How to build SFTP server and image server on Linux cloud server

<dependency>
    <groupId>com.jcraft</groupId>
    <artifactId>jsch</artifactId>
    <version>0.1.49</version>
</dependency>

public class SFTPInfo {
    public static final String SFTP_REQ_HOST = "000.00.00.00"; //Cloud server ip
    public static final String SFTP_REQ_USERNAME = "00t"; // Username public static final String SFTP_REQ_PASSWORD = "00"; // Password public static final int SFTP_DEFAULT_PORT = 22; // Port public static String basePath="/usr/games/images"; // The main directory where the file is saved on the server (this is the file upload path)
    public static String baseUrl="https://##.##.com/images"; //Online domain name access specifies the nginx access path (the path is critical here)
}

import java.io.InputStream;
import java.util.Properties;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import com.jcraft.jsch.Channel;
import com.jcraft.jsch.ChannelSftp;
import com.jcraft.jsch.JSch;
import com.jcraft.jsch.JSchException;
import com.jcraft.jsch.Session;
import com.jcraft.jsch.SftpException; 
public class SftpUtils {
    private static final Logger LOG = LoggerFactory.getLogger(SftpUtils.class);
 
    /**
     * Reference Example *
     * @param args
     */
    public Channel getChannel(Session session) {
        Channel channel = null;
        try {
            channel = session.openChannel("sftp");
            channel.connect();
            LOG.info("get Channel success!");
        } catch (JSchException e) {
            LOG.info("get Channel fail!", e);
        }
        return channel;
    }
 
    public Session getSession(String host, int port, String username,
                              final String password) {
        Session session = null;
        try {
            JSch jsch = new JSch();
            jsch.getSession(username, host, port);
            session = jsch.getSession(username, host, port);
            session.setPassword(password);
            Properties sshConfig = new Properties();
            sshConfig.put("StrictHostKeyChecking", "no");
            session.setConfig(sshConfig);
            session.connect();
            LOG.info("Session connected!");
        } catch (JSchException e) {
            LOG.info("get Channel failed!", e);
        }
        return session;
    }
 
    /**
     * Create Folder *
     * @param sftp
     * @param dir
     * Folder Name */
    public void mkdir(ChannelSftp sftp, String dir) {
        try {
            sftp.mkdir(dir);
            System.out.println("Folder created successfully!");
        } catch (SftpException e) {
            System.out.println("Failed to create folder!");
            e.printStackTrace();
        }
    }
 
    /**
     * @param sftp
     * @param dir
     * Upload directory * @param file
     * Upload file * @return
     */
    public Boolean uploadFile(ChannelSftp sftp, String dir, InputStream file,String fileName) {
        Boolean flag = false;
        try {
            sftp.cd(dir);
            if (file != null) {
                sftp.put(file, fileName);
                flag=true;
                return flag;
            } else {
                flag=false;
                return flag;
            }
        } catch (Exception e) {
 
            flag=false;
            return flag;
        }
    }
 
    /**
     * Download File *
     * @param directory
     * Download directory * @param downloadFile
     * Downloaded file * @param saveFile
     * The local path * @param sftp
     */
    public String download(String directory, String downloadFile,
                           String saveFile, ChannelSftp sftp) {
        String result = "";
        try {
            sftp.cd(directory);
            sftp.get(downloadFile, saveFile);
            result = "Download successful!";
        } catch (Exception e) {
            result = "Download failed!";
            LOG.info("Download failed!", e);
            ;
        }
        return result;
    }
 
    /**
     * Delete Files*
     * @param directory
     * To delete the directory where the file is located* @param deleteFile
     * File to delete * @param sftp
     */
    public String delete(String directory, String deleteFile, ChannelSftp sftp) {
        String result = "";
        try {
            sftp.cd(directory);
            sftp.rm(deleteFile);
            result = "Deleted successfully!";
        } catch (Exception e) {
            result = "Delete failed!";
            LOG.info("Delete failed!", e);
        }
        return result;
    }
 
    private void closeChannel(Channel channel) {
        if (channel != null) {
            if (channel.isConnected()) {
                channel.disconnect();
            }
        }
    }
 
