code: public void apply(FaceletContext ctx, UIComponent parent) throws IOException, FacesException, FaceletException,
              ELException
      {
          AbstractFaceletContext actx = (AbstractFaceletContext) ctx;
          actx.extendClient(this);
          boolean found = false;
          try
          {
              found = actx.includeDefinition(parent, this.name);
          }
          finally
          {
              actx.popExtendedClient(this);
          }
          if (!found)
          {
              this.nextHandler.apply(ctx, parent);
          }
      }
docs: /*
  (non-Javadoc)
  
  @see javax.faces.view.facelets.FaceletHandler#apply(javax.faces.view.facelets.FaceletContext, javax.faces.component.UIComponent)