Spring AOP is
NOT preferred over log4j or common-logging?
Spring AOP is used in conjunction with and logging framework - log4j, slf4j or commons-logging to separate logging concern from your main business code.
I suggest looking at the spring source provided aspect training -
http://www.springsource.com/training/free-online-training-developing-aspects-a
It provides a great overview of AOP & the example used is of
logging so you'll get a really good understanding of how to use Spring AOP for logging.