@Override

    protected void doGet(HttpServletRequest req, HttpServletResponse resp)

            throws ServletException, IOException {

        req.setCharacterEncoding("utf-8");

        resp.setContentType("text/html;charset=utf-8");

        PrintWriter out = resp.getWriter();

        Cookie cookie=new Cookie("my", "my name is lsh");

        cookie.setDomain(".demo.com");  //设置 demo.com所有的子域名都有效

        cookie.setPath("/");            //设置路径

        cookie.setMaxAge(60*60*24);     //设置有效时间  以秒为单位

        resp.addCookie(cookie);            //设置到请求头当中

        out.println("设置cookie成功");

    }