Extjs中上传文件后返回的json内容是文件下载

在使用Extjs这里的javascript框架开发文件上传的功能的时候，经常会遇到这个问题，参考了http://www.oschina.net/question/107380_151555里面的内容，得也解决，原来根本原因是：ajaxfileupload不支持响应头ContentType为application/json设置。

@RequestMapping(value = "uploadmodulefile.do")public ActionResult uploadModuleFile(UploadFileBean uploadExcelBean, BindingResult bindingResult,HttpServletRequest request, HttpServletResponse response) throws IOException {ActionResult result = moduleService.uploadModuleFile(uploadExcelBean, bindingResult, request);JSONObject jsonObject = new JSONObject();jsonObject.put("success",result.getSuccess());jsonObject.put("msg", result.getMsg());jsonObject.put("tag", result.getTag());response.getWriter().write(jsonObject.toString());return null;}