ajax判断远程文件是否存在 后台代码实现

@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;
}