Java.Net.ProtocolException：“意外的状态行：<html>”通过 httpclient 进行连续 api 调用答案

【问题标题】：Java.Net.ProtocolException: 'Unexpected status line: <html>' on consecutive api call through httpclientJava.Net.ProtocolException：“意外的状态行：<html>”通过 httpclient 进行连续 api 调用
【发布时间】：2021-10-04 12:47:10
【问题描述】：

我有一个视图，其中列出了与当前登录用户相关的预订。一旦用户单击其中一个预订，他就会导航到详细信息视图，该视图通过 httpclient 连接到 api 并获取预订详细信息。代码如下。

                client.BaseAddress = new Uri(this.URL);
                client.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Bearer", token.TokenStr);

                var result = await client.GetAsync($"/api/reservation/getforid?Id={id}");
                client.Dispose();
                if (result.StatusCode == System.Net.HttpStatusCode.OK)
                {
                    var str = result.Content.ReadAsStringAsync().Result.Replace("\\", " ");
                    var model = JsonConvert.DeserializeObject<ReservationModel>(str);

                    return model;
                }

详细信息页面还允许修改所选预订的某些数据，并在成功编辑后关闭视图并重新加载预订数据。

发生的情况是在 client.getAsync() 上引发 Java.Net.ProtocolException。并且在向 api 发出请求时，似乎 httpclient 并没有等待数据，而是得到了一些无法转换为响应对象的错误响应。

总结一下：

首次请求显示预订详情页面时，HttpClient 连接到 api 没有任何问题。
修改预订并尝试重新加载预订数据后，即使发出请求的代码/数据相同，也会引发异常

编辑：

我重构了我的项目，使其使用共享的 HttpClient 实例，并找到了导致问题的代码行。

   private IMvxCommand submit;
        public IMvxCommand Submit
        {
            get
            {
                submit = submit ?? new MvxAsyncCommand(async () =>
                {
                    var validationResult =  validateFields();
                    if (validationResult)
                    {
                        await _personApi.UpdatePerson(Model);
                        _nav.Close(this,true);
                 
                    }
                });
                return submit;
            }
        }

_personApi.UpdatePerson() 方法似乎以某种方式搞砸了。评论后视图关闭，列出人员的 ReservationDetailsView 成功获取数据。但是，当我取消注释该方法时，导航到 ReservationDetailViewModel 时会引发相同的异常...

您可以在下面看到 UpdatePerson 方法：

  public async Task UpdatePerson(PersonModel model)
        {

            var token = GetCurrentToken();

            //client = new HttpClient();
            //   client.BaseAddress = new Uri(this.URL);
            client.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Bearer", token.TokenStr);
            //  client.DefaultRequestHeaders.Add("content-type","application/json");
            var dynamic = new { model.Id, model.Name, model.NumberPhone, model.Pesel, model.Street, model.Email, model.WhoToInfrom, model.PostalCode, model.CityPerson };
            var content = new StringContent(JsonConvert.SerializeObject(dynamic), Encoding.UTF8, "application/json");

            var result = await client.PostAsync($"/api/person/update", content);


        }

编辑 2：

仍然卡在这个问题上，不管我使用 HttpClient 多少次，它都可以正常工作，直到我从 EditPersonViewModel 中的 PersonApi 调用 HttpClient 来更新人员。

任何后续调用实际上都会连接到我的 API（我设置了断点，没有抛出异常），但客户端收到如下响应。它来自哪里？

这是 IIS 记录的错误：

Event code: 3005 
Event message: An unhandled exception has occurred. 
Event time: 30.07.2021 11:14:01 
Event time (UTC): 30.07.2021 09:14:01 
Event ID: 17452691323540639122452734bf1713 
Event sequence: 19 
Event occurrence: 15 
Event detail code: 0 
 
Application information: 
    Application domain: /LM/W3SVC/62/ROOT-4-132720999030559530 
    Trust level: Full 
    Application Virtual Path: / 
    Application Path: D:\www\abc\AbcHoliday\AbcHoliday\ 
    Machine name: SERVER3 
 
Process information: 
    Process ID: 11392 
    Process name: w3wp.exe 
    Account name: IIS APPPOOL\abc.syntio.pl 
 
Exception information: 
    Exception type: TaskCanceledException 
    Exception message: A task was canceled.
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Web.Http.Controllers.ApiControllerActionInvoker.<InvokeActionAsyncCore>d__1.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Web.Http.Controllers.ActionFilterResult.<ExecuteAsync>d__5.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Web.Http.Dispatcher.HttpControllerDispatcher.<SendAsync>d__15.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Web.Http.HttpServer.<SendAsync>d__24.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Web.Http.Owin.HttpMessageHandlerAdapter.<InvokeCore>d__20.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Microsoft.Owin.Security.Infrastructure.AuthenticationMiddleware`1.<Invoke>d__5.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Microsoft.Owin.Host.SystemWeb.IntegratedPipeline.IntegratedPipelineContextStage.<RunApp>d__5.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Microsoft.Owin.Host.SystemWeb.IntegratedPipeline.IntegratedPipelineContext.<DoFinalWork>d__2.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at Microsoft.Owin.Host.SystemWeb.IntegratedPipeline.StageAsyncResult.End(IAsyncResult ar)
   at Microsoft.Owin.Host.SystemWeb.IntegratedPipeline.IntegratedPipelineContext.EndFinalWork(IAsyncResult ar)
   at System.Web.HttpApplication.AsyncEventExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute()
   at System.Web.HttpApplication.ExecuteStepImpl(IExecutionStep step)
   at System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously)

 
 
