You’d be surprised how hard it is to find good information about how you’re supposed to setup validators that you can parameterize with attributes in your tags; most about validators is very basic and very JSF-only. Or you won’t be surprised at all, because you searched until loss of sanity like me and found this blog. Whatever, here you can read what I found out.

So at first I made the error in not realizing validators under Facelets should be defined in their own facelets tag library. I hadn’t really worked myself into the the theory behind Facelets; I just picked it up as I went… as I do with most things, but there you have it. Turns out Facelets actually makes things very easy concerning validators, were it not for one sneaky little detail:

parameterizable validators are stateful validators

We’ll come back to it, but validators generally lose state after the page has been built by Facelets and you have to manually restore that state (including the previously set parameters), by implementing the StateHolder interface.

Oracle has a good article on StateHolder Validators, though I only found it after I learned what to look for.

I resorted to a rather crude catch’em all solution, that tucks away the boilerplate code involved.

read on