JSR 303 is a specification of the Java API for Javabean validation in Java EE and Java SE. Apache BVal is designed to offer a class level constraint declaration and validation facility for Java developers. In addition, Apache BVal comes with a constraint metadata repository and query API. Apache BVal is TCK compliant, supports the fifth version of Java SE and is licensed under the Apache version 2.0 open-source license. Being developed using Java, Apache BVal is cross-platform and can be used on any operating system that comes with Java support (e.g. Mac OS X, Windows, Linux). Detailed instructions on how to install and use Apache BVal on your Mac are available HERE.