I've configured Mendix app to store files on Amazon S3 cloud by putting configuration "setting com.mendix.core.StorageService" = "com.mendix.storage.s3"
Everything works fine, but the problem is that files are stored in amazon bucket's root folder with names like "123e4567-e89b-12d3-a456-426655440000". It's because when file is saving to the cloud System.FileDocument internal attribute "__UUID__" is used as ObjectKey (filepath) of amazon file.
Question: is it possible to use custom string as ObjectKey of files when using com.mendix.storage.s3 as StorageService?
P.S. I've tried Amazon S3 Connector from app store, it works fine and custom ObjectKeys can be used, like "folder1/folder2/somefile.txt". But right now using previously mentioned implementation by setting StorageService is the only option.
No, this is not possible. You should expect that your Mendix app is managing the content in that S3 bucket for you, just like it manages its database for you. I'm curious why you want/need to look at those files directly on S3.