code:     protected Object readResolve()
          throws ObjectStreamException {
          AbstractBrokerFactory factory = getPooledFactoryForKey(_poolKey);
          if (factory != null)
              return factory;
  
          // reset these transient fields to empty values
          _transactional = new ConcurrentHashMap();
          _brokers = newBrokerSet();
  
          makeReadOnly();
          return this;
      }
  
  