@Override
 public void update(String old_category_name, String new_category_name) throws ServiceException {
   logger.info("CategoryService.update");
   try {
     categoryDAO.update(old_category_name, new_category_name);
   } catch (PersistenceException ex) {
     logger.error("CategoryService.update failed!");
     throw (new ServiceException("Category update failed!"));
   }
 }
 @Override
 public void create(String category_name) throws ServiceException {
   logger.info("CategoryService.create");
   Category new_category = new Category();
   new_category.setName(category_name);
   try {
     categoryDAO.create(new_category);
   } catch (PersistenceException ex) {
     logger.error("CategoryService.create failed!");
     throw (new ServiceException("Category update failed!"));
   }
 }
 @Override
 public List<String> list() {
   logger.info("CategoryService.list");
   return categoryDAO.list();
 }