mvc模式
http://wenku.baidu.com/link?url=kcuML7Kjts3QT0MdjA3tLtdNo-DCKjmIR_rYbb8dqhuuyHoN7txuMJ4eCz4qWTC3tUaz8W480b25B6HOwqbMlaxoC35kP4KWj06WBPHKkBu