Hi,
I could think of the below :
Have a service user to read the file, which will be probably be placed at a specific DAM location. Sharing few snippets, which might help you.
Node assetNode = session.getNode(damPath);
Use ResourceResolver, adapt it to an Asset and further do the below :
BufferedReader br = new BufferedReader(new InputStreamReader(asset.getRendition(Constants.ORIGINAL).getStream()));
For further processing, the below link might help
https://www.mkyong.com/java/how-to-read-and-parse-csv-file-in-java/