When building a jar file with maven, it will create a manifest file in META-INF/MANIFEST.MF. Its contents currently are:
Manifest-Version: 1.0
Set user.name variable to empty string.
user.name
mvn -Duser.name="" package
Or if you are using Eclipse add -Duser.name="" to VM arguments of Maven run configuration (Run -> Run As -> Maven build... -> JRE tab -> enter -Duser.name="" in VM arguments field).
-Duser.name=""