https://medium.com/@tsepomaleka/integrating-spring-boot-with-java-server-faces-using-joinfaces-297e64f6a28f

I was introduced to Spring quite later in my software engineering career. I began my coding days in the workplace with Java Server Faces, as many would know it with its acronym, JSF. JSF is a powerful MVC (model-view-controller) Java standard technology used mainly for building component-based and event-driven web interfaces using the simple concept of beans and XHTML pages.

A bean in JSF can both be a controller and a model (or anything, actually). There is no pre-defined standard in the framework to distinguish between what a model bean is and a controller bean (unlike Spring, for example). In fact, JSF has left that decision and flexibility to the architects and developers. Views are well defined as XHTML pages. XHTML has the same extensive expressions as HTML but strictly conforms to the XML syntax. XHTML pages allow for the creation of new components that can be reused across your project.