Error: JavaFX runtime components are missing - JavaFX 11 and OpenJDK 11 and Eclipse IDE

Your problem is not compiling the project, but running it. Since your main is defined in your Application-extension, running the project will require JavaFX in your module path on startup.

So either outsource your main into a class different from your Application or add the JavaFX modules with VM arguments:

--module-path="<javafx-root>\lib" --add-modules="javafx.base,javafx.controls,..."

See this for some more info.