Bonjour
je débute en Java
j'ai créé un composant dont voici le contenu du fichier fxml

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<?xml version="1.0" encoding="UTF-8"?>
 
<?import java.lang.*?>
<?import javafx.scene.control.*?>
<?import javafx.scene.layout.*?>
 
<fx:root minHeight="-Infinity" minWidth="-Infinity" prefHeight="200.0" prefWidth="132.0" type="javafx.scene.layout.AnchorPane" xmlns="http://javafx.com/javafx/8" xmlns:fx="http://javafx.com/fxml/1">
    <children>
        <Button id="btnCustom" fx:id="btnDea" alignment="CENTER" contentDisplay="CENTER" maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity" mnemonicParsing="false" onAction="#doSomething" prefHeight="100.0" prefWidth="100.0" text="DeaButton" textAlignment="CENTER" AnchorPane.leftAnchor="16.0" AnchorPane.rightAnchor="16.0" AnchorPane.topAnchor="16.0" />
        <Label id="lblCustom" fx:id="lblDea" alignment="CENTER" contentDisplay="CENTER" minHeight="-Infinity" minWidth="-Infinity" prefHeight="50.0" prefWidth="100.0" text="Label" textAlignment="CENTER" wrapText="true" AnchorPane.leftAnchor="16.0" AnchorPane.rightAnchor="16.0" AnchorPane.topAnchor="132.0" />
    </children>
</fx:root>
et le controller
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package sample.gui.custom;
 
import javafx.beans.property.SimpleStringProperty;
import javafx.beans.property.StringProperty;
import javafx.event.ActionEvent;
import javafx.fxml.FXML;
import javafx.fxml.FXMLLoader;
import javafx.scene.control.Button;
import javafx.scene.control.Label;
import javafx.scene.layout.AnchorPane;
 
import java.io.IOException;
import java.util.logging.Level;
import java.util.logging.Logger;
 
 
public class CustomButton extends AnchorPane {
 
    private static final Logger logger = Logger.getLogger(CustomButton.class.getName());
    public StringProperty stringProperty = new SimpleStringProperty();
 
    @FXML
    private  Label lblCustom;
    @FXML
    private  Button btnCustom;
 
 
    public CustomButton() {
        //super();
 
        FXMLLoader fxmlLoader = new FXMLLoader(getClass().getResource("CustomButton.fxml"));
        fxmlLoader.setController(this);
        fxmlLoader.setRoot(this);
 
        this.setWidth(132);
        this.setHeight(200);
 
 
        try {
            fxmlLoader.load();
        } catch (IOException ex) {
            Logger.getLogger(CustomButton.class.getName()).log(Level.SEVERE, null, ex);
        }
    }
 
 
    public String getLblCustomtext() {
        return lblCustom.getText();
    }
 
    public void setLblCustomText(String value) {
        lblCustom.setText(value);;
    }
 
    @FXML
    protected void doSomething() {
        System.out.println("The button was clicked!");
        System.out.println(getLblCustomtext());
    }
}
je l'utilise grâce à une application de test avec le code suivant
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package sample;
 
import javafx.application.Application;
import javafx.application.Preloader;
import javafx.beans.property.BooleanProperty;
import javafx.beans.property.SimpleBooleanProperty;
import javafx.concurrent.Task;
import javafx.scene.Scene;
import javafx.scene.layout.StackPane;
import javafx.stage.Stage;
 
import sample.gui.custom.CustomButton;
 
 
 
public class TestApp extends Application {
    Stage stage;
 
    public static void main(String[] args) {
        launch(args);
    }
 
 
 
    @Override
    public void start(final Stage stage) throws Exception {
        CustomButton customButton = new CustomButton();
        StackPane root = new StackPane();
        root.getChildren().add(customButton);
        stage.setScene(new Scene(root, 400, 400));
        stage.show();
    }
}
l'apllication fonctionne correctement mais quand jze clique sur le bouton, je reçois une execption

The button was clicked!
Exception in thread "JavaFX Application Thread" java.lang.RuntimeException: java.lang.reflect.InvocationTargetException
at javafx.fxml.FXMLLoader$MethodHandler.invoke(FXMLLoader.java:1770)
at javafx.fxml.FXMLLoader$ControllerMethodEventHandler.handle(FXMLLoader.java:1653)
at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:86)
at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:238)
at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:191)
at com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:59)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:58)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:74)
at com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:49)
at javafx.event.Event.fireEvent(Event.java:198)
at javafx.scene.Node.fireEvent(Node.java:8390)
at javafx.scene.control.Button.fire(Button.java:185)
at com.sun.javafx.scene.control.behavior.ButtonBehavior.mouseReleased(ButtonBehavior.java:182)
at com.sun.javafx.scene.control.skin.BehaviorSkinBase$1.handle(BehaviorSkinBase.java:96)
at com.sun.javafx.scene.control.skin.BehaviorSkinBase$1.handle(BehaviorSkinBase.java:89)
at com.sun.javafx.event.CompositeEventHandler$NormalEventHandlerRecord.handleBubblingEvent(CompositeEventHandler.java:218)
at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:80)
at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:238)
at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:191)
at com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:59)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:58)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:74)
at com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:54)
at javafx.event.Event.fireEvent(Event.java:198)
at javafx.scene.Scene$MouseHandler.process(Scene.java:3758)
at javafx.scene.Scene$MouseHandler.access$1500(Scene.java:3486)
at javafx.scene.Scene.impl_processMouseEvent(Scene.java:1762)
at javafx.scene.Scene$ScenePeerListener.mouseEvent(Scene.java:2495)
at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:350)
at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:275)
at java.security.AccessController.doPrivileged(Native Method)
at com.sun.javafx.tk.quantum.GlassViewEventHandler.lambda$handleMouseEvent$350(GlassViewEventHandler.java:385)
at com.sun.javafx.tk.quantum.GlassViewEventHandler$$Lambda$112/2091436502.get(Unknown Source)
at com.sun.javafx.tk.quantum.QuantumToolkit.runWithoutRenderLock(QuantumToolkit.java:404)
at com.sun.javafx.tk.quantum.GlassViewEventHandler.handleMouseEvent(GlassViewEventHandler.java:384)
at com.sun.glass.ui.View.handleMouseEvent(View.java:555)
at com.sun.glass.ui.View.notifyMouse(View.java:927)
at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
at com.sun.glass.ui.win.WinApplication.lambda$null$145(WinApplication.java:101)
at com.sun.glass.ui.win.WinApplication$$Lambda$38/774324403.run(Unknown Source)
at java.lang.Thread.run(Thread.java:745)
Caused by: java.lang.reflect.InvocationTargetException
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:497)
at sun.reflect.misc.Trampoline.invoke(MethodUtil.java:71)
at sun.reflect.GeneratedMethodAccessor1.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:497)
at sun.reflect.misc.MethodUtil.invoke(MethodUtil.java:275)
at javafx.fxml.FXMLLoader$MethodHandler.invoke(FXMLLoader.java:1767)
... 50 more
Caused by: java.lang.NullPointerException
at sample.gui.custom.CustomButton.getLblCustomtext(CustomButton.java:50)
at sample.gui.custom.CustomButton.doSomething(CustomButton.java:60)
... 60 more
lblCustom dans le controler est toujours nul

si j'essaie de definir le texte du label à la création par
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customButton.setLblCustomText("Mon texte");
j'ai le même problème.
l'erreur est probablement évidente.
j'ai fouillé sur le net mais je n'arrive pas à trouver d'info.

merci pour votre aide
cordialement