How about use annotation to indicate template engine instead of file extention?

[djunhao]

file extention just uses .html/.htm, and java class uses annotation like this:

@Show(template="SomePage.html", engine="mvel")
public class SomePage {}

[dhanji]

Hmm, not a bad idea. Might take some doing to plumb it right through though. Do you want to submit a PR?