c# - HttpClientFactory BadRequest？

Question

我需要使用 HttpClientFactory 来连接到外部 api。Startup.cs 中的代码如下所示

public void SetUpHttpClients(IServiceCollection services)
{
        var loginEndpoint = Path.Combine(baseApi, "api/authentication);
        var fileExists = File.Exists(certificatePath);

        if (!fileExists)
            throw new ArgumentException(certificatePath);

        var certificate = new X509Certificate2(certificatePath, certPwd);

        services.AddHttpClient("TestClient", client =>
        {
        client.BaseAddress = new Uri(baseApi);
        client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue(accept));
        client.DefaultRequestHeaders.Add("ApiKey", apiKey);

        var body = new { Username = username, Password = password };
        var jsonBody = JsonConvert.SerializeObject(body);
        var content = new StringContent(jsonBody, Encoding.UTF8, contentType);

        var loginResponse = client.PostAsync(loginEndpoint, content).Result;

        }).ConfigurePrimaryHttpMessageHandler(() =>
        {
            var cookieContainer = new CookieContainer();
            var handler = new HttpClientHandler
            {
                CookieContainer = cookieContainer
            };
            handler.ClientCertificates.Add(certificate);
            return handler;
}); 

我已经使用 HttpClientFactory 在 MessageController 中添加了这段代码，

public class MessagesController : Controller
{
    private readonly IHttpClientFactory _httpClientFactory;

    public ValuesController(IHttpClientFactory httpClientFactory)
    {
        _httpClientFactory = httpClientFactory;
    }

   [HttpGet]
    public IActionResult GetMessages()
    {
        var client = _httpClientFactory.CreateClient("TestClient");
        var result = client.GetStringAsync("/api/messages");
        return Ok(result);
    }
}

但是当我尝试连接并从 HttpClientFactory 获取消息时，出现此错误:

Failed to load resource: net::ERR_CONNECTION_RESET, 404 - BadRequest

Answer 1

您尝试在完成工厂配置之前发出请求，该帖子将失败，因为您在尝试使用客户端的同时仍在配置它。

此处假设 SetUpHttpClients 在 ConfigureServices 中被调用。

public void ConfigureServices(IServiceCollection services) {
    //...

    SetUpHttpClients(services);

    //...

    services.AddMvc();
}

public void SetUpHttpClients(IServiceCollection services) {
    var basePath = Directory.GetCurrentDirectory();
    var certificatePath = Path.Combine(basePath, certPath);
    var fileExists = File.Exists(certificatePath);

    if (!fileExists)
        throw new ArgumentException(certificatePath);

    var certificate = new X509Certificate2(certificatePath, certPwd);

    //Adding a named client
    services.AddHttpClient("TestClient", client => {
        client.BaseAddress = new Uri(baseApi);
        client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue(accept));
        client.DefaultRequestHeaders.Add("ApiKey", apiKey);
    })
    .ConfigurePrimaryHttpMessageHandler(() => {
        var cookieContainer = new CookieContainer();
        var handler = new HttpClientHandler {
            CookieContainer = cookieContainer
        };
        handler.ClientCertificates.Add(certificate);
        return handler;
    });
}

完成配置后，可以根据需要将工厂注入(inject)到 Controller 或服务类中。

以下示例显示了将工厂用作 Controller 的依赖项。

[Route("api/[controller]")]
public class ValuesController : Controller {
    private readonly IHttpClientFactory factory;

    public MyController(IHttpClientFactory factory) {
        this.factory = factory;
    }

    [HttpGet]
    public async Task<IActionResult> Get() {
        var client = factory.CreateClient("TestClient");
        var result = client.GetStringAsync("api/messages");
        return Ok(result);
    }
}

在上面，工厂用于创建指定客户端的实例。它将具有启动期间设置的所有配置，其中包括带有证书的客户端处理程序。

为了能够在启动期间使用客户端(我不建议这样做)，您首先需要将服务集合构建到服务提供者中。

var serviceProvider = services.BuildServiceProvider();
var factory = serviceProvider.GetService<IHttpClientFactory>();
var client = factory.CreateClient("TestClient");

var body = new { Username = username, Password = password };
var jsonBody = JsonConvert.SerializeObject(body);
var content = new StringContent(jsonBody, Encoding.UTF8, contentType);

var loginResponse = client.PostAsync("api/authentication", content).Result;

//...do something with the response

然而，这可能会产生无法预料的结果，因为在启动过程的这个阶段服务集合不会被完全填充。