code: public static String exampleOrderBy(Class<?> entityClass) {
          StringBuilder sql = new StringBuilder();
          sql.append("<if test=\"orderByClause != null\">");
          sql.append("order by ${orderByClause}");
          sql.append("</if>");
          String orderByClause = EntityHelper.getOrderByClause(entityClass);
          if (orderByClause.length() > 0) {
              sql.append("<if test=\"orderByClause == null\">");
              sql.append("ORDER BY " + orderByClause);
              sql.append("</if>");
          }
          return sql.toString();
      }
docs: example查询中的orderBy条件，会判断默认orderBy
  
  @return