Request information: 
    Request URL: http://abc.syntio.pl/api/reservation/getforid?Id=6384 
    Request path: /api/reservation/getforid 
    User host address: 10.10.0.1 
    User:  
    Is authenticated: True 
    Authentication Type: JWT 
    Thread account name: IIS APPPOOL\abc.syntio.pl 
 
Thread information: 
    Thread ID: 25 
    Thread account name: IIS APPPOOL\abc.syntio.pl 
    Is impersonating: False 
    Stack trace:    at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Web.Http.Controllers.ApiControllerActionInvoker.<InvokeActionAsyncCore>d__1.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Web.Http.Controllers.ActionFilterResult.<ExecuteAsync>d__5.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Web.Http.Dispatcher.HttpControllerDispatcher.<SendAsync>d__15.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Web.Http.HttpServer.<SendAsync>d__24.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Web.Http.Owin.HttpMessageHandlerAdapter.<InvokeCore>d__20.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Microsoft.Owin.Security.Infrastructure.AuthenticationMiddleware`1.<Invoke>d__5.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Microsoft.Owin.Host.SystemWeb.IntegratedPipeline.IntegratedPipelineContextStage.<RunApp>d__5.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Microsoft.Owin.Host.SystemWeb.IntegratedPipeline.IntegratedPipelineContext.<DoFinalWork>d__2.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at Microsoft.Owin.Host.SystemWeb.IntegratedPipeline.StageAsyncResult.End(IAsyncResult ar)
   at Microsoft.Owin.Host.SystemWeb.IntegratedPipeline.IntegratedPipelineContext.EndFinalWork(IAsyncResult ar)
   at System.Web.HttpApplication.AsyncEventExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute()
   at System.Web.HttpApplication.ExecuteStepImpl(IExecutionStep step)
   at System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously)

【问题讨论】：

你检查过服务器日志，或者用 Postman 或浏览器测试过吗？存在许多关于“意外状态行”的问题，它们似乎指向服务器上的问题
您是否考虑过将 Submit 声明为 IMvxAsyncCommand 而不是 IMvxCommand ？我不认为这是问题的一部分，但这是一种更好的做法，尤其是因为您已经在 lambda 中使用了 async/await。

标签： c# xamarin.forms mvvmcross

【解决方案1】：

您将需要尝试/捕获虚拟机中的 Web API 调用。你不能指望这个电话每次都能成功！您可以在出错时使用缓存的响应。

根据错误描述，听起来您无法正确解析 JSON。您可能需要提供与您的 API 服务器正在使用的设置兼容的自定义 JsonSerializerSettings。如果问题是由于 JSON 序列化/反序列化错误引起的，Newtonsoft 应该发送JsonSerializationException 提供更多信息。

至于 Java 异常，目前 Xamarin.Android 默认使用 AndroidClientHandler。似乎存在一些错误，因为您可以在 .NET Standard/PCL 项目中捕获 Java 异常（从 Java.Lang.* 命名空间抛出的异常）。这是一个糟糕的情况，因为 .NET Standard/PCL 项目不了解 Android。

我建议在使用 MvvmCross 的现代 Xamarin.Android 应用程序中使用以下方法：

在整个应用程序中使用单个 HttpClient 实例。通常最好的方法是使用IHttpClientFactory，但 Xamarin 还没有很好的支持。实例化 HttpClient 的好地方是在您的 MvxAndroidSetup 内。

public class Setup : MvxAndroidSetup<App>
{
  protected override void InitializeFirstChance()
  {
    base.InitializeFirstChance();
    var httpClient = new HttpClient(new BasicAuthenticationDelegatingHandler(new SafeAndroidClientHandler()));

    // TODO: Setup httpClient.DefaultRequestHeaders, etc.

    Mvx.IoCProvider.RegisterSingleton(httpClient);
  }
}

使用SafeAndroidClientHandler 捕获 HttpClient 抛出的 Java.Lang.* 异常，然后重新抛出，然后包装在一个 .NET 友好的异常中。这是我的实现。您可以为 GetAsync 方法覆盖做类似的事情。

public class SafeAndroidClientHandler : AndroidClientHandler
{
    public SafeAndroidClientHandler()
    {
        AutomaticDecompression = System.Net.DecompressionMethods.GZip | System.Net.DecompressionMethods.Deflate;
    }

    protected override async Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
    {
        try
        {
            return await base.SendAsync(request, cancellationToken).ConfigureAwait(false);
        }
        catch (Java.Lang.Exception ex)
        {
            throw new HttpRequestException(ex.Message, ex);
        }
    }
}

现在您可以简单地将HttpClient 注入到 ViewModel、Service 等中，这要归功于 MvvmCross IoC。如果抛出 Java.Lang.* 异常，它现在会在 ViewModel 中被捕获为 HttpRequestException。

【讨论】：

【解决方案2】：

HTTPClient Class 说：

// HttpClient 旨在为每个应用程序实例化一次，而不是每次使用。见备注。

static readonly HttpClient client = new HttpClient();

鉴于：

请勿拨打client.Dispose;
不要在每次调用时都创建 HTTPClient - 创建一次。

【讨论】：

感谢您的指出，我不知道这一点。知道我应该在哪里存储这样的 HttpClient 实例吗？还是任何普通的包装类都可以？
@KamilBrucki - 没关系。在一个简单的应用程序中，我在我的自定义应用程序（或应用程序）子类或独立静态类中收集静态数据。在一个更大的项目中，我会创建一个文件夹，其中包含与 HTTP 相关或与服务器通信相关的所有类。同一个文件夹中的静态类会很好。
您正在使用 MvvmCross，因此将 HttpClient 作为 Android 项目中 MvxAndroidSetup.InitializeFirstChance() 方法中的单例存储在 IoC 容器中。