Apache Mina SFTP: Mount Remote Sub-Directory instead of Filesystem Root - sftp

Question

I would to use Apache SSHD to create an SFTP server and use SftpFileSystemProvider to mount a remote directory.
I successfully create the virtual file system with SftpFileSystemProvider following the documentation https://github.com/apache/mina-sshd/blob/master/docs/sftp.md#using-sftpfilesystemprovider-to-create-an-sftpfilesystem.
However I'm stuck when mouting remote directory even with the documentation https://github.com/apache/mina-sshd/blob/master/docs/sftp.md#configuring-the-sftpfilesystemprovider. It keeps mouting the root directory instead of the target one.
I tried:
adding the target directory into the sftp uri (not working)
getting new filesystem from path (not working)
Here is a quick example.
object Main:
class Events extends SftpEventListener
class Auth extends PasswordAuthenticator {
override def authenticate(username: String, password: String, session: ServerSession): Boolean = {
true
}
}
class FilesSystem extends VirtualFileSystemFactory {
override def createFileSystem(session: SessionContext): FileSystem = {
val uri = new URI("sftp://xxx:yyy#host/plop")
// val uri = SftpFileSystemProvider.createFileSystemURI("host", 22, "xxx", "yyy")
val fs = Try(FileSystems.newFileSystem(uri, Collections.emptyMap[String, Object](), new SftpFileSystemProvider().getClass().getClassLoader())) match {
case Failure(exception) =>
println("Failed to mount bucket")
println(exception.getMessage)
throw exception
case Success(filesSystem) =>
println("Bucket mounted")
filesSystem
}
//fs.getPath("plop").getFileSystem
fs
}
}
private val fs = new FilesSystem()
private val sftpSubSystem = new SftpSubsystemFactory.Builder().build()
sftpSubSystem.addSftpEventListener(new Events())
private val sshd: SshServer = SshServer.setUpDefaultServer()
sshd.setPort(22)
sshd.setHost("0.0.0.0")
sshd.setSubsystemFactories(Collections.singletonList(sftpSubSystem))
sshd.setKeyPairProvider(new SimpleGeneratorHostKeyProvider(Paths.get("hostkey.ser")))
sshd.setShellFactory(new InteractiveProcessShellFactory())
sshd.setCommandFactory(new ScpCommandFactory())
sshd.setFileSystemFactory(fs)
sshd.setPasswordAuthenticator(new Auth())
sshd.setSessionHeartbeat(HeartbeatType.IGNORE, Duration.ofSeconds(30L))
#main def m() = {
sshd.start()
while (sshd.isStarted) {
}
}
end Main
Am I missing something ?
SSHD version 2.8.0, SFTP protocol version 3, Scala3, Java11

Answer 1

I could be wrong, but, I think that these two ...
sshd.setShellFactory(new InteractiveProcessShellFactory())
sshd.setCommandFactory(new ScpCommandFactory())
sshd.setFileSystemFactory(fs)
... are redundant and this ...
private val sftpSubSystem = new SftpSubsystemFactory.Builder().build()
... needs to be made aware of the virtual file system.