I just wasted about 4 hours trying to get validation workingbecause the docs say that validation.xml needs to be on "the classpath", whereas actually /META-INF/validation.xml needs to be on the classpath.

That is not the sort of thing one can just guess.

Not sure if docs or code is wrong, but /META-INF/validation.xml loads and if the file is at the root of the classpath it is not even read.