SFTP transmission of content using apache VFS2 and OpenSSH private key

FileTransferScpImpl.java

@Component
public class FileTransferScpImpl {


    private final String userName;
    private final String hostName;
    private final FileSystemOptions opts;
    private final StandardFileSystemManager manager;
    private final String privateKeyPath;
    private final int timeout;

    /**
     * @param userName the user name in the remote host, davengeo
     * @param hostName the remote host, myhost.com
     * @param privateKeyPath the private key in openssh format, C:/Users/XXXXXX/.ssh/id_rsa.pem
     */
     @Autowired
    public FileTransferScpImpl(@Value("${sftp.username}") String userName,
                               @Value("${sftp.hostname}") String hostName,
                               @Value("${sftp.privateKey}") String privateKeyPath,
                               @Value("S{sftp.timeout}") int timeout) {
        this.userName = userName;
        this.hostName = hostName;
        this.privateKeyPath = privateKeyPath;
        this.timeout = timeout;
        opts = new FileSystemOptions();
        manager = new StandardFileSystemManager();
    }

    @PostConstruct
    public void init() throws FileSystemException {
        SftpFileSystemConfigBuilder.getInstance().setStrictHostKeyChecking(
                opts, "no");
        File[] identities = { new File(privateKeyPath) };
        SftpFileSystemConfigBuilder.getInstance().setIdentities(opts, identities);
        SftpFileSystemConfigBuilder.getInstance().setUserDirIsRoot(opts, true);
        SftpFileSystemConfigBuilder.getInstance().setTimeout(opts, timeout);
        manager.init();
    }

    public Observable<String> getStream(final String filename) {
        return Observable.create(new Observable.OnSubscribe<String>() {
            @Override
            public void call(Subscriber<? super String> subscriber) {
                try {
                    subscriber.onNext(getContentOf(filename);
                    subscriber.onCompleted();
                } catch (IOException e) {
                    subscriber.onError(e);
                }
            }
        });
    }

    public String getContentOf(String filename) throws IOException {
        String sftpUri = formatUri(filename);
        FileObject remoteFile = manager.resolveFile(sftpUri, opts);
        return IOUtils.toString(remoteFile.getContent().getInputStream());
    }

    public void sendDataTo(String filename, String content) throws IOException {
        String sftpUri = formatUri(filename);
        writeInLocal(filename, content);
        LocalFile localFile = getLocalFile(filename);
        FileObject remoteFile = manager.resolveFile(sftpUri, opts);
        remoteFile.copyFrom(localFile, Selectors.SELECT_SELF);
        closeAndDelete(localFile);
    }

    private String formatUri(String filename) {
        return String.format("sftp://%s@%s/%s", userName, hostName, filename);
    }

    private LocalFile getLocalFile(String filename) throws FileSystemException {
        File file = new File(filename);
        return (LocalFile) manager.resolveFile(file.getAbsolutePath());
    }

    private void writeInLocal(String filename, String content) throws IOException {
        FileWriter fileWriter = new FileWriter(filename);
        fileWriter.write(content);
        fileWriter.close();
    }

    private void closeAndDelete(LocalFile localFile) throws FileSystemException {
        localFile.close();
        localFile.delete();
    }

}