This is a set of libraries, originally hosted on Kenai.com, and used in NetBeans, for ad-hoc validation of objects, with a number of very useful built in validators (email addresses, IP addresses, URLs, that sort of thing), and with an emphasis on good, meaningful, human-readable error messages.
All error messages from the built in validators are localized into English, French, Italian and German.
Originally intended for Swing applications, the GUI classes have been factored out into a separate project.
The nbstubs project includes stub versions of localization-related classes from NetBeans and is needed
when used outside of NetBeans - the simplevalidation-standalone project includes that in its JAR file.
The original project documentation can be viewed here
As of May 6, 2019, the groupId has been changed to com.mastfrog in order to be able to deploy the
artifacts to Maven central.