NullInputModule returns a null object. Use this if you want to
explicitly forbid a parameter to be filled. E.g. a database column
shall be filled with a default value, your forms never contain that
parameter but you don't want anyone to provide this parameter
manually.
author: Christian Haul version: $Id: NullInputModule.java 433543 2006-08-22 06:22:54Z crossley $