code: protected void evaluateAttributes(E element, ELContext elContext) throws JspTagException, IOException {
  		String idStr = nullIfEmpty(resolveValue(id, String.class, elContext));
  		if(idStr != null) element.setId(idStr);
  	}
docs: Resolves all attributes, setting into the created element as appropriate,
  This is only called for captureLevel >= META.
  Attributes are resolved before the element is added to any parent node.
  Typically, deferred expressions will be evaluated here.
  Overriding methods must call this implementation.