How to rewrite the DOM of a page on load within JavaFX WebView

I need to open a page in JavaFX WebView (i have done this part), then I need to rewrite the content of the dom before/as/after it loads, I have tried using the webEngine.executeScript() function to execute document.open(); document.write('my HTML content'); document.close(); , but have had little success, I know the javascript I have used works on chrome and firefox and was wondering if you outright cannot do this on WebView, and if so what the reason is, or if there is a way to do it