/**
    * Closes the session factory, releasing all held resources.
    *
    * <ol>
    * <li>cleans up used cache regions and "stops" the cache provider.
    * <li>close the JDBC connection
    * <li>remove the JNDI binding
    * </ol>
    *
    * Note: Be aware that the sessionfactory instance still can
    * be a "heavy" object memory wise after close() has been called.  Thus
    * it is important to not keep referencing the instance to let the garbage
    * collector release the memory.
    */
   public void close() throws HibernateException {

      if ( isClosed ) {
         log.trace( "already closed" );
         return;
      }

      log.info("closing");

      isClosed = true;

      Iterator iter = entityPersisters.values().iterator();
      while ( iter.hasNext() ) {
         EntityPersister p = (EntityPersister) iter.next();
         if ( p.hasCache() ) {
            p.getCacheAccessStrategy().getRegion().destroy();
         }
      }

      iter = collectionPersisters.values().iterator();
      while ( iter.hasNext() ) {
         CollectionPersister p = (CollectionPersister) iter.next();
         if ( p.hasCache() ) {
            p.getCacheAccessStrategy().getRegion().destroy();
         }
      }

      if ( settings.isQueryCacheEnabled() )  {
         queryCache.destroy();

         iter = queryCaches.values().iterator();
         while ( iter.hasNext() ) {
            QueryCache cache = (QueryCache) iter.next();
            cache.destroy();
         }
         updateTimestampsCache.destroy();
      }

      settings.getRegionFactory().stop();

      if ( settings.isAutoDropSchema() ) {
         schemaExport.drop( false, true );
      }

      try {
         settings.getConnectionProvider().close();
      }
      finally {
         SessionFactoryObjectFactory.removeInstance(uuid, name, properties);
      }

      observer.sessionFactoryClosed( this );
      eventListeners.destroyListeners();
   }