Classes not unloaded after undeployment

I deployed a small web application with one single JSF and one managed bean, accessed the page and then undeployed the application. I found the classes of this application had never been unloaded via monitoring with Java VistualVM, also using '-XX:+TraceClassUnloading' JVM option proved the classes not unloaded.
Then checking the heap dump of it, I found there were instance for each enum item (the managed bean has one enum type field, which is always initialized when the managed bean constructed) and one array instance including these enum instances.
Please refer to the attachment for the same application. I started to verify the classloader memory leak issue because we found hot redeployment of our real application swallow some memory each time, then after lots of redeployment the server was short of memories.