code: public void doAfterDeserialization() {
          if ( listeners == null ) {
              listeners = new ArrayList<SessionListener>();
          }
          if ( notes == null ) {
              notes = new ConcurrentHashMap<String, Object>();
          }
      }
docs: Performs some initialization of this session that is required after
  deserialization. This must be invoked by custom serialization strategies
  that do not rely on the {@link StandardSession} serialization.