PermGen is consumed by Sun14ReflectionProvider more than necessary

Sun14ReflectionProvider has a constructor cache.
However, these caches are gone for every minor GC, because WeakReference of constructor hasn't been referred by anyone when the constructor finish instantiating the object. So, whenever getMungedConstructor is called, constructor is newly created.

The objects in PermGen space isn't collected when minor GC, so it causes frequent full GC.