More Servlets and JavaServer Pages™

2.6. The Servlet Equivalent of the Standard CGI Variables

If you come to servlets with a background in traditional Common Gateway Interface (CGI) programming, you are probably used to the idea of “CGI variables.” These are a somewhat eclectic collection of information about the current request. Some are based on the HTTP request line and headers (e.g., form data), others are derived from the socket itself (e.g., the name and IP address of the requesting host), and still others are taken from server installation parameters (e.g., the mapping of URLs to actual paths).

Although it probably makes more sense to think of different sources of data (request data, server information, etc.) as distinct, experienced CGI programmers may find it useful to ...