Javafx error exception in Application start method

Question

When I run the following code in intellij with java 8 I get an error. Please Help. The fxml is generated using the scene builder, I think the button Dagrooster isn't linked with the method.

package Weert;

import javafx.application.Application;
import javafx.fxml.FXMLLoader;
 import javafx.scene.Parent;
 import javafx.scene.Scene;
import javafx.stage.Stage;

public class Main extends Application {

@Override
public void start(Stage primaryStage) throws Exception{
    Parent root = FXMLLoader.load(getClass().getResource("Weert.fxml"));
    primaryStage.setTitle("test");
    primaryStage.setScene(new Scene(root, 300, 275));
    primaryStage.show();
}


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

Weert.fxml:

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

<?import javafx.scene.web.*?>
<?import javafx.scene.control.*?>
<?import java.lang.*?>
<?import javafx.scene.layout.*?>
<?import javafx.geometry.Insets?>
<?import javafx.scene.layout.GridPane?>
<?import javafx.scene.control.Button?>
<?import javafx.scene.control.Label?>

<BorderPane maxHeight="1.7976931348623157E308" maxWidth="1.7976931348623157E308" prefHeight="400.0" prefWidth="600.0" xmlns="http://javafx.com/javafx/8" xmlns:fx="http://javafx.com/fxml/1">
   <top>
      <GridPane alignment="TOP_CENTER" BorderPane.alignment="CENTER">
        <columnConstraints>
          <ColumnConstraints halignment="CENTER" hgrow="SOMETIMES" minWidth="10.0" prefWidth="100.0" />
          <ColumnConstraints halignment="CENTER" hgrow="SOMETIMES" minWidth="10.0" prefWidth="100.0" />
            <ColumnConstraints halignment="CENTER" hgrow="SOMETIMES" minWidth="10.0" prefWidth="100.0" />
        </columnConstraints>
        <rowConstraints>
          <RowConstraints minHeight="10.0" prefHeight="30.0" vgrow="SOMETIMES" />
        </rowConstraints>
         <children>
            <Button fx:id="btnDagrooster" alignment="TOP_CENTER" contentDisplay="CENTER" maxWidth="1.7976931348623157E308" mnemonicParsing="false" onAction="#Dagrooster" text="Dagrooster" textAlignment="CENTER" GridPane.columnIndex="0" />
            <Button fx:id="btnHuidigRooster" alignment="TOP_CENTER" contentDisplay="CENTER" maxWidth="1.7976931348623157E308" mnemonicParsing="false" text="Huidig Rooster" textAlignment="CENTER" GridPane.columnIndex="1" />
            <Button fx:id="btnNieuwRooster" alignment="TOP_CENTER" contentDisplay="CENTER" maxWidth="1.7976931348623157E308" mnemonicParsing="false" text="Nieuw Rooster" textAlignment="CENTER" GridPane.columnIndex="2" />
         </children>
      </GridPane>
   </top>
   <bottom>
      <GridPane BorderPane.alignment="CENTER">
        <columnConstraints>
          <ColumnConstraints hgrow="SOMETIMES" minWidth="10.0" prefWidth="100.0" />
          <ColumnConstraints hgrow="SOMETIMES" minWidth="10.0" prefWidth="100.0" />
        </columnConstraints>
        <rowConstraints>
          <RowConstraints minHeight="10.0" prefHeight="30.0" vgrow="SOMETIMES" />
        </rowConstraints>
         <children>
            <Button alignment="TOP_CENTER" contentDisplay="CENTER" maxWidth="1.7976931348623157E308" mnemonicParsing="false" text="Instellingen" textAlignment="CENTER" />
            <Button alignment="TOP_CENTER" contentDisplay="CENTER" layoutX="10.0" layoutY="13.0" maxWidth="1.7976931348623157E308" mnemonicParsing="false" text="Laden..." textAlignment="CENTER" GridPane.columnIndex="1" />
         </children>
      </GridPane>
   </bottom>
   <center>
      <WebView prefHeight="200.0" prefWidth="200.0" BorderPane.alignment="CENTER" />
   </center>
</BorderPane>

Controller.java:

package Weert;

import javafx.fxml.FXML;
import javafx.fxml.Initializable;

import javafx.event.ActionEvent;
import java.net.URL;
import java.util.ResourceBundle;

public class Controller implements Initializable
{
    @Override
    public void initialize(URL url, ResourceBundle resourceBundle)
    {
    }
    @FXML
    public void Dagrooster(ActionEvent event)
{
    System.out.println("lollolol");
    }
}

Error:

Exception in Application start method
Exception in thread "main" 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$2/381259350.run(Unknown Source)
at java.lang.Thread.run(Thread.java:745)
Caused by: javafx.fxml.LoadException: No controller specified.
/F:/foo/Weert.fxml:24

at javafx.fxml.FXMLLoader.constructLoadException(FXMLLoader.java:2601)
at javafx.fxml.FXMLLoader.access$100(FXMLLoader.java:104)
at javafx.fxml.FXMLLoader$Element.getControllerMethodHandle(FXMLLoader.java:553)
at javafx.fxml.FXMLLoader$Element.processEventHandlerAttributes(FXMLLoader.java:595)
at javafx.fxml.FXMLLoader$ValueElement.processEndElement(FXMLLoader.java:766)
at javafx.fxml.FXMLLoader.processEndElement(FXMLLoader.java:2827)
at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:2536)
at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:2445)
at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3218)
at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3179)
at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3152)
at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3128)
at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3108)
at javafx.fxml.FXMLLoader.load(FXMLLoader.java:3101)
at Weert.Main.start(Main.java:13)
at com.sun.javafx.application.LauncherImpl.lambda$launchApplication1$159(LauncherImpl.java:863)
at com.sun.javafx.application.LauncherImpl$$Lambda$52/826215799.run(Unknown Source)
at com.sun.javafx.application.PlatformImpl.lambda$runAndWait$172(PlatformImpl.java:326)
at com.sun.javafx.application.PlatformImpl$$Lambda$48/1784984253.run(Unknown Source)
at com.sun.javafx.application.PlatformImpl.lambda$null$170(PlatformImpl.java:295)
at com.sun.javafx.application.PlatformImpl$$Lambda$50/965429099.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at com.sun.javafx.application.PlatformImpl.lambda$runLater$171(PlatformImpl.java:294)
at com.sun.javafx.application.PlatformImpl$$Lambda$49/1334999168.run(Unknown Source)
at com.sun.glass.ui.InvokeLaterDispatcher$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$38/184875764.run(Unknown Source)
... 1 more

Answer 1

The error says it, the FXML is missing the fx:controller declaration. Add the controller declaration to BorderPane declaration as shown :

...
<BorderPane maxHeight="1.7976931348623157E308" 
      maxWidth="1.7976931348623157E308" prefHeight="400.0" 
       prefWidth="600.0" xmlns="http://javafx.com/javafx/8"
         xmlns:fx="http://javafx.com/fxml/1" 
                          fx:controller="Weert.Controller">
...

To know how to set controller class via SceneBuilder, you can have a look at this question.

Answer 2

As the error implies, problem is in "fxml", in which it is referring to class which do not exist. To solve this search an attribute called "fx:controller" and assign it qualified class name . For an instance "fx:controller="packagename.className".