javafx i18n: "No resources specified" exception

Question

I am learning i18n for my javafx application.

Files:

java/
--LoginScreen.java
resources/
--login.fxml
--login_en.properties
--login_ru.properties

LoginScreen.java

@Override
public void start(Stage primaryStage) throws Exception
{
    URL url = getClass().getClassLoader().getResource("login.fxml");

    if (url == null)
    {
        System.err.println("Unable to load UI file.");
        return;
    }

    FXMLLoader loader = new FXMLLoader();
    String localeStr = "en"; //TODO: actual language selection
    loader.setResources(ResourceBundle.getBundle("login", new Locale(localeStr)));
    Parent root = loader.load(url);
    Scene scene = new Scene(root);
    primaryStage.setScene(scene);
    primaryStage.show();
}

login.fxml

<?xml version="1.0" encoding="UTF-8"?>

<?import javafx.scene.control.Label?>
<?import javafx.scene.control.TextField?>
<?import javafx.scene.control.PasswordField?>
<?import javafx.scene.layout.VBox?>

<VBox prefHeight="400.0" prefWidth="600.0" xmlns="http://javafx.com/javafx/8.0.121" xmlns:fx="http://javafx.com/fxml/1" fx:controller="app.LoginScreen">
    <Label text="%label_User" />
    <TextField fx:id="textField_user" />
    <Label text="%label_Password" />
    <PasswordField fx:id="passwordField_password" />
</VBox>

login_en.preperties:

label_User=User:
label_Password=Password:

login_ru.properties:

label_User=Пользователь:
label_Password=Пароль:

I am getting the following exception then it tries to execute Parent root = loader.load(url)

Exception in Application start method
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:498)
    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:498)
    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$155(LauncherImpl.java:182)
    at java.lang.Thread.run(Thread.java:745)
Caused by: javafx.fxml.LoadException: No resources specified.
/Users/user/Documents/javafx/build/resources/main/login.fxml:9

    at javafx.fxml.FXMLLoader.constructLoadException(FXMLLoader.java:2597)
    at javafx.fxml.FXMLLoader.access$100(FXMLLoader.java:103)
    at javafx.fxml.FXMLLoader$Element.resolvePrefixedValue(FXMLLoader.java:421)
    at javafx.fxml.FXMLLoader$Element.processValue(FXMLLoader.java:363)
    at javafx.fxml.FXMLLoader$Element.processPropertyAttribute(FXMLLoader.java:325)
    at javafx.fxml.FXMLLoader$Element.processInstancePropertyAttributes(FXMLLoader.java:235)
    at javafx.fxml.FXMLLoader$ValueElement.processEndElement(FXMLLoader.java:767)
    at javafx.fxml.FXMLLoader.processEndElement(FXMLLoader.java:2823)
    at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:2532)
    at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:2441)
    at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3214)
    at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3175)
    at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3148)
    at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3124)
    at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3104)
    at javafx.fxml.FXMLLoader.load(FXMLLoader.java:3097)
    at app.LoginScreen.start(LoginScreen.java:52)
    at com.sun.javafx.application.LauncherImpl.lambda$launchApplication1$162(LauncherImpl.java:863)
    at com.sun.javafx.application.PlatformImpl.lambda$runAndWait$175(PlatformImpl.java:326)
    at com.sun.javafx.application.PlatformImpl.lambda$null$173(PlatformImpl.java:295)
    at java.security.AccessController.doPrivileged(Native Method)
    at com.sun.javafx.application.PlatformImpl.lambda$runLater$174(PlatformImpl.java:294)
    at com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:95)
Exception running application app.LoginScreen

I seems that it is unable to get localized strings from the resources but when I debug it I can definitely see that the loader loads resources correctly.

What am I missing cause I an unable to determine the error myself.

Answer 1

By passing the URL to the load method, you're invoking a static load method that doesn't have access to any data you assigned to the properties of the FXMLLoader instance. The statements

Parent root = loader.load(url);

and

Parent root = FXMLLoader.load(url);

compile to the same bytecode.

Pass the URL by passing it as constructor parameter or using the setLocation method instead and call the no-arg load method:

FXMLLoader loader = new FXMLLoader(url);
String localeStr = "en"; //TODO: actual language selection
loader.setResources(ResourceBundle.getBundle("login", new Locale(localeStr)));
Parent root = loader.load();

You could also do this without creating a FXMLLoader instance yourself by passing both parameters to a static load method:

String localeStr = "en";
Parent root = loader.load(url, ResourceBundle.getBundle("login", new Locale(localeStr)));