HttpClient PostAsync（）不起作用-Java 学习之路

在我的Xamarin Forms App中

我正在尝试将Json字符串发布到我的web服务，当我使用以下代码时，它是RestFul API：

public static async Task<bool> SaveRolAsync(Methods Method, Role Rol)
    {
        try
        {
            HttpClient client = new HttpClient();
            client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));

            var uri = ("http://myservice.com/roles/");
            HttpResponseMessage response = null;

            try
            {
                var jSettings = new JsonSerializerSettings();
                jSettings.NullValueHandling = NullValueHandling.Ignore;
                jSettings.MissingMemberHandling = MissingMemberHandling.Ignore;

                var JsonData = JsonConvert.SerializeObject(Rol);
                var RoleContent = new StringContent(JsonData, Encoding.UTF8, "application/json");

                if (Method == Methods.PUT || Method == Methods.PATCH)
                {
                    response = await client.PutAsync(uri, RoleContent);
                }

                if (Method == Methods.POST)
                {
                    response = await client.PostAsync(uri, RoleContent);
                }

                if (Method == Methods.DELETE)
                {
                    throw new NotImplementedException();
                }

                return response.IsSuccessStatusCode;

            }
            catch (JsonException jse)
            {
                return false;
            }
        }
        catch (Exception ex)
        {
            // Exceptions Throws here
            // @T This line i got The request requires buffering data to succeed
            return false;
        }
    }

抛出异常：

该请求需要缓冲数据才能成功

堆栈跟踪：

{System.Net.WebException：请求需要缓冲数据才能成功 . 在System.Net.HttpWebRequest.EndGetResponse（System.IAsyncResult asyncResult）[0x00064] in：0 at System.Threading.Tasks.TaskFactory1 [TResult] .FromAsyncCoreLogic（System.IAsyncResult iar，System.Func2 [T，TResult] endFunction，System .Action1 [T] endAction，System.Threading.Tasks.Task1 [TResult] promise，System.Boolean requiresSynchronization）[0x00014] in：0 ---从抛出异常的上一个位置的堆栈跟踪结束---在System . Runtime.ExceptionServices.ExceptionDispatchInfo.Throw（）[0x0000c] in：0，System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess（System.Threading.Tasks.Task任务）[0x0004e] in：0，System.Runtime.CompilerServices.TaskAwaiter . HandleNonSuccessAndDebuggerNotification（System.Threading.Tasks.Task任务）[0x0002e] in：0，System.Runtime.CompilerServices.TaskAwaiter.ValidateEnd（System.Threading.Tasks.Task任务）[0x0000b] in：0，System.Runtime.CompilerServices . 在<a中配置了TaskAwaitable1 ConfiguredTaskAwaiter [TResult] .GetResult（）[0x00000] 66f207c1e5949e9a252c01e27bbd34e>：0在System.Net.Http.HttpClientHandler <SendAsync> c__async0.MoveNext（）[0x0041e] in <566d6cf6576345098cb5e08ad43d5e78>：0 ---从抛出异常的上一个位置开始的堆栈跟踪结束---在System.Runtime System.Runtime中的<a66f207c1e5949e9a252c01e27bbd34e>中的System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess（System.Threading.Tasks.Task任务）[0x0004e]中的<a66f207c1e5949e9a252c01e27bbd34e>中的.ExceptionServices.ExceptionDispatchInfo.Throw（）[0x0000c]：0 .CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification（System.Threading.Tasks.Task任务）[0x0002e]在<a66f207c1e5949e9a252c01e27bbd34e>：0中的System.Runtime.CompilerServices.TaskAwaiter.ValidateEnd（System.Threading.Tasks.Task任务）[0x0000b] in < a66f207c1e5949e9a252c01e27bbd34e>：0 at System.Runtime.CompilerServices.ConfiguredTaskAwaitable1 ConfiguredTaskAwaiter [TResult] .GetResult（）[0x00000] in：0 at System.Net.Http.HttpClient c__async0.MoveNext（）[0x000f3] in <566d6cf6576345098cb5e08ad43d5e78>：0 ---从抛出异常的上一个位置开始的堆栈跟踪结束---在System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess上的System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw（）[0x0000c]中：0 （System.Threading.Tasks.Task任务）[0x0004e] in：0：System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification（System.Threading.Tasks.Task task）[0x0002e] in：0 at System.Runtime.CompilerServices.TaskAwaiter .ValidateEnd（System.Threading.Tasks.Task任务）[0x0000b] in：0 at System.Runtime.CompilerServices.TaskAwaiter`1 [TResult] .GetResult（）[0x00000] in：0 at MyAPP.Webservice d _4.MoveNext（） C：\ MyProject \ Classes \ Webservice.cs中的[0x000d0]：140}

