Vidya Ramachandren wrote:
What is the best approach to migrate an application from a technology (like Java) to Ruby on Rails?
Ask whoever needs the new application what the most important _new_ feature is that they need.
Build a view with one button that does that feature. Leave the old program online, deploy the new program, and tell your users to open that view to hit that button when they need it.
Ask your client what the next feature is that they need. When you add it, replicate a little of the old system into the new one. The point is to phase out the old system. That pattern is called "strangler fig". Eventually the most common usage of the system will not use the old parts, only the new parts.
The alternative is this:
Tip: Do not wait 2 years before deploying your app! Deploy it immediately and then add features to it.
Write unit tests for everything you do (and port the original tests over - if any!).