We have created our own custom principal class by implementing the java.security.Principal interface. It's a very simple class in which we take in the username through a constructor and then use that to return in the getName method:

public class JaasPrincipal implements Principal, Serializable {
    private String username;
    public JaasPrincipal(String username) {
        this.username = username;
    }
    @Override
    public String getName() {
        return "Authenticated_"+this.username;
    }
}