Apparently any control that inherits from TextInputControl has an issue when it has a TextFormatter that contains a StringConverter which has a toString() method that returns null (for example when the input value is null).

This raises a NullPointerException in the method private <T> void updateText(TextFormatter<T> formatter) in the class TexInputControl because the value returned from converter.toString() is not checked before calling replaceText(). As of now the code for this method is as follows in TextInputControl:

    private <T> void updateText(TextFormatter<T> formatter) {
        T value = formatter.getValue();
        StringConverter<T> converter = formatter.getValueConverter();
        if (converter != null) {
            String text = converter.toString(value);
            replaceText(0, getLength(), text, text.length(), text.length());
        }
    }

The documentation from StringConverter.toString() does not specify if null is an illegal value or not.

A way to circumvent the issue is to return the empty string ("") instead of null.

The issue arose to me while doing a TextFormatter for a spinner that allows people to enter a port value. The value of the spinner is initially null in order to let the user see the prompt text.

Value factory for the Spinner:

public final class PortValueFactory extends SpinnerValueFactory<Integer> {

    @Override
    public void decrement(int steps) {
        final Integer value = getValue();
        final int nextValue = (value == null) ? PortTextFormatter.MIN_PORT : Math.max(value - 1, PortTextFormatter.MIN_PORT);
        setValue(nextValue);
    }

    @Override
    public void increment(int steps) {
        final Integer value = getValue();
        final int nextValue = (value == null) ? PortTextFormatter.MIN_PORT : Math.min(value + 1, PortTextFormatter.MAX_PORT);
        setValue(nextValue);
    }
}

Textformatter for the Spinner's editor:

public final class PortTextFormatter extends TextFormatter<Integer> {

    /**
     * The min port value.
     */
    public static final int MIN_PORT = 0;
    /**
     * The max port value.
     */
    public static final int MAX_PORT = 2 * Short.MAX_VALUE + 1;

    /**
     * Creates a new instance.
     */
    public PortTextFormatter() {
// super(Converter.getInstance(), null, Filter.getInstance());
        super(Converter.getInstance(), null, null);
    }

    /**
     * A filter that only accept short values that are valid for a port.
     * @author Fabrice Bouyé (fabriceb@spc.int)
     */
    public final static class Filter implements UnaryOperator<TextFormatter.Change> {

        /**
         * The unique instance of this class.
         */
        private static Filter INSTANCE;

        /**
         * Hidden constructor.
         */
        private Filter() {
        }

        @Override
        public TextFormatter.Change apply(TextFormatter.Change change) {
            final String text = change.getText();
            TextFormatter.Change result = (text.isEmpty() || text.matches("[0-9]+")) ? change : null; // NOI18N.
            try {
                final int value = Integer.parseInt(change.getControlNewText());
                if (value < MIN_PORT || value > MAX_PORT) {
                    result = null;
                }
            } catch (NumberFormatException ex) {
// MOViTLogger.LOGGER.log(Level.FINEST, ex.getMessage(), ex);
            }
            return result;
        }

        /**
         * Gets the unique instance of this class.
         * @return The unique instance of this class.
         */
        public synchronized static Filter getInstance() {
            if (INSTANCE == null) {
                INSTANCE = new Filter();
            }
            return INSTANCE;
        }
    }

    /**
     * A converter that only accept short values that are valid for a port.
     * @author Fabrice Bouyé (fabriceb@spc.int)
     */
    public final static class Converter extends StringConverter<Integer> {

        /**
         * The unique instance of this class.
         */
        private static Converter INSTANCE;

        /**
         * Hidden constructor.
         */
        private Converter() {
        }

        @Override
        public String toString(final Integer value) {
            final Integer val = (value == null) ? null : Math.max(MIN_PORT, Math.min(MAX_PORT, value));
// return (val == null) ? "" : val.toString();
            return (val == null) ? null : val.toString();
        }

        @Override
        public Integer fromString(final String text) {
            Integer result = (text == null || text.trim().isEmpty()) ? null : Integer.parseInt(text.trim());
            result = (result == null) ? MIN_PORT : Math.max(MIN_PORT, Math.min(MAX_PORT, result));
            return result;
        }

        /**
         * Gets the unique instance of this class.
         * @return The unique instance of this class.
         */
        public synchronized static Converter getInstance() {
            if (INSTANCE == null) {
                INSTANCE = new Converter();
            }
            return INSTANCE;
        }
    }
}

Test code:

public class Main extends Application {

    @Override
    public void start(Stage primaryStage) {
        Spinner<Integer> spinner = new Spinner();
        spinner.setValueFactory(new PortValueFactory());
        spinner.getEditor().setTextFormatter(new PortTextFormatter());
        StackPane root = new StackPane();
        root.getChildren().add(spinner);
        Scene scene = new Scene(root, 300, 250);
        primaryStage.setTitle("Test");
        primaryStage.setScene(scene);
        primaryStage.show();
    }

    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {
        launch(args);
    }
}

Upon launch the following exception is raised:

java.lang.reflect.InvocationTargetException
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:497)
at com.sun.javafx.application.LauncherImpl.launchApplicationWithArgs(LauncherImpl.java:389)
at com.sun.javafx.application.LauncherImpl.launchApplication(LauncherImpl.java:328)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:497)
at sun.launcher.LauncherHelper$FXHelper.main(LauncherHelper.java:767)
Caused by: java.lang.RuntimeException: Exception in Application start method
at com.sun.javafx.application.LauncherImpl.launchApplication1(LauncherImpl.java:917)
at com.sun.javafx.application.LauncherImpl.lambda$launchApplication$152(LauncherImpl.java:182)
at com.sun.javafx.application.LauncherImpl$$Lambda$50/1642360923.run(Unknown Source)
at java.lang.Thread.run(Thread.java:745)
Caused by: java.lang.NullPointerException
at javafx.scene.control.TextInputControl.updateText(TextInputControl.java:1215)
at javafx.scene.control.TextInputControl.access$300(TextInputControl.java:79)
at javafx.scene.control.TextInputControl$5.invalidated(TextInputControl.java:320)
at javafx.beans.property.ObjectPropertyBase.markInvalid(ObjectPropertyBase.java:111)
at javafx.beans.property.ObjectPropertyBase.set(ObjectPropertyBase.java:146)
at javafx.scene.control.TextInputControl.setTextFormatter(TextInputControl.java:334)
at test.Main.start(Main.java:20)
at com.sun.javafx.application.LauncherImpl.lambda$launchApplication1$159(LauncherImpl.java:863)
at com.sun.javafx.application.LauncherImpl$$Lambda$53/1379051502.run(Unknown Source)
at com.sun.javafx.application.PlatformImpl.lambda$runAndWait$172(PlatformImpl.java:326)
at com.sun.javafx.application.PlatformImpl$$Lambda$45/355629945.run(Unknown Source)
at com.sun.javafx.application.PlatformImpl.lambda$null$170(PlatformImpl.java:295)
at com.sun.javafx.application.PlatformImpl$$Lambda$48/1675761123.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at com.sun.javafx.application.PlatformImpl.lambda$runLater$171(PlatformImpl.java:294)
at com.sun.javafx.application.PlatformImpl$$Lambda$47/1915503092.run(Unknown Source)
at com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:95)
at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
at com.sun.glass.ui.win.WinApplication.lambda$null$145(WinApplication.java:101)
at com.sun.glass.ui.win.WinApplication$$Lambda$36/1963387170.run(Unknown Source)
... 1 more
Exception running application test.Main

This can be fixed by returning "" instead of null in the toString() method of the StringConverter wihtin the TextFormatter.