Dialog ResultConverter does not clear password field

Question

I'm currently working on a password manager. Before making any changes to a certain service, the program will ask the user for a password for authorization and then proceed to show the appropriate dialog, if the password is correct.

The issue that I'm having is that if I go through the cycle of putting in my password to make the change, click "ok", and then proceeding to make changes on the shown dialog, on the next turn if instead of putting the password when prompted I close the prompt, then the program retrieves the password from the previous iteration although it has been explicitly cleared. Resulting in the concurrent dialog showing, which is only supposed to show if you put in the correct password.

private void handleEditButton(MouseEvent event) {
        Optional<String> rslt = passwordConfirmDialog.showAndWait();

        if (rslt.get().equals("")) 
            return; //Do not proceed

        String userInput = rslt.get().trim();

        // Complex expression, but use of && statement is necessary to avoid an
        // unecessary call to db and have return statement on this IF
        if (!(!userInput.isBlank() && isCorrectPassword(userInput))) {
            // show dialog
            AlertConfigs.invalidPasswordTransactionFailed.showAndWait();
            return;
        }

        System.out.println("Edit Handler: Correct password. -> " + userInput);

        //Proceed to show next dialog...

private void initializePasswordConfirmDialog() {

        passwordConfirmDialog.setTitle("User Account Control");
        passwordConfirmDialog.setHeaderText("Please enter your password to continue.");

        // Set the button types.
        ButtonType ok = new ButtonType("Ok", ButtonData.OK_DONE);
        passwordConfirmDialog.getDialogPane().getButtonTypes().addAll(ok, ButtonType.CANCEL);

        final PasswordField psField = new PasswordField();

        GridPane grid = new GridPane();

        grid.setHgap(10);
        grid.setVgap(10);
        grid.setPadding(new Insets(20, 150, 10, 10));

        grid.add(new Label("Please Enter your password"), 0, 0);
        grid.add(psField, 1, 0);

        passwordConfirmDialog.getDialogPane().setContent(grid);

        passwordConfirmDialog.setResultConverter(buttonType -> {

            String rslt = "";
            if (buttonType == ok) {
                rslt = psField.getText();
            }
           
            psField.clear();
            return rslt;
        });
    }

I've posted a video on YouTube to help visualize the problem. https://youtu.be/sgayh7Q7Ne8

The PasswordField in initializePasswordConfirmDialog() is cleared because whenever I run the the prompt the second time, the PasswordField is blank (visually). Nevertheless, for some reason it still grabs the result from the previous iteration.

The initializePasswordConfirmDialog() is called once inside the constructor and is responsible for set the passwordConfirmDialog variable with the adequate properties.

Some additional code:

 HomeController.java
    @FXML
    private GridPane servicesGrid;

    private Dialog<String> passwordConfirmDialog;
    private Dialog<Service> editServiceDialog;

    private final int NUM_COLUMNS = 7;

    public HomeController() {

        passwordConfirmDialog = new Dialog<>();
        initializePasswordConfirmDialog();

        editServiceDialog = new Dialog<>();

    }

    @Override
    public void initialize(URL arg0, ResourceBundle arg1) {
        loadServicesGridpane();
    }
    private void loadServicesGridpane() {
        ArrayList<Service> currS = acct.getServices();
        // int currentRow = 1;

        for (Service s : currS)
            addRowToServiceGrid(s);

    }

    private void addRowToServiceGrid(Service s) {
        int rowIdx = servicesGrid.getChildren().size() / 4;

        Button editButton = new Button("Edit");
        editButton.setOnMouseClicked(event -> {
            handleEditButton(event);
        });

       
        Button deleteButton = new Button("Delete");

        deleteButton.setOnMouseClicked(event -> {
            handleDeleteButton(event);
        });

        deleteButton.setId(s.getServiceName());

        Label currServiceName = new Label(s.getServiceName());
        currServiceName.setId(s.getServiceName());

