asp.net-core - Asp.Net Core 5 API Web 以 WCF 等流模式上传大文件

Question

我需要在使用 asp .net core 5 制作的网络服务器上以流模式(一次一个)上传一个大文件 (7GB)。

配置服务器端:

public class Program
    {
        public static void Main(string[] args)
        {
            CreateHostBuilder(args).Build().Run();
        }

        public static IHostBuilder CreateHostBuilder(string[] args) =>
            Host.CreateDefaultBuilder(args)
                .ConfigureWebHostDefaults(webBuilder =>
                {
                    webBuilder.UseStartup<Startup>().UseKestrel(options =>
                    {
                        options.Limits.MaxRequestBodySize = long.MaxValue;
                       
                    });
                });
    }

服务器端的 Controller :

[HttpPost]
[RequestFormLimits(MultipartBodyLengthLimit = Int32.MaxValue)]
public async Task PostStream(IFormFile formFiles)
{
    //rest of code
}

客户端(桌面应用)

using (var httpClient = new HttpClient())
                {
                    using (var content = new MultipartFormDataContent())
                    {
                        string fileName = @"D:\largeFile.zip";

                        FileStream fileStream = File.OpenRead(fileName);
                        HttpContent fileStreamContent = new StreamContent(fileStream);

                        fileStreamContent.Headers.ContentDisposition = new ContentDispositionHeaderValue("form-data") { Name = "formFiles", FileName = fileName };
                        fileStreamContent.Headers.ContentType = new MediaTypeHeaderValue("application/octet-stream");

                        content.Add(fileStreamContent);

                       
                        var response = httpClient.PostAsync("http://localhost:5000/weatherforecast", content).Result;
                        response.EnsureSuccessStatusCode();
                }

系统工作到 1 GB，大文件 (7GB) 服务器取消请求，我注意到发送到服务器的文件不是流式传输而是完全上传，我期待在服务器上进行渐进式上传，就像在 WCF 上发生的那样。如何逐步将文件发送到服务器？

Answer 1

因为你的服务器端代码

[HttpPost]
[RequestFormLimits(MultipartBodyLengthLimit = Int32.MaxValue)]
public async Task PostStream(IFormFile formFiles)
{
    //rest of code
}

我假设你没有关注这个 tutorial然而。而且教程中的代码太多了，所以我将总结一下我所做的并在下面给你一个例子。

首先，您需要一个过滤器来禁用模型绑定(bind)。

[AttributeUsage(AttributeTargets.Class | AttributeTargets.Method)]
public class DisableFormValueModelBindingAttribute : Attribute, IResourceFilter
{
    public void OnResourceExecuting(ResourceExecutingContext context)
    {
        if (!RequestHelper.IsMultipartContentType(context.HttpContext.Request.ContentType))
        {
            context.Result = new BadRequestObjectResult("Request is not a 'multipart' request");
        }

        var factories = context.ValueProviderFactories;
        factories.RemoveType<FormValueProviderFactory>();
        factories.RemoveType<FormFileValueProviderFactory>();
        factories.RemoveType<JQueryFormValueProviderFactory>();
    }

    public void OnResourceExecuted(ResourceExecutedContext context)
    {
    }
}

然后是处理上传请求的服务代码。确保稍微更改它以将文件保存到磁盘而不是内存中。

public class MultipartRequestService : IMultipartRequestService
{
    public async Task<(Dictionary<string, StringValues>, byte[])> GetDataFromMultiPart(MultipartReader reader, CancellationToken cancellationToken)
    {
        var formAccumulator = new KeyValueAccumulator();
        var file = new byte[0];

        MultipartSection section;
        while ((section = await reader.ReadNextSectionAsync(cancellationToken)) != null)
        {
            if (!ContentDispositionHeaderValue.TryParse(section.ContentDisposition, out var contentDisposition))
            {
                continue;
            }

            if (contentDisposition.IsFormDisposition())
            {
                formAccumulator = await AccumulateForm(formAccumulator, section, contentDisposition);
            }

            else if (contentDisposition.IsFileDisposition())
            {
                // you will want to replace all of this because it copies the file into a memory stream. We don't want that.
                await using var memoryStream = new MemoryStream();
                await section.Body.CopyToAsync(memoryStream, cancellationToken);

                file = memoryStream.ToArray();
            }
        }

        return (formAccumulator.GetResults(), file);
    }

    private Encoding GetEncoding(MultipartSection section)
    {
        var hasMediaTypeHeader = MediaTypeHeaderValue.TryParse(section.ContentType, out var mediaType);

        // UTF-7 is insecure and shouldn't be honored. UTF-8 succeeds in 
        // most cases.
        if (!hasMediaTypeHeader || Encoding.UTF7.Equals(mediaType.Encoding))
        {
            return Encoding.UTF8;
        }

        return mediaType.Encoding;
    }

    private async Task<KeyValueAccumulator> AccumulateForm(KeyValueAccumulator formAccumulator, MultipartSection section, ContentDispositionHeaderValue contentDisposition)
    {
        var key = HeaderUtilities.RemoveQuotes(contentDisposition.Name).Value;
        using var streamReader = new StreamReader(section.Body, GetEncoding(section), true, 1024, true);
        {
            var value = await streamReader.ReadToEndAsync();
            if (string.Equals(value, "undefined", StringComparison.OrdinalIgnoreCase))
            {
                value = string.Empty;
            }
            formAccumulator.Append(key, value);

            if (formAccumulator.ValueCount > FormReader.DefaultValueCountLimit)
            {
                throw new InvalidDataException($"Form key count limit {FormReader.DefaultValueCountLimit} exceeded.");
            }
        }

        return formAccumulator;
    }
}

最后是 Controller 代码

[HttpPost()]
[DisableFormValueModelBinding]
public async Task<IActionResult> Upload(
    [FromServices] IMultipartRequestService multipartRequestService,
    CancellationToken cancellationToken)
{
    var reader = new MultipartReader(HttpContext.Request.GetMultipartBoundary(), HttpContext.Request.Body)
    {
        BodyLengthLimit = uploadLimit.Value.ChunkSizeLimitInBytes
    };

    _logger.LogInformation("Read data and file from uploaded request");
    var (forms, file) = await multipartRequestService.GetDataFromMultiPart(reader, cancellationToken);

    // do anything you want

    return Ok();
}