说明：  不用自己写SQL去数据库存取对象。 你的代码仅仅和对象关联，自动产生SQL语句，并确保对象提交到正确的表和字段中去. 只要设计好数据库自动生成工厂模式的3层结构代码。
(Do not have to write SQL access to database objects. Your code and objects is only related to automatically generate SQL statements and to ensure that the object submitted to the correct table and field to go. So long as the design of the database automatically generated factory pattern layer 3 of the code.)