Due to classpath visibility issues, you are encouraged to have all the required jars (including
struts jar et al.... plus commons-logging.jar etc..) at the same visibility level.
That is you have struts.jar and tiles jars in WEB-INF/lib and commons logging in weblogic classpath it will work. However if you have it the other way round - (Struts in weblogic classpath and commons logging in WEBINF/lib) it is guaranteed NOT to work since parent classloader (for the classpath) cannot see the classes loaded by child class loader
HTH.
Srikanth Shenoy
Author: Struts Survival Guide - Basics to Best Practices