code: @Transactional(readOnly = true)
      public E findByRoleName(String roleName) {
  
          SimpleExpression eqRoleName =
              Restrictions.eq("name", roleName);
  
          E role = dao.findByUniqueCriteria(eqRoleName);
  
          return role;
      }
docs: Returns the role for the given (unique) role name.
  If no role was found, null will be returned.
  
  @param roleName A unique role name.
  @return The unique role for the role name or null.