A command button added to the toolbar of a Panel Collection component does not cause field validation in a form when pressed. While this appears confusing it works as designed.

Instead of a full page re-rendering, ADF Faces events and components can trigger partial page refresh, in which only portions of a page are refresh upon a request. In addition, some components - including the af:popup and af:subForm - represent event roots. Event roots don't propagated event notification outside of the component tag boundary, which means that the ADF Faces lifecycle only executed on components that are children of the event root component. The PanelCollection component is an event root and therefore only validates and refreshes data of its child components.