I want to use Apache validator in my project. But I don't know how to go further after creating an instance of Validator. I am performing validation in a filter. Is it a good way? And if it is, how to proceed further?
Commons validator source distribution comes with examples. Check version of the one you are using and download the source from apache website (look for files similar to commons-validator-1.4.0-src.zip). That should get you started with validator usage.
Regarding validation in filter (assuming servlet filters), the details are not enough. Whether its a good way or not depends on what you are trying to validate. A typical use of a filter is to log message arrivals but not to validate the request content. But that doesnt mean one should not. As i said it all depends on what you are trying to achieve.