@RequestMapping("/isExcelExist")
    @ResponseBody
    public Object isExcelExist(HttpServletRequest request) {
        Map<String,Object> resMap = new HashMap<String,Object>();
        try {

            String url = request.getParameter("downPath");
            URL serverUrl = new URL(url);
            HttpURLConnection urlcon = (HttpURLConnection) serverUrl
                    .openConnection();
            // 文件存在‘HTTP/1.1 200 OK’ 文件不存在 ‘HTTP/1.1 404  Not Found’
            String message = urlcon.getHeaderField(0);
            if (StringUtils.isNotBlank(message)
                    && message.startsWith("HTTP/1.1 404")) {
                // 不存在
                resMap.put("success",false);
                resMap.put("msg","文件不存在！");
            } else {
                resMap.put("success",true);
                resMap.put("msg","文件存在！");
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
        return resMap;
    }