Declarative components are reusable, composite user interface (UI) components that comprise other existing Application Development Framework (ADF) Faces components.

Consider an application that contains multiple JSF pages. On a particular page, a set of specific components is used in multiple parts of that page. In this scenario, if you make any changes to any of the components in the set, you typically must replicate the changes in multiple parts of the page. This approach makes it difficult to maintain the consistency of the structure and layout of the page. However, by defining a declarative component that comprises the given set of components, you can reuse that composite declarative component in multiple places or pages. Declarative components, thereby, save time and ensure integrity across pages because when you make any changes to the components, the JSF pages using them automatically get updated.

ADF task flows are reusable components that provide a modular and transactional method in specifying the control flow in an application. You can use a set of reusable task flows as an alternative to representing an application as a single large JSF page flow, thereby providing modularity. Each task flow contains a part of the entire navigational plan of the application. The nodes in a task flow are called activities. Apart from navigation, task flow activities can also call methods on managed beans or call another task flow without invoking any particular page. This facilitates reuse because business logic can be invoked independently of the page being displayed.