还试过：SendAsync（）TyM.Wiśnicki

public static async Task<bool> SaveRolAsync(MediwareLib.Methods Method, Role Rol)
    {
        try
        {
            HttpClient client = new HttpClient();
            client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));

            var uri = (BaseRequestUrl + "roles/");
            HttpResponseMessage response = null;
            var request = new HttpRequestMessage();

            try
            {
                var jSettings = new JsonSerializerSettings();
                jSettings.NullValueHandling = NullValueHandling.Ignore;
                jSettings.MissingMemberHandling = MissingMemberHandling.Ignore;

                var JsonData = JsonConvert.SerializeObject(Rol);

                var RoleContent = new StringContent(JsonData, Encoding.UTF8, "application/json");

                if (Method == MediwareLib.Methods.PUT || Method == MediwareLib.Methods.PATCH)
                {
                    request = new HttpRequestMessage(HttpMethod.Put, uri);
                    request.Content = RoleContent;

                    response = await client.SendAsync(request,
                    HttpCompletionOption.ResponseHeadersRead);
                }

                if (Method == MediwareLib.Methods.POST)
                {
                    request = new HttpRequestMessage(HttpMethod.Post, uri);
                    request.Content = RoleContent;

                    response = await client.SendAsync(request,
                    HttpCompletionOption.ResponseHeadersRead);
                }

                if (Method == MediwareLib.Methods.DELETE)
                {
                    throw new NotImplementedException();
                    // response = await client.DeleteAsync(uri + Rol.Id);
                }

                return response.IsSuccessStatusCode;

            }
            catch (JsonException jse)
            {
                Globals.Log("SaveRolAsync: " + jse.ToString());
                return false;
            }
        }
        catch (Exception ex)
        {
            Globals.Log("SaveRolAsync: " + ex.ToString());
            return false;
        }

    }

enter image description here

2 回答

您可以使用 SendAsync() 而 HttpCompletionOption.ResponseHeadersRead 而不是 PostAsync() ，问题在于读取响应，它在未准备就绪时正在读取 .

var request = new HttpMessageRequest(yourUrl);
request.Content = yourContent;
var response = await client.SendAsync(request, 
HttpCompletionOption.ResponseHeadersRead);

使用 HttpCompletionOption.ResponseHeadersRead

只要有响应并读取 Headers ，操作就应该完成 . 内容尚未阅读 .

Edit 您可以使用 HttpWebRequest 代替 HttpClient

public async Task<string> PostTest(object sampleData, string uri)
    {
        var request = (HttpWebRequest) WebRequest.Create(new Uri(uri));
        request.ContentType = "application/json";
        request.Method = "POST";
        request.Timeout = 4000; //ms
        var itemToSend = JsonConvert.SerializeObject(sampleData);
        using (var streamWriter = new StreamWriter(await request.GetRequestStreamAsync()))
        {
            streamWriter.Write(itemToSend);
            streamWriter.Flush();
            streamWriter.Dispose();
        }

        // Send the request to the server and wait for the response:  
        using (var response = await request.GetResponseAsync())
        {
            // Get a stream representation of the HTTP web response:  
            using (var stream = response.GetResponseStream())
            {
                var reader = new StreamReader(stream);
                var message = reader.ReadToEnd();
                return message;
            }
        }
    }

回复于 2024-04-30T12:01:06+08:00

1
由于您使用的是 .Result 或 .Wait 或 await ，因此最终会导致代码中出现 deadlock .

您可以在 async 方法中使用 ConfigureAwait(false) preventing deadlock

像这样：
```
response = await client.PostAsync(uri, RoleContent).ConfigureAwait(false);
```
您可以尽可能使用ConfigureAwait（false）来阻止异步代码 .
回复于 2024-04-30T12:01:06+08:00

HttpClient PostAsync（）不起作用

2 回答

相关问题