Dynamic Web Pages

A dynamic document is produced by a program that can receive input from a user and modify the Web page based on that input. A typical mechanism for communication between a user's browser and a Web server is called the Common Gateway Interface (CGI). Altogether, the Common Gateway Interface (CGI) is a set of conventions, supported by software, that facilitate the writing of programs that generate World Wide Web documents. CGI programs can be written in almost any programming language; naturally, though, we'll use Java.

With CGI programming, the sequence of events for Web interaction has an extra step:

1. Within a Web browser, you type a URL.
2. Your browser sends a request to the server for that address.
3. The server finds the file on a disk drive.
4. The server retrieves the file from the disk and notes that the file identifies a program to run.
5. The server runs the program, which produces an HTML document.
   • The first line of the HTML document tells both the Web server and your browser that this will be a text-based html document, and thus clarifies how both the server and browser will communicate.
   • The rest of the HTML document contains formatting instructions and text for display.
6. The server sends the newly-produced HTML document back to your browser.
7. Your browser interprets the file and displays it on your screen.