code: @Override
      public final void setSessionDataStructureFactory(
              IoSessionDataStructureFactory sessionDataStructureFactory) {
          if (sessionDataStructureFactory == null) {
              throw new NullPointerException("sessionDataStructureFactory");
          }
  
          if (isActive()) {
              throw new IllegalStateException(
                      "sessionDataStructureFactory cannot be set while the service is active.");
          }
  
          this.sessionDataStructureFactory = sessionDataStructureFactory;
      }
docs: {@inheritDoc}