IntelliJ IDEA - Error: JavaFX runtime components are missing, and are required to run this application

Question

I'm running IntelliJ IDEA Ultimate 2018.2.5 with JDK 11.0.1 and JavaFX 11 from OpenJFX. I know it's a common error and I tried many of the proposed fixes but nothing works.

No matter which JavaFX project I try to run I get the error:

Error: JavaFX runtime components are missing, and are required to run this application

If I add the following to the VM options

 --module-path="C:\Program Files\Java\javafx-sdk-11\lib" --add-modules=javafx.controls

I get these errors:

Exception in Application start method
java.lang.reflect.InvocationTargetException
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.base/java.lang.reflect.Method.invoke(Method.java:566)
    at javafx.graphics/com.sun.javafx.application.LauncherImpl.launchApplicationWithArgs(LauncherImpl.java:464)
    at javafx.graphics/com.sun.javafx.application.LauncherImpl.launchApplication(LauncherImpl.java:363)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.base/java.lang.reflect.Method.invoke(Method.java:566)
    at java.base/sun.launcher.LauncherHelper$FXHelper.main(LauncherHelper.java:1051)
Caused by: java.lang.RuntimeException: Exception in Application start method
    at javafx.graphics/com.sun.javafx.application.LauncherImpl.launchApplication1(LauncherImpl.java:900)
    at javafx.graphics/com.sun.javafx.application.LauncherImpl.lambda$launchApplication$2(LauncherImpl.java:195)
    at java.base/java.lang.Thread.run(Thread.java:834)
Caused by: java.lang.IllegalAccessError: class com.sun.javafx.fxml.FXMLLoaderHelper (in unnamed module @0x5fce9dc5) cannot access class com.sun.javafx.util.Utils (in module javafx.graphics) because module javafx.graphics does not export com.sun.javafx.util to unnamed module @0x5fce9dc5
    at com.sun.javafx.fxml.FXMLLoaderHelper.<clinit>(FXMLLoaderHelper.java:38)
    at javafx.fxml.FXMLLoader.<clinit>(FXMLLoader.java:2056)
    at sample.Main.start(Main.java:13)
    at javafx.graphics/com.sun.javafx.application.LauncherImpl.lambda$launchApplication1$9(LauncherImpl.java:846)
    at javafx.graphics/com.sun.javafx.application.PlatformImpl.lambda$runAndWait$12(PlatformImpl.java:455)
    at javafx.graphics/com.sun.javafx.application.PlatformImpl.lambda$runLater$10(PlatformImpl.java:428)
    at java.base/java.security.AccessController.doPrivileged(Native Method)
    at javafx.graphics/com.sun.javafx.application.PlatformImpl.lambda$runLater$11(PlatformImpl.java:427)
    at javafx.graphics/com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:96)
    at javafx.graphics/com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
    at javafx.graphics/com.sun.glass.ui.win.WinApplication.lambda$runLoop$3(WinApplication.java:174)
    ... 1 more
Exception running application sample.Main

I tried reinstalling without any luck. I have also tried to change getClass().getResource(...) to getClass().getClassLoader().getResource(...) or to something like Parent root = FXMLLoader.load(getClass().getResource("/sample.fxml")); but still doesn't work.

Solution

There are similar questions like this or this other one.

Before JavaFX 11, whenever you were calling something JavaFX related, you had all the javafx modules available within the SDK.

But now you have to include the modules/dependencies you need.

Your error says that you are using FXML but it can't be resolved, but you have just added the javafx.controls module:

--add-modules=javafx.controls

As you can see in the JavaDoc the javafx.controls module depends on javafx.graphics and java.base, but none of those modules includes the FXML classes.

If you need FXML classes like the FXMLLoader, you need to include javafx.fxml module:

 --module-path="C:\Program Files\Java\javafx-sdk-11\lib" \
    --add-modules=javafx.controls,javafx.fxml

The same will apply if you need media or webkit, those have their own modules.

Comments

[Alex H.]

If I am not completely wrong, you will have to replace the = with spaces

[José Pereda]

@AlexH. Both work, though space is preferred