affirm
is a set of Java interfaces and XML-based
reference implementation designed to make server-side input validation
straightforward. While input validation is most relevant to web-based
applications, it is useful under many circumstances. The fundamental
scenario is that you have a collection of data that needs to be
systematically checked to ensure that is meets some predetermined
criteria. The act of validating the input results either in a
validated datum or some indication of failure and the optional
association to some feedback error message.