@Override public void onComponentTag(Component component, ComponentTag tag) { Object node = component.getDefaultModelObject(); String klass = getItemClass(node); if (!Strings.isEmpty(klass)) { CharSequence oldClass = tag.getAttribute("class"); if (Strings.isEmpty(oldClass)) { tag.put("class", klass); } else { tag.put("class", oldClass + " " + klass); } } } });