Sick of writing validators? Sick of XML? Sick of framework specific validation? Sick of complex formats and extra stuff you never use? Well, I was too and now I've outsourced something that might help you too reducing these pains.
Check out YAV.
YAV is a simple, framework independent, lightweight Java validation tool. It applies validations directly to domain models through annotations. It checks for mandatoriness, email, range and regex. If you need, create your own methods to perform more complex validations. It is JSR-303 non-compliant - thank goodness :)
Currently integrates nicely with Spring2.5, Struts2 is on the way.
It also has ValidationTestCases that minimize annoyingly repetitive testing tasks.
As always, there are a few edges to trim, but it works.