SFTP server multiple user authentication

I am trying to extend the user authentication example, which is also presented here, so that multiple users can login to the server. I would also like to assign a different home directory for each user. So far, I haven't been able to find any such utility provided by the Apache SSHD API, so I have tried the following workaround, by using the utilities provided by the Apache FtpServer.

What I attempt to do is:

1. create a UserManager object to manage a list of users and store their information in a property file, in a way similar to this example

2. create a PasswordAuthenticator that makes use of the UserManager in its authenticate method, as follows:

   public class MyPasswordAuthenticator implements PasswordAuthenticator {
   
       private UserManager userManager;
   
       public MyPasswordAuthenticator(){
           this.userManager=null;
       }
   
       public MyPasswordAuthenticator(UserManager manager) {
           this.userManager=manager;
       }
   
       @Override
       public boolean authenticate(String username, String password, ServerSession session) throws PasswordChangeRequiredException {
           if (this.userManager==null) return false;
           User usr=null;
           try {
               usr = userManager.getUserByName(username);
           } catch (FtpException e) {
               e.printStackTrace();
           }
           if (usr==null) return false;
           else{       
               String pass=usr.getPassword();
               return password.equals(pass);
           }
       }
   
   
   }
   

However, the usr.getPassword() returns null, even though a) the password fields in the property file do have values b) I have checked the functions getName() and getHomeDirectory() and they return their respective String values.

My question is, why does this happen and what should be done to fix this?

I have found a way to make it work, it is:

usr = this.userManager.authenticate(new UsernamePasswordAuthentication(username, password));