检查JavaFX WebEngine中存在的JS函数

Question

我需要从javafx Webengine中的文件myFunctions.js执行脚本，并使用resttemplate将信息发送到服务器：

public void onDeviceStatusChanged(DeviceStatusEvent deviceStatusEvent) {

        String uri = defaultPage + "my/" + "devices/status";

        if (deviceStatusEvent.getDevStat().getDev() == 0) {
            webEngine.executeScript("billAcceptorStatus(" + deviceStatusEvent.getDevStat().getStatus() + ")");
        }
        if (deviceStatusEvent.getDevStat().getDev() == 1) {
            webEngine.executeScript("posPrinterStatus(" + deviceStatusEvent.getDevStat().getStatus() + ")");
        }
        if (deviceStatusEvent.getDevStat().getDev() == 2) {
            webEngine.executeScript("cardReaderStatus(" + deviceStatusEvent.getDevStat().getStatus() + ")");
        }
        if (deviceStatusEvent.getDevStat().getDev() == 4) {
            webEngine.executeScript("pinPadStatus(" + deviceStatusEvent.getDevStat().getStatus() + ")");
        }
        try {
            if (deviceStatusEvent.getDevStat().getDev() == 0) {
                if (deviceStatusEvent.getDevStat().getStatus() == 2) {
                    HttpEntity request = new HttpEntity<>(defaultHeaders.getMap());
                    String string = restTemplate.postForObject(defaultPage + "/my/" + "devices/ink", request, String.class);
               }
            }

            HttpEntity<SimpleDevStat> request = new HttpEntity<>(deviceStatusEvent.getDevStat(), defaultHeaders.getMap());
            restTemplate.postForLocation(uri, request);
            log.debug("Posted : " + deviceStatusEvent.getDevStat());
            webEngine.executeScript("networkStatus(true)");
        } catch (Exception e) {
            webEngine.executeScript("networkStatus(false)");
            e.printStackTrace();
        }
    }

如果未将myFunctions.js加载到webengine，则webengine.executeScript（）无效并且代码会停止此行。我需要检查webengine中是否存在myFunctions.js。如何检查webengine中的js文件？