blog of itemis l.e.

public class BasicAuthHandler extends AbstractLoginDialog {
 
  private String username;
  private char[] password;
 
  protected Control createDialogArea(Composite parent) {
    // implement user interface
  }
 
  public void internalHandle() {
    Callback[] callbacks = getCallbacks();
    for (int i = 0; i < callbacks.length; i++) {
      if (callbacks[i] instanceof NameCallback) {
        ((NameCallback) callbacks[i]).setName(username);
      } else if (callbacks[i] instanceof PasswordCallback) {
        ((PasswordCallback) callbacks[i]).setPassword(password);
      }
    }
  }
}

public abstract class AbstractLoginDialog extends TitleAreaDialog
  implements CallbackHandler {
 
  Callback[] callbackArray;
 
  protected final Callback[] getCallbacks() {
    return this.callbackArray;
  }
 
  public abstract void internalHandle();
 
  public void handle(final Callback[] callbacks) throws IOException {
    this.callbackArray = callbacks;
    final Display display = Display.getDefault();
    display.syncExec(new Runnable() {
      public void run() {
        isCancelled = false;
        setBlockOnOpen(false);
        open();
 
        final Button okButton = getButton(IDialogConstants.OK_ID);
        okButton.setText("Login");
        okButton.addSelectionListener(new SelectionListener() {
 
          public void widgetSelected(final SelectionEvent event) {
            processCallbacks = true;
          }
 
          public void widgetDefaultSelected(final SelectionEvent event) {
            // nothing to do
          }
        });
 
        final Button cancel = getButton(IDialogConstants.CANCEL_ID);
        cancel.addSelectionListener(new SelectionListener() {
 
          public void widgetSelected(final SelectionEvent event) {
            isCancelled = true;
            processCallbacks = true;
          }
 
          public void widgetDefaultSelected(final SelectionEvent event) {
            // nothing to do
          }
        });
      }
    });
 
    try {
      ModalContext.setAllowReadAndDispatch(true);
      ModalContext.run(new IRunnableWithProgress() {
 
      public void run(final IProgressMonitor monitor) {
        // Wait here until OK or cancel is pressed, then let it rip.
        // The event listener is responsible for closing the dialog
        // (in the loginSucceeded event).
        while (!processCallbacks) {
          try {
            Thread.sleep(100);
          } catch (final Exception e) {
            // do nothing
          }
        }
        processCallbacks = false;
        // Call the adapter to handle the callbacks
        if (!isCancelled()) {
          internalHandle();
 
        }
      }, true, new NullProgressMonitor(), Display.getDefault());
    } catch (final Exception e) {
      final IOException ioe = new IOException();
      ioe.initCause(e);
      throw ioe;
    }
  }
  ...
}

package org.foo.bar;
 
public class Application implements IEntryPoint {
 
  public int createUI() {
    Display display = PlatformUI.createDisplay();
    if (login(display)) {
      WorkbenchAdvisor advisor = new ApplicationWorkbenchAdvisor();
      return PlatformUI.createAndRunWorkbench(display, advisor);
    }
    return 0;
  }
 
  private boolean login(final Display display) {
    String configName = "MyLogin";
    URL configUrl = Activator.getDefault().getBundle()
                     .getEntry("data/jaas_config.txt");
    ILoginContext secureContext = LoginContextFactory
                     .createContext(configName, configUrl);
 
    Subject s = null;
    do {
      try {
        s = secureContext.getSubject();
      } catch (LoginException e) {
        // handle login exception
      }
    } while (s == null);
    return true;
  }
}