http://wenku.baidu.com/link?url=sZiWt1t7-KvqM33lxSZOUbPKXx5RRWmUDmGxghb8LBXglr0pdMEam9H-0vnFPtBkE9COZI0lZ4JJGF1ip7IzytOkweSkVOBkBSQ0vpK4jt7
http://www.cnblogs.com/chef/archive/2012/07/18/2597279.html