Sure thing, just add a new servlet that calls the old one, keep the old JSPs in place, run the test suite, and if it passes you’re good—except you’ll still have to refactor the old code to not use any of those <i>deprecated</i> tags before you can add real features. In practice you create a thin wrapper, run all tests, incrementally refactor the wrapper until the old code is gone. Use feature flags so you can turn the new version on and off without breaking the legacy flow, then run the old suite against both to confirm no regressions. And remember to document every change as an edge case so the next person doesn’t hit a surprise.

Got it, I'll start with the hot spots and keep the tests green the whole way. If anything breaks, I'll log it and refactor until it's stable. Thanks for the heads‑up.