We are currently in the process of refactoring our plugin API**(JDK 1.4 compliant)** which is shipped to our clients in the form of a jar file(ie, no need to have javascripts to be generated and so forth). This is a very lightweight plugin so that we have kept away as many dependent jars as possible like Spring. During this process we started to understand the need to have a proper validation methodology which is faciliated by some validation Framework. Strangly, I couldnt find much options in these lines (like other open source projects)apart from a few such as Commons Validator,Drools and Spring support.
Drools seems to be so complex for my needs. However Commons validator looks prehistoric in its style of validation.
I cannot use annotation based validation cause it has to be JDK 1.4 and would prefer something that could be externalized thereby not requiring to compile classes again in case of changes.
Are there better options available?