JSF 2 Internals - Entry of FacesServlet is optional

In JEE 6, major milestone achieved was reduction of configuration files e.g. in servlet based web application, no need to mention web.xml and application assumes default configuration settings. Same thing was also achieved in JSF 2. Now there is no need to mention FaceServlet or servlet mapping in web.xml. But question arises from where application picks these defaults? Answer is the "ServletContainerInitializer" interface which allows a library/runtime to be notified of a web application's startup phase and perform any required programmatic registration of servlets,filters, and listeners in response to it. Inside of "onStartup" implementation of JSF 2, all these defaults are set, Sample code is given below:

ServletRegistration reg =

servletContext.addServlet("FacesServlet",

"javax.faces.webapp.FacesServlet");

reg.addMapping("/faces/*", "*.jsf", "*.faces");

servletContext.setAttribute(RIConstants.FACES_INITIALIZER_MAPPINGS_ADDED, Boolean.TRUE);

JSF 2 class which implements this interface is "FacesInitializer" class and have been mentioned under jsf-ri.jar's META-INF/services folder.