Rails? Been there. Grails? Done that. Both are decent. Rails is very good, but the abuse of open classes gets old quickly. Grails is ok, but it's really just a thin veneer over a complex mix of Java projects, and God help you if you run into any problems, because you'll be dealing with a stack trace that's 1000s of lines long, and you be troubleshooting these underlying complex java libs. For me, the play framework (http://www.playframework.org) is the best Rails-like approach on a Java platform. It stays very close to rails, so if you know rails learning it is easy. It's very pragmatic and very fast. It doesn't require a compile step to see your changes. It just works. Best of all, the code is clean and easy to troubleshoot. I suggest you check it out.