JFR uses dynamic proxies to get data, i.e. eventType.getAnnotation(MirrorEvent.class). This is convenient, but for known JDK classes we could get the annotation values directly without spinning up a proxy class, i.e.

String getMirrorClass() {
  for (var a : eventType.getAnnotationElements()) {
       if (a.getTypeId() == MIRROR_EVENT_TYPE_ID) {
         return (String)a.getValue("value");
       }
   }
   return null;
}