code: protected DaoResult createOrUpdate(Connection conn, T bo) {
          if (bo == null) {
              return null;
          }
          DaoResult result = create(conn, bo);
          DaoOperationStatus status = result.getStatus();
          if (status == DaoOperationStatus.DUPLICATED_VALUE
                  || status == DaoOperationStatus.DUPLICATED_UNIQUE) {
              result = update(conn, bo);
          }
          return result;
      }
docs: Create a new BO or update an existing one.
  
  @param conn
  @param bo
  @return
  @since 0.8.1