observable.java

public class XmlElementAttributeObservableValue extends AbstractObservableValue{
 	Element element;
 	String propertyName;
 	public XmlElementAttributeObservableValue( Element element, final String propertyName) {
 		this.element = element;
 		this.propertyName = propertyName;
 		addListner(this.element, this.propertyName);
 	}

		private void addListner(final Element element, final String propertyName) {
 		ElementImpl elementImpl = (ElementImpl) element;
 		elementImpl.addEventListener("DOMAttrModified", new EventListener(){

				public void handleEvent(Event evt) {
 				final MutationEvent mutEvent = (MutationEvent) evt;
 				 if( mutEvent.getAttrName().equals(propertyName)){
 					 fireValueChange(new ValueDiff(){

							@Override
 						public Object getNewValue() {
 							return mutEvent.getNewValue();
 						}
 						@Override
 						public Object getOldValue() {
 							return mutEvent.getPrevValue();
 						}

						 });
 				 }
 			}

			}, false);
 	}

		public Object getValueType() {
 		return String.class;
 	}
 	public boolean isStale() {
 		return false;
 	}
 	@Override
 	protected Object doGetValue() {
 		return element.getAttribute(propertyName);
 	}
 	@Override
 	protected void doSetValue(Object value) {
 		element.setAttribute(propertyName, (String) value);
 	}
 }