code: public void updateConstantMetaClass(MetaClassRegistryChangeEvent cmcu) {
          Class<?> classToUpdate = cmcu.getClassToUpdate();
          MetaClass newMetaClass = cmcu.getNewMetaClass();
  
          System.out.println("Class ["+classToUpdate+"] updated MetaClass to ["+newMetaClass+"]");
          Thread.dumpStack();
      }
docs: Called when the a constant MetaClass is updated. If the new MetaClass is null, then the MetaClass
  is removed. Be careful, while this method is executed other updates may happen. If you want this
  method thread safe, you have to take care of that by yourself.
  
  @param cmcu - the change event