Let's bear in mind that Java developers haven't all stood still -- mesmerized by the oncoming lights of RoR. A promising project aims to do similar scaffolds for CRUD applications in Java:

http://www.trailsframework.org/

The immediate response from RoR advocates will be that you still live in the strongly typed world of Java. I personally like my variables to know themselves. It is oddly Aristotelian for variable "foo" to know its identity as a String or Integer before I start throwing it around, but I'm old fashioned that way.

Ultimately Java isn't what is threatened by RoR, but rather Java developers. Rails has shown a better way to cut out the tedium of building database apps. There is no reason that any sensible developer can't learn from the model.