I realized that you do NOT
have log4j in your pom, you need these 3 dependencies to log with log4j and slf4j:
slf4j-api-x.x.x.jar
slf4j-log4j12-x.x.x.jar
log4j-x.x.x.jar
log4j and slf4j-log4j12 should have the same version.
Please also note the commet from @Stefan Lindenberg