code: private <T> T doInterceptAfterQuery(Class<?> clazz, T t, StringBuilder sql, List<Object> args) {
          List<T> list = new ArrayList<T>();
          if (t != null) {
              list.add(t);
          }
          list = doInteceptAfterQueryList(clazz, list, 1, sql, args);
          return list == null || list.isEmpty() ? null : list.get(0);
      }
docs: t为null表示没有记录，因此等价于空list