spring mvc 请求返回json数据

/**
* 提交数据
* @param account
* @param pwd
* @return
*/
@RequestMapping(value = "/upload")
@ResponseBody    //关键注解

public UploadFileInfo upload(@RequestParam MultipartFile file, HttpServletRequest request) { 

// 可以返回一个对象，自动封装json数据

UploadFileInfo fileinfo=null;
try {
fileinfo = UploadHelper.createUploadFileInfo(file);
} catch (Exception e) {
e.printStackTrace();
}
return fileinfo;
    }