使用 IHttpClientFactory 设置每个请求的请求标头

Question

我正在使用类型化客户端IHttpClientFactory。像这样：

// Startup.cs
services.AddHttpClient<MyHttpClient>()

// MyHttpClient.cs
public class MyHttpClient
{
    public MyHttpClient(HttpClient client)
    {
        Client = client;
    }

    public HttpClient Client { get; }
}

// MyService.cs
public class MyService {
    public MyService(MyHttpClient httpClient) {}

    public async Task SendRequestAsync(string uri, string accessToken) {
        _httpClient.Client.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Bearer", accessToken);
        await _httpClient.Client.GetAsync(uri);
    }
}

我不确定这是如何运作的。请求标头是仅针对此请求设置，还是针对使用 . 的此实例发出的每个后续请求设置httpClient。如何为每个请求设置标头？

Answer 1

您可以使用DelegatingHandler为将发出的每个请求添加标头HttpClient。

public class HeaderHandler: DelegatingHandler
{
    public HeaderHandler()
    {
    }
    public HeaderHandler(DelegatingHandler innerHandler): base(innerHandler)
    {
    }

    protected async override Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
    {
        request.Headers.Add("CUSTOM-HEADER","CUSTOM HEADER VALUE");
        return await base.SendAsync(request, cancellationToken);
    }
}

}

您使用以下方法注册处理程序：

service.AddTransient<HeaderHandler>()
    .AddHttpClient<MyHttpClient>()
    .AddHttpMessageHandler<HeaderHandler>();