code: private static XmlElement generateCommColumnsSelective(List<IntrospectedColumn> columns, String prefix, boolean bracket, int type) {
          XmlElement trimEle = generateTrim(bracket);
          for (IntrospectedColumn introspectedColumn : columns) {
              generateSelectiveToTrimEleTo(trimEle, introspectedColumn, prefix, type);
          }
          return trimEle;
      }
docs: 通用遍历columns
  @param columns
  @param prefix
  @param bracket
  @param type    1:key,2:value,3:set
  @return