Best Practices for Using Component Facets
A facet consists of content in an area of a Visualforce component that provides contextual information about the data that is presented in the component. For example, <apex:dataTable> supports facets for the header, footer, and caption of a table, while <apex:column> only supports facets for the header and footer of the column. The <apex:facet> component allows you to override the default facet on a Visualforce component with your own content. Facets only allow a single child within the start and close tags.
Not all components support facets. Those that do are listed in the Standard Visualforce Component Reference.
When defining an <apex:facet>, it is always used as the child of another Visualforce component. The name attribute on the facet determines which area of the parent component is overridden.
The following markup shows how the <apex:dataTable> component can be modified with <apex:facet>:
For this page to display account data, the ID of a valid account record must be specified as a query parameter in the URL for the page. For example:
The page displays as follows:
Another component that can use a facet is <apex:actionStatus>. The <apex:actionStatus> component can be extended to display an indicator whenever a page is being refreshed. For example, you can define a progress wheel with the following markup:
The associated controller updates the counter:
The page displays as follows:
See Also