Advice on csv processing: bundled war or simple applet?

Hi all, Im looking for a bit of advice on how to proceed here.
I have just taken up the reins on a project which has a whole pile of code written, but not a single piece of documentation or single comment produced

It uses Spring, and JSP, both of which are new to me, bundles everything up into a War file, and then I need to deploy it as a portlet through a cms.
The main functionality I need to edit is for users to upload an xl file, then the application extracts the data and puts it into a database.
I need to do things like add more columns to the files, change the Db structure etc.
The biggest problem as I see it is figuring out what all the existing code actually does. The way the environment is setup to bundle as a war and deploy as a portlet, I dont have the opportunity to riddle it with system.out.printlns to figure the code out and make the required changes.
Would it be a viable option to start with something simpler, e.g the java.csv library. And just build a simple java application to extract the info from csv files, connect to the db and insert. Then I could convert this say to an applet and deploy it within the csv. This would provide all the functionality I would need for now.

Any thoughts or opinions greatly appreciated.
Thanks,
Eoin.

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