从S3下载所有文件并将它们上传到同一文件夹中

Question

I have enabled versioning on the bucket whenever a new bucket is created. But for backward compatibility (buckets which are already created), i'm downloading all files/keys and uploading again. I'm doing this:

fullObject = s3Client.getObject(new GetObjectRequest(bucketName, key));

But i am not able to figure out while uploading how to upload file in their specific folder. Or is there another solution to fix backward compatibility.

Answer 1

S3 doesn't really have folders, it "fakes" it with logic that looks for common prefixes separated by "/". The "key" is the full path name of the file within the bucket.

It sounds like you are doing a get and then want to do a put of the same bytes to the same key in the bucket. If that is what you want to do, then just use the same key that you used for getting the object.

In a bucket that has versioning turned on, this will result in two copies of the file. It is not clear why you would want to do that (assuming that you are writing back exactly what you are reading). Wouldn't you just end up paying for two copies of the same file?

My understanding is that if you turn on versioning for a bucket that already has files in it, that everything works the way you would expect. If a pre-existing file gets deleted, it just adds a delete marker. If a pre-existing file gets overwritten, it keeps the prior version (as a prior version of the new file). There is no need to pro-actively rewrite existing files when you turn on versioning. If you are concerned, you can easily test this through either the S3 Console, the command line interface, or through one of the language-specific APIs.