Java/JSP : Making a executable Java working as webapp

I have a standard java project working local made by another person i know. It's about data retrieving. I need to develop a web app supposed to do the same thing but accessible by anyone via browser. I CAN'T edit the code for that purpose, at least some implementation details. A kind of black box.

Can you suggest me the best approach to make a webapp based on a local executable app through JSP & servlet ecc?