Ant deploy scripts and team production cycles, make modifying of configuration files vs. java files with recompilation a moot point in my experience.

Since we are dealing with compiled annotations, just like caching reflected properties of beans (quite common), I could also see caching of validation data on a per type basis. The reflection only occurs once then, caching both the annotation state and the ValidateHandler. If you look at how much reflection already exists within frameworks, reflection for annotations (once) really isn't that big of a deal. I left it out of the sample code as to not confuse the meat of this implementation.

As stated in goal of this example framework, the end result is extremely easy for developers to grasp (just drop a @ValidateRequired). Developing new JSF validators w/ tag support is just as complex as adding a new annotation (not that either is overly difficult IMHO).