How to create a JavaScript wrapper to be used with JavaFx WebView? Is JSNI an option?

I would like to use the JavaFx WebEngine in combination with the JavaScript library d3.js. I am already able to access the JavaScript library from within Java. That works using JSObjects as shown in [1]:

JSObject d3Object = (JSObject) webEngine.executeScript("d3");
JSObject chart= (JSObject) d3Object.call("select", ".chart");

As you see there is a general purpose method "call" and I have to pass the name of the JavaScript method that I want to invoke as a String. In order to use the JavaScript library d3.js more comfortably, I would like to have a Java wrapper for it, e.g.

JSObject d3Object = (JSObject) webEngine.executeScript("d3");
D3Wrapper d3 = new D3Wrapper(d3Object);
Selection chart = d3.select(".chart");

What is the recommended way to create such a JavaScript wrapper? I found out that there is already a wrapper for D3 that targets GWT applications. The main wrapper for the d3 object is located here:

https://github.com/gwtd3/gwt-d3/blob/master/gwt-d3-api/src/main/java/com/github/gwtd3/api/D3.java

It seems to be based on JSNI [2] and an example method definition is

public static final native Selection select(String selector)/*-{
    return $wnd.d3.select(selector);
}-*/;

The native code in the comment will be executed when calling the method from within Java. How can I take advantage of that existing wrapper code in my JavaFx desktop application? I never used GWT before and I do not want to run an extra web server. Do I really need to dive into GWT and run a full GWT application in the JavaFx WebEngine (if that is possible at all)? Or can I somehow only use the JSNI part of GWT together with the JavaFx WebEngine?

Here is an article on the debug mode for GWT and it seems to be quite complex: http://www.quora.com/How-does-GWT-live-javascript-debugging-in-Eclipse-work-and-how-could-it-be-applied-to-Clojure So I am afraid that there is no easy way to plug the WebEngine into such a work flow? Do I really need to manually rewrite each of the wrapping classes "already provides by gwt-d3"? If the native JavaScript code would be given by Annotations I could reuse the wrapper classes from gwt-d3 and process them by reflection.

If combining JSNI with JavaFx does not make any sense, what would be an elegant way to write an own wrapper for d3.js? Is there a Java library that helps me writing a JavaScript wrapper?