HttpServletResponse对象

获得输出流、文件下载：   http://www.cnblogs.com/xdp-gacl/p/3789624.html

                                 http://www.cnblogs.com/xiaoqv/archive/2012/05/14/2500725.html

                                http://www.cnblogs.com/xdp-gacl/p/3798347.html（详细）