转自：http://www.cnblogs.com/TomXu/p/3756794.html
http://www.cnblogs.com/Joans/archive/2012/02/08/2342887.html
http://www.cnblogs.com/younggun/archive/2010/09/26/1836300.html
http://www.360doc.com/content/14/0619/09/10504424_387971542.shtml
原文：http://www.cnblogs.com/chengjun/p/4330536.html