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！");  
    }  
}  

......  
    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;  
......