How to call CallbackHandler to input user name and password?

Question

Hello,
I am new to CallbackHandlers. I wrote a small Swing application. I want this Swing application to display a login page so that user can enter user name and password, and then provide this to my CallbackHandler class.
Here is what I did in my Swing main method
    public static void main(String[] args) {
        try {           
            LoginContext lc = new LoginContext("Login",
                    new MyCallbackHandler());
            lc.login();
            UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
            new TestCVTApplication();
..Here is what I did in my CallbackHandler
public class MyCallbackHandler implements javax.security.auth.callback.CallbackHandler {
    private String username;
    private String password;
    public MyCallbackHandler() {
    public void handle(Callback[] callbacks) throws java.io.IOException, UnsupportedCallbackException {       
        for (int i = 0; i < callbacks.length; i++) {
            if(callbacks[i] instanceof NameCallback){
                NameCallback ncb = (NameCallback)callbacks;
ncb.setName(username);
if(callbacks[i] instanceof PasswordCallback){
PasswordCallback pcb = (PasswordCallback)callbacks[i];
pcb.setPassword(password.toCharArray());
Would you let me know what I am missing?
Thanks,
Mustafa                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           

Answer 1

The code you posted never assigns values to the private username and password fields of the MyCallbackHandler class. So when its handle method is invoked it simply assigns nulls to the values in the callback objects.
Or is there code elsewhere you did not show? Are you certain that your callback is invoked at all?
- Tim