In this chapter the Servlet API was introduced, and focus was placed specifically on Servlets. Servlets are the fundamental building block of server-side Java. A Servlet is highly scalable and easily outperforms traditional CGI by means of a simple three-phase life cycle: initialization, service, and destruction. Commonly, the term Servlets actually refers to HTTP Servlets used on the World Wide Web. The HttpServlet class is designed especially for this user and greatly simplifies server-side Java support for HTTP.
The basics of the Servlet API consist of objects that represent a client's request, HttpServletRequest, the server's response, HttpServletResponse, a session for connecting separate requests, HttpSession, and an entire Web Application, ServletContext. Each of these objects provides a complete set of methods for accessing and manipulating related information. These objects also introduce two new scopes for Servlet developers to use: request and application. Binding an object to these various scopes allows a Servlet developer to share an object between multiple Servlets and requests for extended periods of time. What was only briefly mentioned is that a third, commonly used scope, session, is also available. Session scope introduces several issues which merit a complete chapter's worth of information. Chapter 9 fully explains session scope and the issues relating to it.
Overall, this chapter is a reference to creating and using Servlets. Chapter 3 continues discussion of Servlets by introducing a complementary technology: JavaServer Pages.