Я использую Apache Commons FTP для загрузки файла. Перед загрузкой я хочу проверить, существует ли файл на сервере, и сделать из него резервную копию в каталог резервных копий на том же сервере.

Does anyone know how to copy a file from a FTP server to a backup directory on the same server?

public static void uploadWithCommonsFTP(File fileToBeUpload){
    FTPClient f = new FTPClient();
    FTPFile backupDirectory;
    try {
        f.connect(server.getServer());
        f.login(server.getUsername(), server.getPassword());
        FTPFile[] directories = f.listDirectories();
        FTPFile[] files = f.listFiles();
        for(FTPFile file:directories){
            if (!file.getName().equalsIgnoreCase("backup")) {
                backupDirectory=file;
            } else {
               f.makeDirectory("backup");
            }
        }
        for(FTPFile file: files){
            if(file.getName().equals(fileToBeUpload.getName())){
                //copy file to backupDirectory
            }
        }

    } catch (IOException e) {
        e.printStackTrace();
    }

}

Edited code: Тем не менее, существует проблема, когда я делаю резервную копию zip файла, файл резервной копии поврежден.

Does any body know the reason for it?

 public static void backupUploadWithCommonsFTP(File fileToBeUpload) {
    FTPClient f = new FTPClient();
    boolean backupDirectoryExist = false;
    boolean fileToBeUploadExist = false;
    FTPFile backupDirectory = null;
    try {
        f.connect(server.getServer());
        f.login(server.getUsername(), server.getPassword());
        FTPFile[] directories = f.listDirectories();
        // Check for existence of backup directory
        for (FTPFile file : directories) {
            String filename = file.getName();
            if (file.isDirectory() && filename.equalsIgnoreCase("backup")) {
                backupDirectory = file;
                backupDirectoryExist = true;
                break;
            }
        }
        if (!backupDirectoryExist) {
            f.makeDirectory("backup");
        }
        // Check if file already exist on the server
        f.changeWorkingDirectory("files");
        FTPFile[] files = f.listFiles();
        f.changeWorkingDirectory("backup");
        String filePathToBeBackup="/home/user/backup/";
        String prefix;
        String suffix;
        String fileNameToBeBackup;
        FTPFile fileReadyForBackup = null;
        f.setFileType(FTP.BINARY_FILE_TYPE);
        f.setFileTransferMode(FTP.BINARY_FILE_TYPE);
        for (FTPFile file : files) {
            if (file.isFile() && file.getName().equals(fileToBeUpload.getName())) {
                prefix = FilenameUtils.getBaseName(file.getName());
                suffix = ".".concat(FilenameUtils.getExtension(file.getName()));
                fileNameToBeBackup = prefix.concat(Calendar.getInstance().getTime().toString().concat(suffix));
                filePathToBeBackup = filePathToBeBackup.concat(fileNameToBeBackup);
                fileReadyForBackup = file;
                fileToBeUploadExist = true;
                break;
            }
        }
        // If file already exist on the server create a backup from it otherwise just upload the file.
        if(fileToBeUploadExist){
            ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
            f.retrieveFile(fileReadyForBackup.getName(), outputStream);
            InputStream is = new ByteArrayInputStream(outputStream.toByteArray());
            if(f.storeUniqueFile(filePathToBeBackup, is)){
                JOptionPane.showMessageDialog(null, "Backup succeeded.");
                f.changeWorkingDirectory("files");
                boolean reply = f.storeFile(fileToBeUpload.getName(), new FileInputStream(fileToBeUpload));
                if(reply){
                    JOptionPane.showMessageDialog(null,"Upload succeeded.");
                }else{
                    JOptionPane.showMessageDialog(null,"Upload failed after backup.");
                }
            }else{
                JOptionPane.showMessageDialog(null,"Backup failed.");
            }
        }else{
            f.changeWorkingDirectory("files");
            f.setFileType(FTP.BINARY_FILE_TYPE);
            f.enterLocalPassiveMode();
            InputStream inputStream = new FileInputStream(fileToBeUpload);
            ByteArrayInputStream in = new ByteArrayInputStream(FileUtils.readFileToByteArray(fileToBeUpload));
            boolean reply = f.storeFile(fileToBeUpload.getName(), in);
            System.out.println("Reply code for storing file to server: " + reply);
            if(!f.completePendingCommand()) {
                f.logout();
                f.disconnect();
                System.err.println("File transfer failed.");
                System.exit(1);
            }
            if(reply){

                JOptionPane.showMessageDialog(null,"File uploaded successfully without making backup." +
                        "\nReason: There wasn't any previous version of this file.");
            }else{
                JOptionPane.showMessageDialog(null,"Upload failed.");
            }
        }
        //Logout and disconnect from server
        in.close();
        f.logout();
        f.disconnect();
    } catch (IOException e) {
        e.printStackTrace();
    }

}