如何从S3中获取GetObjectResponse的字节数

本文关键字：GetObjectResponse 字节数获取 S3 | 更新日期: 2023-09-27 18:25:59

我正在从AmazonS3检索一个文件。我想把文件转换成字节，这样我就可以下载如下：

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

我这里有文件：

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

我知道回应。WriteResponseStreamToFile（），但我想将该文件下载到常规下载文件夹中。如果我将GetObjectResponse转换为字节，我可以返回该文件。我该怎么做？

如何从S3中获取GetObjectResponse的字节数

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();
    }
}

只是另一个选项：

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);
    }
}

我很难让Alex提供的更干净的方法发挥作用（不确定我缺少了什么），但我想在没有Erica提供的额外ReadStream方法的情况下完成它（尽管它有效）。。。这就是我最终要做的事情：

var s3Client = new AmazonS3Client(AccessKeyId, SecretKey, Amazon.RegionEndpoint.USEast1);
    using (s3Client)
    {
        MemoryStream ms = new MemoryStream();
        GetObjectRequest getObjectRequest = new GetObjectRequest();
        getObjectRequest.BucketName = BucketName;
        getObjectRequest.Key = awsFileKey;
        using (var getObjectResponse = s3Client.GetObject(getObjectRequest))
        {
            getObjectResponse.ResponseStream.CopyTo(ms);
        }
        var download = new FileContentResult(ms.ToArray(), "image/png"); //"application/pdf"
        download.FileDownloadName = ToFilePath;
        return download;
    }

Stream现在有异步方法。在C#8中，你可以这样做：

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。