JavaFX Exception in thread "main" java.lang.NoClassDefFoundError: javafx/application/Application

I'm getting this error

Exception in thread "main" java.lang.NoClassDefFoundError: javafx/application/Ap
plication
        at java.lang.ClassLoader.defineClass1(Native Method)
        at java.lang.ClassLoader.defineClass(Unknown Source)
        at java.security.SecureClassLoader.defineClass(Unknown Source)
        at java.net.URLClassLoader.defineClass(Unknown Source)
        at java.net.URLClassLoader.access$100(Unknown Source)
        at java.net.URLClassLoader$1.run(Unknown Source)
        at java.net.URLClassLoader$1.run(Unknown Source)
        at java.security.AccessController.doPrivileged(Native Method)
        at java.net.URLClassLoader.findClass(Unknown Source)
        at java.lang.ClassLoader.loadClass(Unknown Source)
        at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
        at java.lang.ClassLoader.loadClass(Unknown Source)
        at sun.launcher.LauncherHelper.checkAndLoadMain(Unknown Source)
Caused by: java.lang.ClassNotFoundException: javafx.application.Application
        at java.net.URLClassLoader$1.run(Unknown Source)
        at java.net.URLClassLoader$1.run(Unknown Source)
        at java.security.AccessController.doPrivileged(Native Method)
        at java.net.URLClassLoader.findClass(Unknown Source)
        at java.lang.ClassLoader.loadClass(Unknown Source)
        at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
        at java.lang.ClassLoader.loadClass(Unknown Source)
        ... 13 more

When trying to run my class file, this is the source

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

import java.util.concurrent.Executor;

public class TestApplication extends Application{

    @Override
    public void start(Stage stage) throws Exception {
        new TestApplication();
    }

    public TestApplication() {
        try{
            final Parent root = FXMLLoader.load(Executor.class.getResource("test.fxml"));
            final Stage stage = new Stage(){{
                setScene(new Scene(root, 300, 250));
                setTitle("Test");
                setResizable(false);
                show();
            }};
        }catch(Exception e){
            e.printStackTrace();
        }
    }
}

The fxml file contains a simple gui.

I've worked on this very same issue for the past few hours. Even though I haven't seen it written explicitly, it appears that you MUST use one of the JavaFX packaging tools, which is either an Ant task or the javafxpackager executable. (See http://docs.oracle.com/javafx/2/deployment/packaging.htm, section 5.3.1). The NetBeans IDE uses Ant to package the code. (I'm using IntelliJ)

When you use one of those packaging methods, in addition to all of your application's code and resources, it also adds the following to your output JAR file:

/com/javafx/main/Main$1.class
/com/javafx/main/Main$2.class
/com/javafx/main/Main.class
/com/javafx/main/NoJavaFXFallback.class

With these in place, you can run the app from the command line:

java -jar outjar.jar

and all works fine. If I remove the extra com.javafx.main files, the app does not run.

To double-check this, I looked at all four JAR files in the JavaFX samples (BrickBreaker, Ensemble, FXML-LoginDemo, and SwingInterop). They all have the "extra" files, too.

For my small test app, I used this command line to build an "executable" JAR file:

javafxpackager -createjar -appclass sample.Main -outfile outjar -v -nocss2bin -srcdir C:\workspaces\garoup1\out\production\javafx1

Hope this helps!

I had the same problem and below steps helped me to solve it,

Adding the vm arguments while running the application,

--module-path  /home/user/Java-libraries/openjfx-11.0.2_linux-x64_bin-sdk/javafx-sdk-11.0.2/lib/ --add-modules javafx.controls,javafx.fxml

Note:

• The --module-path will contain the jars of Java fx
• I used open-jdk 13

Configure this in your eclipse (If you are using so) or you can just compile and run like,

Compile

javac --module-path /path/to/java-fx-libs/ --add-modules javafx.controls,javafx.fxml *.java

Run

java --module-path /path/to/java-fx-libs/ --add-modules javafx.controls,javafx.fxml MyMainClass

I know it may not be the "proper" way of launching an javafx application but i have struggled with this problem for some time and came up with a workaround that does not require to use any external packaging applications, force you to use ant or maven plugin (which conflicts with the shade plugin) etc...

The solution uses Utils4j to load jfxrt dynamically at runtime. You cannot load it in a class extending javafx.application.Application, do it in a separate class and name it for example: Launcher

import org.fuin.utils4j.Utils4J

public class Launcher {

    public static void main(String[] args) {
        Utils4J.addToClasspath("file:///"+System.getProperty("java.home")+ File.separator+"lib"+File.separator+"jfxrt.jar");

// CODE TO RUN YOUR CLASS THAT EXTENDS javafx.application.Application goes here.

    }
}

you can include Utils4j with your project (if using maven):

    <dependency>
        <groupId>org.fuin</groupId>
        <artifactId>utils4j</artifactId>
        <version>0.7.0</version>
    </dependency>