springmvc中使用response的out.print问题

public ModelAndView handleRequest(HttpServletRequest request,
        HttpServletResponse response) throws Exception {
    Member member = (Member) RequestUtil.parseRequestToObject(request,Member.class);
    if (member == null) {
        jzLogic.insertMember(member);
        return new ModelAndView("index");
    } else {
        return new ModelAndView("Error", "message", "账号已被注册！");
    }
}  

在上述代码中如果需要使用out.print打印如alert("");信息可按以下方式进行：

......
    response.setContentType("text/html; charset=gbk");
    PrintWriter out = response.getWriter();
    out.println("<script language='javascript'>");
    out.println("alert('账号已被注册！');");
    out.println("history.back();");
    out.print("</script>");
    return null;
......  

return null，如果return new ModelAndView则直接转发