ReadableByteChannel readableByteChannel = Channels.newChannel(url.openStream());

FileOutputStream fileOutputStream = new FileOutputStream(FILE_NAME);
FileChannel fileChannel = fileOutputStream.getChannel();

fileOutputStream.getChannel().transferFrom(readableByteChannel, 0, Long.MAX_VALUE);

/**NIO文件下載工具類
 * @author olalu
 */
public class NioDownloadUtils {

    /**
     * @description:
     * @param file: 要下在文件
     * @return: void
     */
    public static void downloadDoc(File file,HttpServletResponse response) throws IOException {
        OutputStream outputStream = response.getOutputStream();
        String contentType = Files.probeContentType(Paths.get(file.getAbsolutePath()));
        //設置響應頭
        response.setHeader("Content-Type", contentType);
        response.setHeader("Content-Disposition", "attachment;filename="+ new String(file.getName().getBytes("utf-8"),"ISO8859-1"));
        response.setContentLength((int) file.length());
        //獲取文件輸入流
        FileInputStream fileInputStream = new FileInputStream(file);
        //獲取輸出流通道
        WritableByteChannel writableByteChannel = Channels.newChannel(outputStream);
        FileChannel fileChannel = fileInputStream.getChannel();
        //采用零拷貝的方式實現(xiàn)文件的下載
        fileChannel.transferTo(0,fileChannel.size(),writableByteChannel);
        //關閉對應的資源
        fileChannel.close();
        outputStream.flush();
        writableByteChannel.close();
    }

    public static void downloadDoc(String path,HttpServletResponse response) throws IOException {
        File file = new File(path);
        if (!file.exists()){
            throw new RuntimeException("文件不存在");
        }
        downloadDoc(file,response);
    }

}

/**
     * 文件上傳方法
     */
    public static Result uploading(MultipartFile file) {
        //獲取文件名
        String realName = file.getOriginalFilename();
        String newName = null;
        if(realName != null && realName != ""){
            //獲取文件后綴
            String suffixName = realName.substring(realName.lastIndexOf("."));
            //生成新名字
            newName = UUID.randomUUID().toString().replaceAll("-", "")+suffixName;
        }else {
            return Result.fail("文件名不可為空");
        }
        //創(chuàng)建流
        FileInputStream fis = null;
        FileOutputStream fos = null;
        //創(chuàng)建通道
        FileChannel inChannel = null;
        FileChannel outChannel = null;
        try {
            fis = (FileInputStream)file.getInputStream();
            //開始上傳
            fos = new FileOutputStream(UPLOAD_URL+"\\"+newName);
            //通道間傳輸
            inChannel = fis.getChannel();
            outChannel = fos.getChannel();
            //上傳
            inChannel.transferTo(0,inChannel.size(),outChannel);

        }catch (IOException e){
            return Result.fail("文件上傳路徑錯誤");
        }finally {
            //關閉資源
            try {
                if (fis != null) {
                    fis.close();
                }
                if (fos != null) {
                    fos.close();
                }
                if (inChannel != null) {
                    inChannel.close();
                }
                if (outChannel != null) {
                    outChannel.close();
                }
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        return Result.ok(newName);

    }