I had faced an issue with resource bundle variable resolver library after upgrading adf from 11.1.1.6 to 11.1.2.3.

Error:

Caused by: java.lang.ClassNotFoundException: javax.faces.el.VariableResolver
at weblogic.utils.classloaders.GenericClassLoader.findLocalClass(GenericClassLoader.java:297)
at weblogic.utils.classloaders.GenericClassLoader.findClass(GenericClassLoader.java:270)
at java.lang.ClassLoader.loadClass(ClassLoader.java:305)
at java.lang.ClassLoader.loadClass(ClassLoader.java:246)
at weblogic.utils.classloaders.GenericClassLoader.loadClass(GenericClassLoader.java:179)
at java.lang.ClassLoader.defineClass1(Native Method)