code: public final void register() {
          synchronized (this) {
              if (filterFactoryServiceRegistration != null) {
                  throw new IllegalStateException(String.format("%s [%s] has been registered.", getClass()
                      .getSimpleName(), this));
              }
              filterFactoryServiceRegistration = bundleContext.registerService(SERVICE_CLASSES, this, properties);
              LOGGER.info("Registered filterFactory for application {} with priority {}", getApplicationName(),
                  getPriority());
          }
      }
docs: <p>register.</p>