code: private void makeStaticallyInitializedPropertiesReactive(JsObject object, String className) {
      Map<String, Object> cache = classesPropertyCaches.get(className);
      if (cache == null) {
        cache = initClassPropertiesCache(object, className);
      }
  
      JsPropertyMap<Object> javaObjectPropertyMap = ((JsPropertyMap<Object>) object);
      cache.forEach((key, value) -> {
        if (!object.hasOwnProperty(key)) {
          javaObjectPropertyMap.set(key, value);
        }
      });
    }
docs: Due to GWT optimizations, properties on java object defined like this are not observable in
  Vue.js when not running in dev mode: <br>
  private String myText = "Default text"; private int myInt = 0; <br>
  This is because GWT define the default value on the prototype and don't define it on the
  object. Therefore Vue.js don't see those properties when initializing it's observer. To fix the
  issue, we manually look for those properties and set them explicitly on the object.
  
  @param object The Java object to observe
  @param className The Java class name to observe