code: public static BeanQuery<Map<String, Object>> select(String selectString) {
      return new BeanQuery<Map<String, Object>>(new StringSelector(selectString));
    }
docs: Create a BeanQuery instance with select String, the select String is in
  format "propertyName[ as alias][,propertyName[ as alias]]". For example:<br>
  <code>BeanQuery beanQuery=select("name, price as p, address.officeAddress as address");</code>
  When executing the BeanQuery instance created in above code will
  return a list of map with 3 keys:[name,p,address].