public ActionForward save(ActionMapping mapping, ActionForm actionForm, HttpServletRequest request, HttpServletResponse response) throws Exception
   {
      if (!isCancelled(request))
      {
         ActionErrors errors = new ActionErrors();
         SubscriptionDataForm form = (SubscriptionDataForm) actionForm;

         // Facade uses a stateless session bean behind the scenes.
         // Each call to the facade means one transaction.
         // The Hibernate session lives as long as the facade.
         ServerAdminFacade facade = new ServerAdminFacade();

         Subscription subscription = facade.findSubscriptionByNumber(form.getNumber());
   
         if (subscription == null)
         {
            subscription = new Subscription();
         }

         // Inspired by Cocoon Woody: a Binding is a class for copying data to and from a form from a model object.   
         SubscriptionDataFormBinding binding = new SubscriptionDataFormBinding();
         // Load reference data
         binding.loadLicenseTypes(facade, form);
         // Copy form values into the model object
         binding.saveFormToModel(form, subscription);
         try
         {
            // Passing the subscription back through the return value has to do with an EJB thing: changes
            // to parameters are lost.
            // This is a call that may lead to a StaleObjectStateException!
            subscription = facade.saveSubscription(subscription);
            facade.flush();

            // Second step: add some more data.
            Set duplicates = facade.checkIButtons(subscription, form.getIButtons());
            Set syntaxErrors = facade.validateIButtons(subscription, form.getIButtons());
            Set lengthErrors = facade.validateIButtonLengths(subscription, form.getIButtons());
            
            binding.setIButtons(subscription, form.filterIButtons(duplicates, syntaxErrors));
            binding.setIButtons(subscription, form.filterIButtons(null, lengthErrors));
            
            // This is another call that may lead to a StaleObjectStateException!
            subscription = facade.saveSubscription(subscription);
         }
         catch (ApplicationException ex)
         {
            if (ex.getCause() instanceof StaleObjectStateException)
            {
               // Tell user to try again
               errors.add(ActionErrors.GLOBAL_ERROR, new ActionError("errors.concurrency"));
               saveErrors(request, errors);
               
               // THIS IS IMPORTANT: in case of an error, your "old" session will not be used anymore,
               // and you'll get a net.sf.hibernate.HibernateException: Illegal attempt to associate a collection with two open sessions
               // because the "old" object will somehow be associated with the "old" and the "new" session...
               subscription = facade.findSubscriptionByNumber(form.getNumber());
            }
            else
            {
               throw ex;
            }
         }
         
         // Would lead to net.sf.hibernate.HibernateException: Illegal attempt to associate a collection with two open sessions
         // with a StaleObjectStateException (or any Hibernate exception for that matter) and NO call to reload a new subscription object.
         binding.loadFormFromModel(form, subscription);
         binding.loadLicenseTypes(facade, form);
   
         return mapping.findForward(ServerAdminConstants.FORWARD_SUCCESS);
      }
      else
      {
         return mapping.findForward(ServerAdminConstants.FORWARD_START);
      }
   }