In the configuration I'm building, we have three instances of Tomcat in separate JVMs running on a single machine. We have given each of these different names (tomcat_vm01, tomcat_vm02, etc.). In order to minimize the amount of duplicated configuration across instances, I've built a single logging.properties file that works for all instances using variable substitution; I pass JVM variable settings in when I start Tomcat, and the VM_NAME variable will be substituted into the logging.properties file, creating a separate log file for each Tomcat instance.

This configuration works fine if my log prefix looks like this:
4admin.org.apache.juli.FileHandler.prefix = ${VM_NAME}.admin.

Ideally, however, the log's prefix would be:
4admin.org.apache.juli.FileHandler.prefix = admin.${VM_NAME}.

The first case works perfectly, and in the second case, the variable doesn't resolve. Does anyone have any idea what may be causing this issue?