public class CallbackHandlerImpl
extends java.lang.Object
implements javax.security.auth.callback.CallbackHandler

This is a clone of Tomcat default callback handler but with a better handling of the Generic Principals when more than one callback is used. For instance https://github.com/apache/tomcat/blob/master/java/org/apache/catalina/authenticator/jaspic/CallbackHandlerImpl.java#L96 keeps adding new Generic Principals even for the same name whereas the authenticator base https://github.com/apache/tomcat/blob/master/java/org/apache/catalina/authenticator/AuthenticatorBase.java#L956 randomly picks the first one. So it results in random failures