        Label currUsername = new Label(s.getServiceUsername());

        Label currPassword = new Label(s.getServicePassword());

        Label dateCreated = new Label(s.getDateCreated());
        Label lastPssdChange = new Label(s.getLastPasswordChange());

        servicesGrid.addRow(rowIdx, currServiceName, currUsername, currPassword, dateCreated, lastPssdChange,
                deleteButton, editButton);

    }

Answer 1

To study the problem in isolation, I refactored this example to permit reusing the dialog. As shown below, reusing the dialog requires clearing the password field. Replace the parameter dialog with an invocation of createDialog() to see that creating the dialog each time does not require clearing the password field. Comparing the profile of each approach may help you decide which approach is acceptable; in my experiments, reuse added negligible memory overhead (~250 KB), and it protracted garbage collection slightly(~50 ms).

#!/bin/sh
java … DialogTest -reuse &
pid1=$!
java … DialogTest -no-reuse &
pid2=$!
echo $pid1 $pid2
jconsole $pid1 $pid2

Unfortunately, creating the dialog each time may only appear to solve the problem; it may have exposed a latent synchronization problem. In particular, verify that your result converter's callback executes on the JavaFX Application Thread. To illustrate, I've added a call to Platform.isFxApplicationThread() in resultsNotPresent() below.

import javafx.application.Application;
import javafx.application.Platform;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.ButtonType;
import javafx.scene.control.Dialog;
import javafx.scene.control.Label;
import javafx.scene.control.PasswordField;
import javafx.scene.control.TextField;
import javafx.scene.layout.HBox;
import javafx.scene.layout.VBox;
import javafx.stage.Stage;

/**
 * @see https://stackoverflow.com/q/73328282/230513
 * @see https://stackoverflow.com/a/44172143/230513
 */
public class DialogTest extends Application {

    private static boolean REUSE_DIALOG = true;

    private record Results(String text, String pass) {

        private static Results of(String text, String pass) {
            return new Results(text, pass);
        }
    }

    @Override
    public void start(Stage stage) {
        var label = new Label("Reuse: " + REUSE_DIALOG);
        var button = new Button("Button");
        if (REUSE_DIALOG) {
            var dialog = createDialog();
            button.setOnAction(e -> showDialog(dialog));
        } else {
            button.setOnAction(e -> showDialog(createDialog()));
        }
        stage.setScene(new Scene(new HBox(8, label, button)));
        stage.show();
    }

    private Dialog<Results> createDialog() {
        var dialog = new Dialog<Results>();
        dialog.setTitle("Dialog Test");
        dialog.setHeaderText("Please authenticate…");
        var dialogPane = dialog.getDialogPane();
        dialogPane.getButtonTypes().addAll(ButtonType.OK, ButtonType.CANCEL);
        var text = new TextField("Name");
        var pass = new PasswordField();
        dialogPane.setContent(new VBox(8, text, pass));
        dialog.showingProperty().addListener((o, wasShowing, isShowing) -> {
            if (isShowing) {
                Platform.runLater(pass::requestFocus);
            }
        });
        dialog.setResultConverter((ButtonType bt) -> {
            if (ButtonType.OK == bt) {
                var results = Results.of(text.getText(), pass.getText());
                pass.clear();
                return results;
            }
            pass.clear();
            return null;
        });
        return dialog;
    }

    private void showDialog(Dialog<Results> dialog) {
        var optionalResult = dialog.showAndWait();
        optionalResult.ifPresentOrElse(
            (var results) -> System.out.println(results),
            (this::resultsNotPresent));
    }

    private void resultsNotPresent() {
        System.out.println("Canceled on FX application thread: "
            + Platform.isFxApplicationThread());
    }

    public static void main(String[] args) {
        if (args.length > 0) {
            REUSE_DIALOG = args[0].startsWith("-r");
        }
        launch(args);
    }
}