如何从第二个 API 调用返回相同的状态码

Question

我有一个 ASP.NET Core API 调用第二个 API。

如果第二个 API 出现错误，我会在我的服务层抛出异常：

var response = await httpClient.SendAsync(request); //call second API

if (!response.IsSuccessStatusCode)
{
    //return HTTP response with StatusCode = X, if response.StatusCode == X
    throw new HttpRequestException(await response.Content.ReadAsStringAsync()); 
    //this always returns 400
}

如何引发异常，该异常将返回第二个 API 调用的状态码相同的响应？

如果我使用HttpRequestException，它将始终返回 400，即使 response 对象具有 StatusCode = 500。

编辑： 第一个 API 端点如下所示：

            public async Task<ActionResult<HttpResponseMessage>> CreateTenancy([FromBody]TenancyRequest tenancy)
            {
                //Make some calls...
                return Created(string.Empty, new { TenancyID = newTenancyExternalId });
            }

第二个 API 端点如下所示：

    [HttpPost]
    public IHttpActionResult CreateTenancy([FromBody]TenancyDTO tenancyDTO)
    {    
        var tenancy = GetTenancy();    
        return Created(string.Empty, tenancy);
    }

我尝试过使用throw new HttpResponseException(response);，但这会删除描述性异常消息，有效负载最终如下：

{
    "Code": 500,
    "CorrelationId": "2df08016-e5e3-434a-9136-6824495ed907",
    "DateUtc": "2020-01-30T02:02:48.4428978Z",
    "ErrorMessage": "Processing of the HTTP request resulted in an exception. Please see the HTTP response returned by the 'Response' property of this exception for details.",
    "ErrorType": "InternalServerError"
}

我想将ErrorMessage 值保留在原始有效负载中：

{
    "Code": 400,
    "CorrelationId": "ff9466b4-8c80-4dab-b5d7-9bba1355a567",
    "DateUtc": "2020-01-30T03:05:13.2397543Z",
    "ErrorMessage": "\"Specified cast is not valid.\"",
    "ErrorType": "BadRequest"
}

最终目标是返回：

{
    "Code": 500,
    "CorrelationId": "ff9466b4-8c80-4dab-b5d7-9bba1355a567",
    "DateUtc": "2020-01-30T03:05:13.2397543Z",
    "ErrorMessage": "\"Specified cast is not valid.\"",
    "ErrorType": "InternalServerError"
}

Answer 1

您可以简单地进行 API 调用并将其响应代码复制到与 IStatusCodeActionResult 兼容的内容中。

抛出自定义异常的替代方法。创建类似的东西

public class ApiCallException : Exception
{
    public APiCallException(int statusCode, ...)
    {
        ApiStatusCode = statusCode;
    }

    int ApiStatusCode { get; }
    ...
}

并从您的 API 结果中复制状态代码，然后抛出异常。

var response = await httpClient.SendAsync(request); //call second API
if (!response.IsSuccessStatusCode)
{   
    var content = await response.Content.ReadAsStringAsync();
    throw new ApiCallException(500, content); 
}

然后您可以注册一个异常过滤器来处理调用AddMvc时的结果。

services.AddMvc(options => options.Filters.Add<ExceptionFilter>());

ExceptionFilter 可能类似于

public class ExceptionFilter : IExceptionFilter
{
    // ...

    public void OnException(ExceptionContext context)
    {
        if (context.Exception is ApiCallException ace)
        {
            var returnObject = CreateReturnObjectSomehow();
            context.Result = new ObjectResult(returnObject) { StatusCode = ace.StatusCode };
        }
        else
        {
            // do something else
        }
    }
}

Answer 2

我尝试了一些简单的方法，例如更改 API 端点的返回类型并在出现错误时返回对象。否则，构建您自己的 HttpResponseMessage 并返回它。下面的这个 sn-p 使用文本，但如果有的话，您可以使用序列化程序来序列化其他内容。

public async Task<HttpResponseMessage> Test(string str)
{
    var httpClient = new HttpClient();
    var request = new HttpRequestMessage(HttpMethod.Get, $"myAPI that returns different errors 400, 404, 500 etc based on str");

    var response = await httpClient.SendAsync(request);
    if (!response.IsSuccessStatusCode)
        return response;

    // do something else
    return new HttpResponseMessage(System.Net.HttpStatusCode.OK) { Content = new StringContent("Your Text here") };
}

---

使用过滤器的其他方法

使用 IHttpActionResult 作为返回类型的另一种方法，您可以使用过滤器将所有 HttpResponseMessages 符合 IHttpActionResult。

过滤器：创建一个单独的cs文件并使用这个过滤器定义。

public class CustomObjectResponse : IHttpActionResult
{
    private readonly object _obj;

    public CustomObjectResponse(object obj)
    {
        _obj = obj;
    }

    public Task<HttpResponseMessage> ExecuteAsync(CancellationToken cancellationToken)
    {
        HttpResponseMessage response = _obj as HttpResponseMessage;
        return Task.FromResult(response);
    }
}

在你的 API 中，你会像这样使用你的过滤器，

public async Task<IHttpActionResult> Test(string str)
{
    var httpClient = new HttpClient();
    var request = new HttpRequestMessage(HttpMethod.Get, $"http://localhost:4500/api/capacity/update-mnemonics/?mnemonic_to_update={str}");

    var response = await httpClient.SendAsync(request);
    if (!response.IsSuccessStatusCode)
        return new CustomObjectResponse(response);

    // Other Code here

    // Return Other objects 
    KeyValuePair<string, string> testClass = new KeyValuePair<string, string>("Sheldon", "Cooper" );
    return new OkWithObjectResult(testClass);

    // Or Return Standard HttpResponseMessage
    return Ok();

}

Answer 3

感谢 Jawad 和 Kit 提供了很好的答案，帮助我制定了以下解决方案：

原来有一些中间件处理异常：

    public async Task Invoke(HttpContext httpContext)
    {
        try
        {
            await _next(httpContext);
        }
        catch (Exception exception)
        {
            if (httpContext.Response.HasStarted) throw;

            var statusCode = ConvertExceptionToHttpStatusCode(exception);

            httpContext.Response.Clear();
            httpContext.Response.StatusCode = (int)statusCode;
            httpContext.Response.ContentType = "application/json";

            if (statusCode != HttpStatusCode.BadRequest)
            {
                _logger.Error(exception, "API Error");
            }

            await httpContext.Response.WriteAsync(JsonConvert.SerializeObject(new Error(statusCode, httpContext.Request.CorrelationId(), exception.Message, statusCode.ToString())));
        }
    }

Error 类如下所示：

    public class Error
    {
        public int Code { get; }
        public Guid? CorrelationId { get; }
        public DateTime DateUtc { get; }
        public string ErrorMessage { get; }
        public string ErrorType { get; }

        public Error(HttpStatusCode code, Guid? correlationId, string errorMessage, string errorType)
        {
            Code = (int)code;
            CorrelationId = correlationId;
            DateUtc = DateTime.UtcNow;
            ErrorMessage = errorMessage;
            ErrorType = errorType;
        }
    }

我创建了这个类：

public class ApiCallException : Exception
{
    public int StatusCode { get; }
    public override string Message { get; }
    public ApiCallException(int statusCode, string message)
    {
        StatusCode = statusCode;
        Message = message;
    }
}

然后更新了我的原始代码：

                if (!response.IsSuccessStatusCode)
                {
                    throw new ApiCallException((int)response.StatusCode, await response.Content.ReadAsStringAsync());
                }