如何从S3获取GetObjectResponse的字节？

Question

我正在从Amazon S3检索文件.我想将文件转换为字节,以便我可以按如下方式下载:

var download = new FileContentResult(bytes, "application/pdf");
download.FileDownloadName = filename;
return download;

我有这里的文件:

var client = Amazon.AWSClientFactory.CreateAmazonS3Client(
        accessKey,
        secretKey,
        config
        );
GetObjectRequest request = new GetObjectRequest();
GetObjectResponse response = client.GetObject(request);          

我知道response.WriteResponseStreamToFile()但我想将文件下载到常规下载文件夹.如果我将GetObjectResponse转换为字节,我可以返回该文件.我怎样才能做到这一点？

Answer 1

这是我为其他需要它的人找到的解决方案:

GetObjectResponse response = client.GetObject(request);
using (Stream responseStream = response.ResponseStream)
{
    var bytes = ReadStream(responseStream);
    var download = new FileContentResult(bytes, "application/pdf");
    download.FileDownloadName = filename;
    return download;
}

public static byte[] ReadStream(Stream responseStream)
{
    byte[] buffer = new byte[16 * 1024];
    using (MemoryStream ms = new MemoryStream())
    {
        int read;
        while ((read = responseStream.Read(buffer, 0, buffer.Length)) > 0)
        {
            ms.Write(buffer, 0, read);
        }
        return ms.ToArray();
    }
}

Answer 2

另一种选择:

Stream rs;    
using (IAmazonS3 client = Amazon.AWSClientFactory.CreateAmazonS3Client())
{
    GetObjectRequest getObjectRequest = new GetObjectRequest();
    getObjectRequest.BucketName = "mybucketname";
    getObjectRequest.Key = "mykey";

    using (var getObjectResponse = client.GetObject(getObjectRequest))
    {
              getObjectResponse.ResponseStream.CopyTo(rs);
    }
}    

Answer 3

Stream现在有异步方法。在 C# 8 中，您可以这样做：

public async Task<byte[]> GetAttachmentAsync(string objectPointer)
{
    var objReq = new GetObjectRequest
    {
        BucketName = "bucket-name",
        Key = objectPointer,    // the file name
    };

    using var objResp = await _s3Client.GetObjectAsync(objReq);
    using var ms = new MemoryStream();
    await objResp.ResponseStream.CopyToAsync(ms, _ct);  // _ct is a CancellationToken
    return ms.ToArray();
}

这不会在 IO 发生时阻塞任何线程。