有实例，讲解怎样更好的持久化，如何把数据库丢一边。优先设计业务层，将数据库层放在后边设计，并不是十分难的，恰恰相反，这种方式对于业务的理解，更加有好处。-How better to explain persistence, how to throw aside the database. To give priority to the business layer, database layer on the back design, is not very difficult, on the