OVal is an extensible object validation framework for Java 5 or later. Annotations (@NotNull) or XML configuration files can be used to express class constraints. OVal can optionally use AspectJ to enforce automatic validation (DbC)
How to use: https://sebthom.github.io/oval/USERGUIDE.html
OVal releases are available via the the Bintray JCenter Maven repository https://bintray.com/bintray/jcenter?filterByPkgName=oval