When FXMLLoader is invoked :
- on the attached file (DataSetUIv2.fxml)
- with FXMLLoader.impl_setStaticLoad(true)

it raises the NPE described below.
If the static load is disabled, then NPE does not appear.
So it seems that expression evaluation is not dealing correctly with static load.


Here is the NPE stack:

unknown path:137

at javafx.fxml.FXMLLoader.constructLoadException(FXMLLoader.java:2593)
at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:2571)
at javafx.fxml.FXMLLoader.load(FXMLLoader.java:2417)
at Oxebo.start(Oxebo.java:34)
at com.sun.javafx.application.LauncherImpl.lambda$launchApplication1$137(LauncherImpl.java:821)
at com.sun.javafx.application.LauncherImpl$$Lambda$51/105503094.run(Unknown Source)
at com.sun.javafx.application.PlatformImpl.lambda$runAndWait$149(PlatformImpl.java:319)
at com.sun.javafx.application.PlatformImpl$$Lambda$45/1851691492.run(Unknown Source)
at com.sun.javafx.application.PlatformImpl.lambda$null$147(PlatformImpl.java:288)
at com.sun.javafx.application.PlatformImpl$$Lambda$47/1567428247.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at com.sun.javafx.application.PlatformImpl.lambda$runLater$148(PlatformImpl.java:287)
at com.sun.javafx.application.PlatformImpl$$Lambda$46/815033865.run(Unknown Source)
at com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:95)
Caused by: java.lang.NullPointerException
at com.sun.javafx.fxml.expression.Expression.lambda$not$14(Expression.java:1476)
at com.sun.javafx.fxml.expression.Expression$$Lambda$101/1109741740.apply(Unknown Source)
at com.sun.javafx.fxml.expression.UnaryExpression.evaluate(UnaryExpression.java:49)
at com.sun.javafx.fxml.expression.ExpressionValue.getValue(ExpressionValue.java:192)
at com.sun.javafx.binding.ExpressionHelper.addListener(ExpressionHelper.java:54)
at javafx.beans.value.ObservableValueBase.addListener(ObservableValueBase.java:55)
at com.sun.javafx.fxml.expression.ExpressionValue.addListener(ExpressionValue.java:201)
at javafx.beans.binding.BooleanBinding.bind(BooleanBinding.java:107)
at javafx.beans.property.BooleanPropertyBase$1.<init>(BooleanPropertyBase.java:167)
at javafx.beans.property.BooleanPropertyBase.bind(BooleanPropertyBase.java:164)
at javafx.fxml.FXMLLoader$Element.processPropertyAttribute(FXMLLoader.java:314)
at javafx.fxml.FXMLLoader$Element.processInstancePropertyAttributes(FXMLLoader.java:231)
at javafx.fxml.FXMLLoader$ValueElement.processEndElement(FXMLLoader.java:761)
at javafx.fxml.FXMLLoader.processEndElement(FXMLLoader.java:2815)
at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:2524)
... 12 more



Here is a sample java class which exhibits the loading issue:

import java.io.IOException;
import java.io.InputStream;
import java.net.URL;

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


public class Oxebo extends Application {

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

/*
* Application
*/

@Override
public void start(Stage primaryStage) throws Exception {
Object root;
final URL fxmlURL = getClass().getResource("DataSetUiV2.fxml");
assert fxmlURL != null;
try (InputStream is = fxmlURL.openConnection().getInputStream()) {
FXMLLoader fxmlLoader = new FXMLLoader();
fxmlLoader.impl_setStaticLoad(true); // NOTE : static load
root = fxmlLoader.load(is);
assert root instanceof Parent;
} catch(IOException x) {
x.printStackTrace();
root = new Label("Load error");
}

primaryStage.setScene(new Scene((Parent)root));
primaryStage.sizeToScene();
primaryStage.show();
}

}