javafx parameters in command prompt gives null values

Question

Goodevening everyone,

This might be a silly question but I seem to struggle finding an answer to it. I've created a simple JavaFX8 program that should be able to read command line arguments.

Let me illustrate:

public void start(Stage stage) throws Exception {       
    Map parameters = getParameters().getNamed();

    System.out.println("parameter is " + parameters.get("myKey"));

    ...
}

When I define a parameter named myKey in NetBeans with value abc,

it results in the following output when I run my application from the IDE:

parameter is abc

However, if I run it from the command prompt as following:

java -jar MyApp.jar myKey=abc

it returns value null, which means the parameters isn't forwarded to the JavaFX application:

parameter is null

Why is this? It's the first time I'm working with parameters so apologies if the answer is really easy.

Answer 1

The key is to use the following syntax when calling from command-line:

java -jar JavaHelp.jar --p1=hello --p2=world

getNamed only returns something if parameter is annotated with -- (I think this equals 'NAMED')

Try it with this program and you can see:

public class Main extends Application {

    @Override
    public void init() throws Exception {
        super.init();
        System.out.println(getParameters().getRaw().toString());
        getParameters().getNamed().forEach((name, string) -> {
            System.out.println("Parameter[" + name + "]=" + string);
        });
    }

    @Override
    public void start(Stage primaryStage) throws Exception {
        primaryStage.setTitle("Hello World");
        primaryStage.setScene(new Scene(new Pane() {{
            getChildren().add(new Button("B"));
        }}));
        primaryStage.show();

    }


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

This will print:

Parameter[p1]=hello
Parameter[p2]=world

Answer 2

You need -- before each argument. So the command you need is:

java -jar MyApp.jar --myKey=abc