 concrete subclasses within the implementation that map concepts in the Facelet VDL page to Jakarta Server
 Faces Java API calls the appropriate instances. For example, the &#8220;<code>validator</code>&#8221; attribute on an
 input component is specified to point to a <code>MethodExpression</code> that references a method that performs the
 validation. There is a concrete subclass of <code>Metadata</code> to perform this action when that attribute appears
 in a Facelet VDL page.
 </p></div>
<dl class="note