How avoid or fixed the PermGen exception

This is what helps me get through this issue, specially when in development mode and you're deploying your app every now and then.

 Add or modify the ff jvm properties (I've set this in Glassfish web admin UI):

-XX:PermSize=256m
-XX:MaxPermSize=512m
-XX:+CMSPermGenSweepingEnabled
-XX:+CMSClassUnloadingEnabled