导出excel表单,extjs用ajax写没反应,请问用from提交怎么写

使用location.href，后台输出文件流

 HttpServletResponse.setContentType("text/html;charset=GBK");
        HttpServletResponse.setCharacterEncoding("GBK");
        OutputStream os = HttpServletResponse.getOutputStream();// 取得输出流
        HttpServletResponse.reset();// 清空输出流
        HttpServletResponse.setHeader("Content-disposition",
                "attachment; filename=" + new String(fileName.getBytes("GB2312"), "ISO8859-1") + ".xls");
        // 设定输出文件头
        HttpServletResponse.setContentType("application/msexcel");// 定义输出类型