Lots of exceptions in a simple JavaFX programm that implements a window with a lable and a button

Question

I have the classes and fxml files in the same package application and when I try to run one of the controller classes (AnwendungsController.java) which calls the fxml file (Anwendung.fxml), I get the following errors:

Exception in Application start method
java.lang.reflect.InvocationTargetException
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
    at java.lang.reflect.Method.invoke(Unknown Source)
    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(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
    at java.lang.reflect.Method.invoke(Unknown Source)
    at sun.launcher.LauncherHelper$FXHelper.main(Unknown Source)
Caused by: java.lang.RuntimeException: Exception in Application start method
    at com.sun.javafx.application.LauncherImpl.launchApplication1(LauncherImpl.java:917)
    at com.sun.javafx.application.LauncherImpl.lambda$launchApplication$155(LauncherImpl.java:182)
    at java.lang.Thread.run(Unknown Source)
Caused by: javafx.fxml.LoadException: 
/D:/sciebo/Development/EclipseWorkspace/OOSP4%20(JavaFX)/bin/application/Anwendung.fxml:10

    at javafx.fxml.FXMLLoader.constructLoadException(FXMLLoader.java:2601)
    at javafx.fxml.FXMLLoader.access$700(FXMLLoader.java:103)
    at javafx.fxml.FXMLLoader$ValueElement.processAttribute(FXMLLoader.java:922)
    at javafx.fxml.FXMLLoader$InstanceDeclarationElement.processAttribute(FXMLLoader.java:971)
    at javafx.fxml.FXMLLoader$Element.processStartElement(FXMLLoader.java:220)
    at javafx.fxml.FXMLLoader$ValueElement.processStartElement(FXMLLoader.java:744)
    at javafx.fxml.FXMLLoader.processStartElement(FXMLLoader.java:2707)
    at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:2527)
    at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:2441)
    at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3214)
    at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3175)
    at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3148)
    at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3124)
    at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3104)
    at javafx.fxml.FXMLLoader.load(FXMLLoader.java:3097)
    at application.AnwendungsController.start(AnwendungsController.java:25)
    at com.sun.javafx.application.LauncherImpl.lambda$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)
    at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
    at com.sun.glass.ui.win.WinApplication.lambda$null$148(WinApplication.java:191)
    ... 1 more
Caused by: java.lang.ClassNotFoundException: AnwendungsController
    at java.net.URLClassLoader.findClass(Unknown Source)
    at java.lang.ClassLoader.loadClass(Unknown Source)
    at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
    at java.lang.ClassLoader.loadClass(Unknown Source)
    at javafx.fxml.FXMLLoader$ValueElement.processAttribute(FXMLLoader.java:920)
    ... 22 more
Exception running application application.AnwendungsController

AnwendungsController.java:

package application;

import javafx.application.Application;
import javafx.event.ActionEvent;
import javafx.fxml.FXML;
import javafx.fxml.FXMLLoader;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.stage.Stage;

public class AnwendungsController extends Application {

  @FXML
  public Button closeButton;

  @FXML
  public void handleCloseButtonAction(ActionEvent event) {
    Stage stage = (Stage) closeButton.getScene().getWindow();
    stage.close();
  }

  @Override
  public void start(Stage primaryStage) throws Exception {
    Parent root = FXMLLoader.load(getClass().getResource("Anwendung.fxml"));
    primaryStage.setTitle("Benutzerverwaltung");
    primaryStage.setScene(new Scene(root));
    primaryStage.show();
  }

  public static void main(String[] args) {
    launch(args);
  }
}

Anwendung.fxml:

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

<?import javafx.geometry.Insets?>
<?import javafx.scene.layout.GridPane?>
<?import javafx.scene.control.Button?>
<?import javafx.scene.control.Label?>

<GridPane  fx:controller="AnwendungsController.Controller" 
    xmlns:fx="http://javafx.com/fxml" alignment="center"
    hgap="10" vgap="10">
    <padding>
        <Insets top="20" right="20" bottom="20" left="20" />
    </padding>
    <Label text="Sie können das System nun verwenden!"
        GridPane.rowIndex="0" />
    <Button text="Abbrechen" fx:id="closeButton" cancelButton="true" mnemonicParsing="false" onAction="#handleCloseButtonAction" GridPane.rowIndex="1" />
</GridPane>

score 2 · Accepted Answer · edited May 23 '17 at 12:13

Solution

Your fx:controller attribute has the wrong value. The value should reflect the fully qualified name (package.class) of your controller class. Your package is named application and your controller class is named AnwendungsController.

Instead of:

fx:controller="AnwendungsController.Controller"

Use:

fx:controller="application.AnwendungsController"

Additional Advice

Additionally, your application class should not also be a controller class as doing so will likely cause you a world of unnecessary pain. There should be no @FXML injected variables in an application class. See: Javafx - Can application class be the controller class.

Restructured App

application/Anwendung.fxml

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

<?import javafx.geometry.Insets?>
<?import javafx.scene.layout.GridPane?>
<?import javafx.scene.control.Button?>
<?import javafx.scene.control.Label?>

<GridPane  fx:controller="application.AnwendungsController"
           xmlns:fx="http://javafx.com/fxml" alignment="center"
           hgap="10" vgap="10">
  <padding>
    <Insets top="20" right="20" bottom="20" left="20" />
  </padding>
  <Label text="Sie können das System nun verwenden!"
         GridPane.rowIndex="0" />
  <Button text="Abbrechen" fx:id="closeButton" cancelButton="true" mnemonicParsing="false" onAction="#handleCloseButtonAction" GridPane.rowIndex="1" />
</GridPane>

application/AnwendungsApp.java

package application;

import javafx.application.Application;
import javafx.fxml.FXMLLoader;
import javafx.scene.*;
import javafx.stage.Stage;

public class AnwendungsApp extends Application {
  @Override
  public void start(Stage primaryStage) throws Exception {
    FXMLLoader loader = new FXMLLoader(getClass().getResource("Anwendung.fxml"));
    Parent root = loader.load();
    primaryStage.setTitle("Benutzerverwaltung");
    primaryStage.setScene(new Scene(root));
    primaryStage.show();
  }

  public static void main(String[] args) {
    launch(args);
  }
}

application/AnwendungsController.java

package application;

import javafx.event.ActionEvent;
import javafx.fxml.FXML;
import javafx.scene.control.Button;
import javafx.stage.Stage;

public class AnwendungsController {
  @FXML
  public Button closeButton;

  @FXML
  public void handleCloseButtonAction(ActionEvent event) {
    Stage stage = (Stage) closeButton.getScene().getWindow();
    stage.close();
  }
}

[Intellij Idea](https://www.jetbrains.com/idea/) performs spell checking on FXML as well as inspections which would highlight in red things such as the incorrect `fx:controller` value shown in your original question. You might need to use the Ultimate edition to get the inspection highlighting (I'm not sure). Ultimate edition has a free trial. There are probably other tools which also perform inspections, such as [e(fx)clipse](http://www.eclipse.org/efxclipse/index.html) or maybe [netbeans](https://netbeans.org). From my experience, Idea does a reasonable job. — jewelsea, Dec 02 '16 at 22:24

Lots of exceptions in a simple JavaFX programm that implements a window with a lable and a button

1 Answers1