c# - DelegatingHandler 解压缩 WebApi 中的传入请求

Question

在我的应用程序中，我们从客户端发送大小适中的数据包并接收大小适中的响应，因此我想在向上和返回的过程中实现一些压缩。

在回来的路上它很好，因为我可以依靠 IIS 的动态压缩来为我做这件事，但在回来的路上我发现了以下问题。

我有一个委托(delegate)处理程序，用于解压传入的请求: (此代码的大部分基于 Fabrik.Common ( https://github.com/benfoster/Fabrik.Common ) 的部分内容)

public class DecompressionHandler : DelegatingHandler
{
    public Collection<ICompressor> Compressors;

    public DecompressionHandler()
    {
        Compressors = new Collection<ICompressor> {new GZipCompressor(), new DeflateCompressor()};
    }

    protected async override Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, System.Threading.CancellationToken cancellationToken)
    {
        if (request.Content.Headers.ContentEncoding.IsntNullOrEmpty() && request.Content != null)
        {
            var encoding = request.Content.Headers.ContentEncoding.First();

            var compressor = Compressors.FirstOrDefault(c => c.EncodingType.Equals(encoding, StringComparison.InvariantCultureIgnoreCase));

            if (compressor != null)
            {
                request.Content = await DecompressContentAsync(request.Content, compressor).ConfigureAwait(true);
            }
        }

        var response = await base.SendAsync(request, cancellationToken).ConfigureAwait(true);

        return response;
    }

    private static async Task<HttpContent> DecompressContentAsync(HttpContent compressedContent, ICompressor compressor)
    {
        using (compressedContent)
        {
            var decompressed = new MemoryStream();
            await compressor.Decompress(await compressedContent.ReadAsStreamAsync(), decompressed).ConfigureAwait(true);

            // set position back to 0 so it can be read again
            decompressed.Position = 0;

            var newContent = new StreamContent(decompressed);
            // copy content type so we know how to load correct formatter
            newContent.Headers.ContentType = compressedContent.Headers.ContentType;
            return newContent;
        }
    }
}

public class DeflateCompressor : Compressor
{
    private const string DeflateEncoding = "deflate";

    public override string EncodingType
    {
        get { return DeflateEncoding; }
    }

    public override Stream CreateCompressionStream(Stream output)
    {
        return new DeflateStream(output, CompressionMode.Compress, leaveOpen: true);
    }

    public override Stream CreateDecompressionStream(Stream input)
    {
        return new DeflateStream(input, CompressionMode.Decompress, leaveOpen: true);
    }
}
public abstract class Compressor : ICompressor
{
    public abstract string EncodingType { get; }
    public abstract Stream CreateCompressionStream(Stream output);
    public abstract Stream CreateDecompressionStream(Stream input);

    public virtual Task Compress(Stream source, Stream destination)
    {
        var compressed = CreateCompressionStream(destination);

        return Pump(source, compressed)
            .ContinueWith(task => compressed.Dispose());
    }

    public virtual Task Decompress(Stream source, Stream destination)
    {
        var decompressed = CreateDecompressionStream(source);

        return Pump(decompressed, destination)
            .ContinueWith(task => decompressed.Dispose());
    }

    protected virtual Task Pump(Stream input, Stream output)
    {
        return input.CopyToAsync(output);
    }
}

public interface ICompressor
{
    string EncodingType { get; }
    Task Compress(Stream source, Stream destination);
    Task Decompress(Stream source, Stream destination);
}

public class GZipCompressor : Compressor
{
    private const string GZipEncoding = "gzip";

    public override string EncodingType
    {
        get { return GZipEncoding; }
    }

    public override Stream CreateCompressionStream(Stream output)
    {
        return new GZipStream(output, CompressionMode.Compress, leaveOpen: true);
    }

    public override Stream CreateDecompressionStream(Stream input)
    {
        return new GZipStream(input, CompressionMode.Decompress, leaveOpen: true);
    }
}

解压工作正常，我有我的 request.Content 填充结果是我的解压 JSON。

当我将它传递给 base.SendAsync 并且它到达我的 Controller 方法时，模型为空，而在我实现压缩之前它一切正常。

我读过，当你读取进来的内容流时，这是一次性的事情，但我认为将 request.content 设置为解压后的结果应该让它被再次读取？

Answer 1

我解决了这个问题。

这是我的 HTTPClient 实现中的一个错误，我已经从使用 PostAsJsonAsync 转移到 PostAsync 来执行压缩客户端，但没有添加 Content-Type header 来指定 application/json。

在客户端完成后，一切都按计划进行。