从WebAPI发送大文件。内容长度为0
我正在尝试从一个WebAPI（.NET Core）向另一个WebApi（.Net Core）发送大文件（GB）。
我已经设法发送较小的文件作为Multipart Request的一部分，如上一篇文章所述：link
要发送更大的文件，我需要（我认为）将此文件作为StreamContent发送，但是我在接收请求的API中获取Content length = 0。
即使我发送（测试）较小的文件（10 Mb），也会出现问题。
客户代码：
[HttpPost("UploadFiles")]
public async Task<IActionResult> Post(IFormFile file)
{
var filePath = Path.GetTempFileName();
using (var stream = new FileStream(filePath, FileMode.Create, FileAccess.ReadWrite))
{
await file.CopyToAsync(stream);
using (var formDataContent = new MultipartFormDataContent())
{
using (var httpClient = new HttpClient())
{
formDataContent.Add(CreateFileContent(stream, "myfile.test", "application/octet-stream"));
var response = await httpClient.PostAsync(
"http://localhost:56595/home/upload",
formDataContent);
return Json(response);
}
}
}
}
internal static StreamContent CreateFileContent(Stream stream, string fileName, string contentType)
{
var fileContent = new StreamContent(stream);
fileContent.Headers.ContentDisposition = new System.Net.Http.Headers.ContentDispositionHeaderValue("form-data")
{
Name = "\"file\"",
FileName = "\"" + fileName + "\"",
};
fileContent.Headers.ContentType = new System.Net.Http.Headers.MediaTypeHeaderValue(contentType);
return fileContent;
}
Serverside代码：
[HttpPost]
public ActionResult Upload()
{
IFormFile fileFromRequest = Request.Form.Files.First();
string myFileName = fileFromRequest.Name;
// some code
return Ok();
}
问题出在哪里？
要创建Multipart请求，我使用了以下建议：
1 个答案:
答案 0 :(得分：7)
最后我明白了：
有两个问题：
<强> 1。流指针位置
在客户端代码中，更改此：
await file.CopyToAsync(stream);
到那个：
await file.CopyToAsync(stream);
stream.Position = 0;
问题是来自请求的文件被复制到流并且指针的左侧位置在流的末尾。这就是为什么从客户端发送的请求具有适当长度的流，但实际上当它开始读取它时，它不能（读取0字节）。
<强> 2。在服务器上处理请求的错误方法。
我使用了来自dotnetcoretutorials.com
的代码以下工作代码：
客户方：
[HttpPost("UploadFiles")]
public async Task<IActionResult> Post(IFormFile file)
{
var filePath = Path.GetTempFileName();
using (var stream = new FileStream(filePath, FileMode.Create, FileAccess.ReadWrite))
{
await file.CopyToAsync(stream);
stream.Position = 0;
using (var formDataContent = new MultipartFormDataContent())
{
using (var httpClient = new HttpClient())
{
formDataContent.Add(CreateFileContent(stream, "myfile.test", "application/octet-stream"));
var response = await httpClient.PostAsync(
"http://localhost:56595/home/upload",
formDataContent);
return Json(response);
}
}
}
}
internal static StreamContent CreateFileContent(Stream stream, string fileName, string contentType)
{
var fileContent = new StreamContent(stream);
fileContent.Headers.ContentDisposition = new System.Net.Http.Headers.ContentDispositionHeaderValue("form-data")
{
Name = "\"file\"",
FileName = "\"" + fileName + "\"",
};
fileContent.Headers.ContentType = new System.Net.Http.Headers.MediaTypeHeaderValue(contentType);
return fileContent;
}
服务器端：
控制器：
[HttpPost]
[DisableFormValueModelBinding]
public async Task<IActionResult> Upload()
{
var viewModel = new MyViewModel();
try
{
FormValueProvider formModel;
using (var stream = System.IO.File.Create("c:\\temp\\myfile.temp"))
{
formModel = await Request.StreamFile(stream);
}
var bindingSuccessful = await TryUpdateModelAsync(viewModel, prefix: "",
valueProvider: formModel);
if (!bindingSuccessful)
{
if (!ModelState.IsValid)
{
return BadRequest(ModelState);
}
}
}
catch(Exception exception)
{
throw;
}
return Ok(viewModel);
}
来自控制器的方法的助手类：
public static class MultipartRequestHelper
{
// Content-Type: multipart/form-data; boundary="----WebKitFormBoundarymx2fSWqWSd0OxQqq"
// The spec says 70 characters is a reasonable limit.
