I'm working on a code base that dates back at least 15 and possibly as much as 20 years, where the older code is still functional but includes thousands of JSPs full of Connection, PreparedStatement, and ResultSet objects, as well as hard-coded SQL, to manage data access.
Yes, it's about as painful as it sounds ... but my question specifically is that, since it still works, what are all the other drawbacks than simple functionality?
I want to write up a proposal to submit to the owner of the company so he'll pony up the cash to get this all updated to modern standards. I can think of many of the more obvious issues, but from a business perspective, what looming crises are on the horizon that can only be avoided by turning the ship now?
[Edit] To clarify, I'm not looking for advice or suggestions on what technologies to use. As a question of software development I'm looking for a short list of issues relevant in 2016 that make good business sense, to use as part of the proposal. For example, what are the "hidden costs" to this architecture, what are the vulnerabilities and potential damage from failure, etc.