The Grails team has been up to some really cool stuff. I’ve played with the recently released Grails 4 and it is a nice evolution of the framework. The upgrade path from 3 to 4 also looks to be much much smoother than from 2 to 3.
It’s an promising trend industry wide to see more and more of the dynamism developers love move to the compiler level vs the runtime level. The accomplishment with this is both for the code that is produced, and dramatically shortening the feedback loop for bugs, or even eliminating whole classes of errors.