NoClassDefFoundError LogManager

PROBLEM:
NoClassDefFoundError: Could not initialize class org.apache.log4j.LogManager

SOLUTION:
remove:  -Dlog4j.configuration=file:conf/log4j.xml


Docs:
slf4j: https://www.slf4j.org/legacy.html
jars:
commons-logging-1.2.jar
jcl-over-slf4j-1.7.7.jar or jul-to-slf4j-1.7.12.jar
log4j-1.2.18*.jar
slf4j-api-1.7.12.jar
slf4j-log4j12-1.7.12.jar