An application that wishes to use Facelets as a ViewHandler, they must specify the following in their faces-config.xml (@see com.sun.facelets.FaceletViewHandler).

<application>
  <view-handler>com.sun.facelets.FaceletViewHandler</view-handler>
</application>

Below is sample code for using Facelets at the API level with JavaServer Faces.

// get the view to render
FacesContext context = FacesContext.getCurrentInstance();
UIViewRoot viewToRender = context.getViewRoot();

// grab our FaceletFactory and create a Facelet
FaceletFactory factory = FaceletFactory.getInstance();
Facelet f = factory.getFacelet(viewToRender.getViewId());

// populate UIViewRoot
f.apply(context, viewToRender);