Configure(IApplicationBuilder app) {
    //...other configuration

    app.UseApiKey();

    //...other configuration
}

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