code: @Override
      public T findOne(final I id) {
          return inTransaction(new Callable<T>() {
              @Override
              public T call() throws Exception {
                  return entityManager.find(entity, id);
              }
          });
      }
docs: Retrieves an entity by its id.
  
  @param id the id, must not be null
  @return the entity instance, {@literal null} if there are no entities matching the given id.