Jason Hunter explains in an article called The Innovator’s Dilemma: It’s Happening to Java why there’s such a big interest in Ruby on Rails from the big Java thinkers like himself:

Ruby on Rails today looks poised to eat Java’s mindshare on the web tier. If not Rails, then something else. Empirically 10 years seems like the right point. Java’s viewed as solid and stable, mature enough for the most stodgy business folks. That leaves a large soft underbelly for a technology intended to help small teams (10 or fewer) who just want to make a site that’s good enough without paying a high price in mental effort.

I’ve written earlier on Rails as a disruptive technology according to Christensen’s framework of thinking.