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