Head First Servlets and JSP, 2nd Edition

You can’t use servlet init parameters until the servlet is initialized

You already saw that your servlet inherits getServletConfig(), so you can call that from any method in your servlet to get a reference to a ServletConfig. Once you have a ServletConfig reference, you can call getInitParameter(). But remember, you can’t call it from your constructor! That’s too early in the servlet’s life... it won’t have its full servletness until the Container calls init().

When the Container initializes a servlet, it makes a unique ServletConfig for the servlet.

The Container “reads” the servlet init parameters from the DD and gives them to the ServletConfig, then passes the ServletConfig to the servlet’s init() method.

There are no Dumb Questions

Q:	Q: Way back in the last chapter, you said it takes TWO things for the servlet to become a card-carrying, fez-wearing servlet. You mentioned both ServletConfig and something called ServletContext.
A:	A: OK, yes, we’ll look at the ServletContext in just a few pages. For now, we care only about ServletConfig, because that’s where you get your servlet init parameters.
Q:	Q: Wait a minute! In the last chapter you said that we could override the init() method, and nobody said a word about the ServletConfig argument!
A:	A: We didn’t mention that the init() method takes a ServletConfig because the one you override doesn’t take one. Your superclass includes two versions ...