public static string GetBoundary(MediaTypeHeaderValue contentType, int lengthLimit)
{
var boundary = HeaderUtilities.RemoveQuotes(contentType.Boundary);
if (string.IsNullOrWhiteSpace(boundary.ToString()))
{
throw new InvalidDataException("Missing content-type boundary.");
}
if (boundary.Length > lengthLimit)
{
throw new InvalidDataException(
$"Multipart boundary length limit {lengthLimit} exceeded.");
}
return boundary.ToString();
}
public static bool IsMultipartContentType(string contentType)
{
return !string.IsNullOrEmpty(contentType)
&& contentType.IndexOf("multipart/", StringComparison.OrdinalIgnoreCase) >= 0;
}
public static bool HasFormDataContentDisposition(ContentDispositionHeaderValue contentDisposition)
{
// Content-Disposition: form-data; name="key";
return contentDisposition != null
&& contentDisposition.DispositionType.Equals("form-data")
&& string.IsNullOrEmpty(contentDisposition.FileName.ToString())
&& string.IsNullOrEmpty(contentDisposition.FileNameStar.ToString());
}
public static bool HasFileContentDisposition(ContentDispositionHeaderValue contentDisposition)
{
// Content-Disposition: form-data; name="myfile1"; filename="Misc 002.jpg"
return contentDisposition != null
&& contentDisposition.DispositionType.Equals("form-data")
&& (!string.IsNullOrEmpty(contentDisposition.FileName.ToString())
|| !string.IsNullOrEmpty(contentDisposition.FileNameStar.ToString()));
}
}
public static class FileStreamingHelper
{
private static readonly FormOptions _defaultFormOptions = new FormOptions();
public static async Task<FormValueProvider> StreamFile(this HttpRequest request, Stream targetStream)
{
if (!MultipartRequestHelper.IsMultipartContentType(request.ContentType))
{
throw new Exception($"Expected a multipart request, but got {request.ContentType}");
}
// Used to accumulate all the form url encoded key value pairs in the
// request.
var formAccumulator = new KeyValueAccumulator();
string targetFilePath = null;
var boundary = MultipartRequestHelper.GetBoundary(
MediaTypeHeaderValue.Parse(request.ContentType),
_defaultFormOptions.MultipartBoundaryLengthLimit);
var reader = new MultipartReader(boundary, request.Body);
var section = await reader.ReadNextSectionAsync();
while (section != null)
{
ContentDispositionHeaderValue contentDisposition;
var hasContentDispositionHeader = ContentDispositionHeaderValue.TryParse(section.ContentDisposition, out contentDisposition);
if (hasContentDispositionHeader)
{
if (MultipartRequestHelper.HasFileContentDisposition(contentDisposition))
{
await section.Body.CopyToAsync(targetStream);
}
else if (MultipartRequestHelper.HasFormDataContentDisposition(contentDisposition))
{
// Content-Disposition: form-data; name="key"
//
// value
// Do not limit the key name length here because the
// multipart headers length limit is already in effect.
var key = HeaderUtilities.RemoveQuotes(contentDisposition.Name);
var encoding = GetEncoding(section);
using (var streamReader = new StreamReader(
section.Body,
encoding,
detectEncodingFromByteOrderMarks: true,
bufferSize: 1024,
leaveOpen: true))
{
// The value length limit is enforced by MultipartBodyLengthLimit
var value = await streamReader.ReadToEndAsync();
if (String.Equals(value, "undefined", StringComparison.OrdinalIgnoreCase))
{
value = String.Empty;
}
formAccumulator.Append(key.ToString(), value);
if (formAccumulator.ValueCount > _defaultFormOptions.ValueCountLimit)
{
throw new InvalidDataException($"Form key count limit {_defaultFormOptions.ValueCountLimit} exceeded.");
}
}
}
}
// Drains any remaining section body that has not been consumed and
// reads the headers for the next section.
section = await reader.ReadNextSectionAsync();
}
// Bind form data to a model
var formValueProvider = new FormValueProvider(
BindingSource.Form,
new FormCollection(formAccumulator.GetResults()),
CultureInfo.CurrentCulture);
return formValueProvider;
}
private static Encoding GetEncoding(MultipartSection section)
{
MediaTypeHeaderValue mediaType;
var hasMediaTypeHeader = MediaTypeHeaderValue.TryParse(section.ContentType, out mediaType);
// UTF-7 is insecure and should not be honored. UTF-8 will succeed in
// most cases.
if (!hasMediaTypeHeader || Encoding.UTF7.Equals(mediaType.Encoding))
{
return Encoding.UTF8;
}
return mediaType.Encoding;
}
}
[AttributeUsage(AttributeTargets.Class | AttributeTargets.Method)]
public class DisableFormValueModelBindingAttribute : Attribute, IResourceFilter
{
public void OnResourceExecuting(ResourceExecutingContext context)
{
var formValueProviderFactory = context.ValueProviderFactories
.OfType<FormValueProviderFactory>()
.FirstOrDefault();
if (formValueProviderFactory != null)
{
context.ValueProviderFactories.Remove(formValueProviderFactory);
}
var jqueryFormValueProviderFactory = context.ValueProviderFactories
.OfType<JQueryFormValueProviderFactory>()
.FirstOrDefault();
if (jqueryFormValueProviderFactory != null)
{
context.ValueProviderFactories.Remove(jqueryFormValueProviderFactory);
}
}
public void OnResourceExecuted(ResourceExecutedContext context)
{
}
}
其他想法：
-
（在客户端）行：
fileContent.Headers.ContentType = new System.Net.Http.Headers.MediaTypeHeaderValue（contentType）;
。
-
当MediaTypeHeaderValue是其中之一时，
-
（在客户端上）文件被发送：
应用程序/ x-msdownload
应用/ JSON
应用/八位字节流
-
（在服务器端）在服务器端使用
contentDisposition.FileNameStar行，您需要将其更改为contentDisposition.FileNameStar.ToString() -
（在服务器端）对于服务器端使用的代码将使用较小的文件（Mb），但要发送GB文件，我们需要粘贴在答案中的代码。
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