One presumes you are using Java CAPS 5.1 rather than ICAN 5.0?
In 5.1.2 Integration Server does not use log4j.
You configure logging for collaborations, and other components, using the Integration Server Administration console, Logging Tab, Log levels subtab.
By default collaboration logging is not turned specifically on - root level logging is typically set at INFO so anything you log in a collaboration at DEBUG level will not show up in the log.
Add a category STC.eGate.CMap.Collabs and set the level to FINE
run your collab with at least one logger.debug() to see the complete package name.
Set STC.eGate.CMap.Collabs to INFO
Add STC.eGate.CMap.Collabs.<package_name> logging category and set logging level as required.