Log4J does not log anything

See this answer: How to initialize log4j properly?

-Dlog4j.debug is very useful for problems like this

The most recent thing I changed that finally got logging working properly was changing the classloader mode to "PARENT_FIRST" and WAR classloader policy to "Application". The initial default configuration was "PARENT_FIRST"/"Module". I changed it to "PARENT_LAST"/"Application" on the advice of a co-worker who says logging works fine for them and this is the only change they have to make when they create a new sandbox for this application. I'm not sure why I had to go with "PARENT_FIRST"/"Application", but at least it works now.

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UPDATE:

I tried setting up a new workspace and I had the same problem. It turns out you need "PARENT_FIRST"/"Application" AND a file named org.apache.commons.logging.LogFactory in the META-INF/services with one line containing: "org.apache.commons.logging.impl.Log4jFactory". Not having the file causes logging to fail (typically with a message saying that a Log4J cannot be found).