    private void closeSession(Session session) {
        if (session != null) {
            if (session.isConnected()) {
                session.disconnect();
            }
        }
    }
 
    public void closeAll(ChannelSftp sftp, Channel channel, Session session) {
        try {
            closeChannel(sftp);
            closeChannel(channel);
            closeSession(session);
        } catch (Exception e) {
            LOG.info("closeAll", e);
        }
    }
}

import java.util.Random; 
public class IDUtils {
 
    /**
     * Generate a random picture name */
    public static String genImageName() {
        //Get the long integer value of the current time including milliseconds long millis = System.currentTimeMillis();       
        //Add three random numbers Random random = new Random();
        int end3 = random.nextInt(999);
        //If there are less than three digits, add 0 in front
        String str = millis + String.format("%03d", end3);        
        return str;
    }
}

@Log("Website case upload information")
@ResponseBody
@PostMapping("/upload")
@RequiresPermissions("common:cases:upload")
R upload(@RequestParam("file") MultipartFile file,@RequestParam("ctitle") String ctitle, @RequestParam("cmessage") String cmessage,
       @RequestParam("casetroduction") String casetroduction,@RequestParam("strdate") Date strdate,@RequestParam("stpdate") Date stpdate,
       @RequestParam("credate") Date credate,HttpServletRequest request) throws ParseException, IOException {
   String oldName = file.getOriginalFilename();
   //Use IDUtils tool class to generate a new file name, new file name = newName + file suffix String newName = IDUtils.genImageName();
   newName = newName + oldName.substring(oldName.lastIndexOf("."));
   SftpUtils ft = new SftpUtils();
   //Connect the parameters through SFtoInfo parameters Session s = ft.getSession(SFTPInfo.SFTP_REQ_HOST,SFTPInfo.SFTP_DEFAULT_PORT, SFTPInfo.SFTP_REQ_USERNAME,SFTPInfo.SFTP_REQ_PASSWORD);
   Channel channel = ft.getChannel(s);
   ChannelSftp sftp = (ChannelSftp)channel;
   Boolean upload = ft.uploadFile(sftp,SFTPInfo.basePath, file.getInputStream(),newName);
   if(upload){
      //Close the upload successfully ft.closeAll(sftp, channel, s); //Close the connection CasesDO cases=new CasesDO();
      cases.setCtitle(ctitle);
        // This is very important. This is the access path written into the database plus the online domain name to access the image. The blogger has added an SSL certificate here. // https://**.**.com/images newName=file name picture cases.setCaseimg(SFTPInfo.baseUrl + "/" + newName);
      cases.setCasetroduction(casetroduction);
      cases.setStpdate(stpdate);
      cases.setCredate(credate);
      cases.setStrdate(strdate);
      cases.setCmessage(cmessage);
      if (casesService.save(cases) > 0) {
         return R.ok("Upload successful");
      }
               }else {
      return R.error("upload error");
   }
   return R.error();
}

var clipboard = new Clipboard('button.copy', {
    text: function (trigger) {
        layer.msg('The file path has been copied to the clipboard');
        return $(trigger).attr('url');
    }
});
layui.use('upload', function () {
    var upload = layui.upload;
    //Execute the example upload.render({
        elem: '#test1', //Binding element url: '/common/cases/upload', //Upload interface size: 100000,
        // auto: false,
        accept: 'file',
        //bindAction: '#submits',
        before: function (obj) {
            //The information contained in the obj parameter is exactly the same as the choose callback. The input parameter layer.load() is transmitted to the background;
            this.data = {
                ctitle: $('#ctitle').val(),
                cmessage: $('#cmessage').val() ,
                casetroduction: $('#casetroduction').val()
                ,strdate: $('#strdate').val()
                ,stpdate: $('#stpdate').val()
                ,credate: $('#credate').val(),
            };
        },
        done: function (r) {
            parent.layer.msg(r.msg);
            parent.reLoad();
            var index = parent.layer.getFrameIndex(window.name); // Get window index parent.layer.close(index);
        },
        error: function (r) {
            layer.msg(r.msg);
        }
    });
});