I wish the Play framework was available when I did server side Java
Even though Rails is my "go to" platform for efficiently writing web apps, I like to keep up with Scala + Lift, Java options on AppEngine, Clojure + Compojure, Seaside, etc. I just revisited the Play framework and I must admit some real regret that something like Play was not available when I did a lot of server side Java work.
Play borrows a lot from opinionated frameworks like Rails and a quick study is enough to be productive largely because of the similarities to Rails in the ease of setting up routes, database access, nice MVC separation, etc. Probably the neatest feature of Play is that Java source code is compiled on the fly using the Eclipse Java compiler so if you edit a Java controller of model file and refresh a web page you instantly see the effects of the code change. There is a Scala sub-project of Play also.