calling a JavaScript function with HTMLUnit

I'm trying to call the function `showPage('3');` of this page, for use the page source code after. I tried to do with `htmlUnit` like so: ``` WebClient webClient = new WebClient(); webClient.waitForBackgroundJavaScriptStartingBefore(10000); HtmlPage page = webClient.getPage("http://www.visittrentino.it/it/cosa_fare/eventi/risultati?minEventDate=09012014&maxEventDate=31012014&tp=searchForm.thismonth&ltp=gennaio"); String javaScriptCode = "showPage('3');"; ScriptResult result = page.executeJavaScript(javaScriptCode); result.getJavaScriptResult(); System.out.println("result: "+ result); ``` But it's not working. It prints out: result: net.sourceforge.htmlunit.corejs.javascript.Undefined@a303147 and other 10000 warnings. What am I doing wrong? I need to change the page of this site for do some crawling on the source code. Is there another way (and maybe more easier) for calling jsp-function from Java code and then navigate in the source of the page? Thank you for any help, have a nice day.