@Controller

public class FileController {

    private Logger log = LoggerFactory.getLogger(FileController.class);

    @RequestMapping(value="/download/oldio}", method = RequestMethod.GET)

    public void download(HttpServletRequest request, HttpServletResponse response,String fileName) throws IOException{

         String folder = "C://Users/xxx/Downloads/0714";

         File file = new File(folder, fileName);

         if(file.exists()){

             response.setContentType("MimeType");

             response.addHeader("Content-Disposition","attachment;filename=" +fileName);

             response.setContentLength((int)file.length());

             //Java IO

             InputStream inputStream = new BufferedInputStream(new FileInputStream(file));

             //Copy bytes from source to destination(outputstream in this example), closes both streams.

             FileCopyUtils.copy(inputStream, response.getOutputStream());

             log.info("download success! ---" + fileName);

         }else {

             throw  new Error("file not exist");

         }

     }

    @RequestMapping(value="/download/nio}", method = RequestMethod.GET)

    public void downloadfornio(HttpServletRequest request, HttpServletResponse response, String fileName) throws IOException{

        String folder = "C://Users/xxx/Downloads/0714";

        File file = new File(folder, fileName);

        if(file.exists()){

            response.setContentType("MimeType");

            response.addHeader("Content-Disposition","attachment;filename=" +fileName);

            response.setContentLength((int)file.length());

            //128 * 1024 = 128K

            int bufferSize = 131072 * 6;

            FileInputStream fileInputStream = new FileInputStream(file);

            FileChannel fileChannel = fileInputStream.getChannel();

            // 6 * 128K = 768K = 786432

            ByteBuffer buffer = ByteBuffer.allocateDirect(786432);

            byte[] byteArr = new byte[bufferSize];

            int nRead, nGet;

            try {

                while ((nRead = fileChannel.read(buffer)) != -1){

                    if(nRead == 0){

                        continue;

                    }

                    buffer.position(0);

                    buffer.limit(nRead);

                    while (buffer.hasRemaining()){

                        nGet = Math.min(buffer.remaining(), bufferSize);

                        // read bytes from disk

                        buffer.get(byteArr,0,nGet);

                        //write bytes to output

                        response.getOutputStream().write(byteArr);

                    }

                    buffer.clear();

                }

                log.info("download success! ---" + fileName);

            }catch (IOException e){

                e.printStackTrace();

            }finally {

                buffer.clear();

                fileChannel.close();

                fileInputStream.close();

            }

        }else {

            throw  new Error("file not exist");

        }

    }

}

@RunWith(SpringRunner.class)

@SpringBootTest

public class FileControllerTest {

    private MockMvc mockMvc;

    @Autowired

    private WebApplicationContext wac;

    private  FileController fc;

    @Before

    public  void  setup(){

        mockMvc = MockMvcBuilders.webAppContextSetup(wac).build();

        fc = this.wac.getBean(FileController.class);

    }

    @Test

    public void compareTime() throws Exception {

        String fileName = "11.tar.gz";

        MockHttpServletRequest request = new MockHttpServletRequest();

        MockHttpServletResponse response = new MockHttpServletResponse();

        long c = System.currentTimeMillis();

        fc.downloadfornio(request, response, fileName);

        long d = System.currentTimeMillis();

        System.out.println("nio download takes :" + (d - c) );

        long a = System.currentTimeMillis();

        fc.download(request, response,fileName);

        long b = System.currentTimeMillis();

        System.out.println("io download takes :" + (b - a) );

    }

}

nio download takes :144

io download takes :164