Java 使用IE浏览器下载文件，文件名乱码问题

if (req.getHeader("user-agent").toLowerCase().contains("msie")) {  
        // IE  
    filename = URLEncoder.encode(filename, "UTF-8");  
} else {  
        // 非IE  
    filename = new String(filename.getBytes("UTF-8"), "iso-8859-1");  
}  

try {
                String fileName = attachmentFile.originalName();
                String userAgent = request.getHeader("user-agent").toLowerCase();  
                if (userAgent.contains("msie") || userAgent.contains("like gecko") ) {  
                        // win10 ie edge 浏览器 和其他系统的ie  
                    fileName = URLEncoder.encode(fileName, "UTF-8");  
                } else {  
                        // fe  
                    fileName = new String(fileName.getBytes("utf-8"), "iso-8859-1");  
                }  
                response.setCharacterEncoding("utf-8");
                response.setContentType("multipart/form-data");
                response.setHeader("Content-Disposition",
                        "attachment;fileName=" + fileName);
                String path = attachmentFile.path();
                InputStream inputStream = new FileInputStream(new File(path));

                OutputStream os = response.getOutputStream();
                byte[] b = new byte[2048];
                int length;
                while ((length = inputStream.read(b)) > 0) {
                    os.write(b, 0, length);
                }

                // 这里主要关闭。
                os.close();

                inputStream.close();
            } catch (FileNotFoundException e) {
                e.printStackTrace();
            } catch (IOException e) {
                e.printStackTrace();
            }