public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
response.setContentType("text/html;charset=UTF-8");
response.setCharacterEncoding("UTF-8");
response.setHeader("Content-disposition", "attachment;filename=aa.txt" );
byte[] aa="中国，你好".getBytes();
OutputStream out=response.getOutputStream();
out.write(aa);
out.close();
}