Question: Post JSON data without file

For context:

I have an app that is often used in low/no service areas, and needs to upload small JSON objects. I currently queue requests while offline, and then when online again I send them using Dio.
However I want these requests to happen in the background so I can still post the data if the user doesn't have the app open when they regain service.

Does flutter_uploader support uploading just JSON data without uploading a file? And are uploads by default queued until the phone regains connectivity?