code: public void flush() {
          if (active) {
              for (Iterator<Entry<String, Object>> it = attributes.entrySet().iterator(); it.hasNext();) {
                  final Entry<String, Object> entry = (Entry<String, Object>) it.next();
                  final String key = (String) entry.getKey();
                  try {
                      originalSession.setAttribute(key, new SerializedObjectHolder(key, entry.getValue()));
                  } catch (final IllegalStateException e) {
                      return;
                  } catch (final Exception e) {
                      logger.info("Failed to set session attribute as HotDeploy: " + key, e);
                  }
              }
          }
      }
docs: =====