code: protected Map getScratchMap() {
  		UIContext uic = UIContextHolder.getCurrent();
  		return uic == null ? null : uic.getScratchMap(this);
  	}
docs: <p>
  Retrieves a short-lived map which can be used to cache data during request processing. This map will be
  guaranteed to be cleared at the end of processing a request, but may also be cleared during request processing.
  Do not rely on the contents of this map to exist at any time.
  </p>
  <p>
  This method will return <code>null</code> if called outside of request processing.
  </p>
  
  @return a map which can be used to temporarily cache data, or null