Having added log4mongo to some of my older projects, I remove the old log4j-1.xxxx.jar and replace with log4j-1.2.15.jar. I start a junit test as usual and get an exception:
Go into the project properties in Eclipse (right-click on the project in the Package Explorer, hit properties), go to Order and Export tab and click on the log4j-1.2.15.jar. Press the Top button. Hit OK and re-run your test. Hey presto, sorted.
I haven’t done enough digging but I think it something to with the commons-logging having a out of date api and being first in the classpath it can findthe latest version of LoggingEvent.