如何在依赖注入中注入 HttpClient CustomDelegatingHandler答案

【问题标题】：How to inject an HttpClient CustomDelegatingHandler in dependency injection如何在依赖注入中注入 HttpClient CustomDelegatingHandler
【发布时间】：2023-02-24 16:31:27
【问题描述】：

我有一个用于记录目的的自定义委托处理程序：

    public class LoggingDelegatingHandler : DelegatingHandler {

        protected override async Task<HttpResponseMessage> SendAsync(
            HttpRequestMessage request, CancellationToken cancellationToken)
        {
            //my logging
            return await base.SendAsync(request, cancellationToken);
        }
    }

我一直在尝试像这样在我的依赖注入中注入它：

        services.AddHttpClient(nameof(MyAuthorityClient),
                c => { c.BaseAddress = new Uri(myOptions.BaseUri); })
            .AddTransientHttpErrorPolicy(x =>
                x.WaitAndRetryAsync(3, retryAttempt => TimeSpan.FromSeconds(retryAttempt)))
            .ConfigurePrimaryHttpMessageHandler<MyClientHttpHandler>()
            .AddHttpMessageHandler<LoggingDelegatingHandler>();

好像可以编译。但是当执行命中这段代码时：

ar response = await client.GetAsync("/my/api/path");

调试器永远不会到达我的LoggingDelegatingHandler 中的SendAsync 方法。

起初，我以为是因为我正在调用GetAsync，而我的重写方法是SendAsync，但后来我读到它应该仍然命中SendAsync。

我究竟做错了什么？

【问题讨论】：

标签： c# .net

【解决方案1】：

试试下面的代码：

通过创建一个派生自 DelegatingHandler 并覆盖其 SendAsync 方法的新类来定义您的自定义委托处理程序

 public class AuthHeaderHandler : DelegatingHandler
 {
     private readonly string _authToken;

     public AuthHeaderHandler(string authToken)
     {
         _authToken = authToken;
     }

     protected override async Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
     {
         request.Headers.Authorization = new AuthenticationHeaderValue("Bearer", _authToken);
         return await base.SendAsync(request, cancellationToken);
     }
 }

接下来，在服务集合中注册 HttpClient 及其关联的委托处理程序。您可以在启动类的 ConfigureServices 方法中执行此操作。

 public void ConfigureServices(IServiceCollection services)
 {
     // Register the AuthHeaderHandler with the service collection
     services.AddTransient<AuthHeaderHandler>(sp => new AuthHeaderHandler(Configuration["AuthToken"]));

     // Register the HttpClient with the AuthHeaderHandler
     services.AddHttpClient("MyHttpClient").AddHttpMessageHandler<AuthHeaderHandler>();

     // Add other services and dependencies as needed...
  }

使用构造函数注入将 HttpClient 注入到您的类或服务中。

public class MyController : Controller
{
    private readonly HttpClient _httpClient;
    public MyController(IHttpClientFactory httpClientFactory)
    {
        _httpClient = httpClientFactory.CreateClient("MyHttpClient");
    }

    // Use the _httpClient instance to send HTTP requests...
}

【讨论】：