How servlet's init method is overridden ?

Here is a sample code to override servlet's init method.
public class BookDBServlet ... {
        private BookstoreDB books;
        public void init(ServletConfig config) throws ServletException {
            // Store the ServletConfig object and log the initialization
            // Load the database to prepare for requests
            books = new BookstoreDB();
    }I dont get why super.init(config); is called.
Comment says +// Store the ServletConfig object and log the initialization+
what does "Store" mean here ? Where it is stored ?
how it is logged ( log4j / commons -logging ? ) and where (which file) it is logged ?
Can we remove this line without any damage ?

There are several calls you can make to the servlet object which are simply delegated to the ServletConfig object, most notably getServletContext(). The default action of the init(SerletConfig config) method is to store the config in a field which is defined in GenericServlet, so that these calls can work. If you don't do this then calling getServletContext() at some later time will give you a NullPointerException.
I think the reference to logging is that, if you use the built in servlet logging system, rather than log4j or java.util.loging then this depends on a valid servlet context, which in turn, depends on a valid servlet config reference.

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