in order to support custom  caller information.

For example
Intercept the execution of a handler
...
String className = pjp.getThis().getClass().getName();
    FQCNHelper.setFQCN(className);
// preHandle.
logBefore(log, traceLog, pjp.getSignature().toShortString(), pjp.getArgs());
FQCNHelper.clear();
...