OK, here's the deal:
The problem lays in class loading.
When I import org.apache.log4j.spi.LoggingEvent in my standalone JMS publisher, it is taken from log4j-1.2.8.jar on classpath.
But! when I import org.apache.log4j.spi.LoggingEvent in MBean (which is JMS subscriber) running on JBoss it is loaded from JBOSS_HOME/lib/log4j-boot.jar even thou I included log4j-1.2.8.jar in my MBean.jar, and added it to Class-Path: in MANIFEST.MF.
How to make JBoss to load LoggingEvent from jar included in Class-Path: of my jar instead of loading it from JBOSS_HOME/lib/log4j-boot.jar???
Thanks for answer in advance
As for now, renaming log4j-1.2.8.jar to log4j-boot.jar and putting it into JBOSS_HOME/lib/ helped. But I'm not yet sure if not harmed too...
Still hoping for new ideas