Java Spring文件下载

Question

@RequestMapping(value = "download", method = RequestMethod.GET)
public String download(
        @RequestParam(value = "questionId") String question,
        HttpServletResponse response, HttpServletRequest request) {

    QuestionDto questionDto = null;

    try {
        Integer questionIdentifier = Integer.parseInt(question);
        questionDto = this.userHelpAndSupportService.getQuestionById(questionIdentifier);
        String filename1 = questionDto.getAttachmentName();

        if (filename1.contains(".doc") || filename1.contains(".docx")) {
            response.setContentType("application/vnd.ms-word");
            response.setHeader("Content-Disposition",
                    "attachment;filename=" + filename1);
        } else if (filename1.contains(".xls")
                || filename1.contains(".xlsx")) {
            response.setContentType("application/vnd.ms-excel");
            response.setHeader("Content-Disposition",
                    "attachment;filename=" + filename1);

        } else if (filename1.contains(".pdf")) {
            response.setContentType("application/pdf");
            response.setHeader("Content-Disposition",
                    "attachment;filename=" + filename1);
        } else if (filename1.contains(".txt")) {
            response.setContentType("application/txt");
            response.setHeader("Content-Disposition",
                    "attachment;filename=" + filename1);
        }
        OutputStream out = response.getOutputStream();
        FileCopyUtils.copy(questionDto.getAttachment(), out);
        out.flush();
        out.close();
    } catch (Exception e) {
        if (questionDto != AdPlannerAdminConstants.NULL){
            PlatformLoggerUtil.info(this.getClass(),"The filename to be downloaded is "+questionDto.getAttachmentName());
            PlatformLoggerUtil.error(this.getClass(),"Exception in AdminHelpAndSupportController:download "+e);
        }


    }
    return null;
}

每当我尝试下载文件时，在mozilla和chrome中，文件的扩展名都会针对某些文件进行更改。下载的文件不可读。如何解决这个问题？