String realName = "设置的文件名";
response.setContentType("application/octet-stream; charset=UTF-8");
if (StrUtil.isNotBlank(realName)) {
    // 设置文件名
    String disposition = "attachment; filename=" + URLEncoder.encode(realName, "UTF-8");
    // 设置下载文件名称
    response.setHeader("Content-Disposition", disposition);
}