@Override
 protected void setTarget(EObject target) {
   if (target.eResource() instanceof XtextResource) {
     super.setTarget(target);
   }
 }
 /** Only attach to XtextResources */
 @Override
 protected void setTarget(Resource target) {
   if (target instanceof XtextResource) {
     super.setTarget(target);
   }
 }