无法使用htmlUnit获取基于JavaScript的html输出

使用firebug，我可以在网页上看到以下错误语句

<div id="pageErrors" class=" xPrintAdaptX xPrintAdaptY">
<div class="xTplContent xPrintAdaptX xPrintAdaptY" _template="modules.cmtng.templates.panels.Messages" atdelegate="d104">
    <div class="errors-wrapper">
        <ul id="errorList" class="errors">
            <li class="error last">
                <em>4649</em>
                - This trip cannot be found. It may have been cancelled. (4649)
            </li>
        </ul>
    </div>
</div>
</div>

String strURL = "https://www.checkmytrip.com/cmt/apf/cmtng/index?LANGUAGE=GB&SITE=NCMTNCMT#pnr/retrieve/53w3kb/brown" ;
WebClient webClient = new WebClient(BrowserVersion.FIREFOX_31);
webClient.getOptions().setJavaScriptEnabled(true);
webClient.getOptions().setRedirectEnabled(true);
webClient.getCookieManager().setCookiesEnabled(true);
webClient.getOptions().setThrowExceptionOnScriptError(false);
webClient.setAjaxController(new NicelyResynchronizingAjaxController());
webClient.waitForBackgroundJavaScriptStartingBefore(30 * 1000);
HtmlPage myPage = (HtmlPage) webClient.getPage(strURL);
webClient.waitForBackgroundJavaScript(30 * 1000);
String cancelMessage ="This trip cannot be found. It may have been cancelled." ;
String content = "";

    while (true) {
        content = myPage.asText();
        System.out.println("***********************  wait  ************************************************");
        System.out.println(myPage.asXml());
        System.out.println("*************************************************************************");
        if (content.contains(cancelMessage)) {
            break;
        }
        try {
            synchronized (myPage) {
                myPage.wait(500);
            } // end synch
        } catch (InterruptedException ex) {
                ex.printStackTrace();
        }// end try-catch
    } // end while
    if (content.contains(cancelMessage)) {
        JOptionPane.showMessageDialog(null, " Error Statement Found. ");
    }