文件的上传和下载

http://blog.youkuaiyun.com/zhy981167180/article/details/38425059

http://www.cnblogs.com/xdp-gacl/p/4200090.html

http://www.jb51.net/article/59408.htm

http://blog.youkuaiyun.com/xiazdong/article/details/7231977

http://www.cnblogs.com/xiaoluo501395377/archive/2012/10/26/2740882.html