Is there a way to use a reference to an existing java class from javascript in Vaadin?

i currently have the problem, that i want to use a reference of an existing java class in javascript to be able to execute methods from Javascript of the Java Class to use Shepherd (Javascript Tool for guiding users through the web app). Im using Vaadin for Web deployment with java but Shepherd only works through Javascript.
I dont want to execute the JS from the Class with the methods, moreover i want to execute it from an other class, so it looks like this:

1. User clicks on a Button

> Button button = new Button(); button.addClickListener (c -> tourPageController.executeShepherd(UI.getCurrent().getInternals().getTitle());

2. Java Code to find active Page

> public static void executeShepherd(String appTitle) {switch(appTitle) {case "example": UI.getCurrent().getPage().executeJs("window.startTour($0)", <here i want to reference the existing class with the methods);

3. execute the Shepherd Tour four the explicit page, the user is on (For that, i need to hand over
   a reference of the class holding the methods to execute via javascript), its looks something like this in the header:

> window.startTour = (<classParameter>) => { ... }

4. Javascript is getting the parameter (the class)

5. From Javascript im going to use Shepherd, but there are references to Java Methods (these Methods are for the Vaadin Components, to open and close the respectively tabs i want to use in the tour). I use it like this:

    beforeShowPromise: function () {
    	return new Promise(function(resolve) {
    		classParameter.$server.<method()>;
            resolve();
    	});
    },
   

How can i do this?

What you can do is to set id to the component in Java

component.setId("component-x");

This will mean that the DOM element will be have the id attribute set.

So if you have some bookkeeping of the components in your Java code, you can pass the id as a parameter in that @ClientCallable call, and then search for the component matching that id in your Java code.

If this is about only one view specific component, you do not need anything else than storing reference to the component in a class field (not even the id). But if you indeed have more than one Accordion in your view, the idea is like this.

public class MyView extends Div {

    List<Accordion> accordions;

    public MyView() {
        Accordion accordion = new Accordion();
        accordion.setId("accordion-1");
        accordions.add(accordion);
        ...
    }

    @ClientCallable
    public openAccordion(String id, int index) {
        accordions.stream().filter(acc -> 
        acc.getId().equals(id)).findFirst().ifPresent(acc -> acc.open(null));
        accordion.open(index);
    }
}

For context, see: https://stackoverflow.com/questions/75457945/how-can-i-change-vaadin-components-in-java-through-javascript/75459882