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Introduction to Java Servlets

A Bit of History

Before the Servlet API was introduced, web designers could add interactive functionality to their sites by using CGI (Common Gateway Interface) scripts.

In the beginning, Web Servers were made to just serve basic text content and images. However, in order to provide an interactive environment, the web server had to be extended to allow programs or scripts to be executed. This interface was standardized as CGI.

The browser would load an HTML page consisting of some form elements such as text boxes or check boxes. Then, the user would fill in the form and submit it to the web server. The Web Server would take the form data and submit the data to the CGI program. When the CGI program runs, it outputs the relevant HTML or other data back to the Web Server which acts as a middle-man and sends the data back to the browser. The diagram below illustrates the life cycle of a browser getting results from a CGI program.

This brings us to Servlets. If CGI programs work so well, why use Servlets?

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Gunther Birznieks contributes to JavaBoutique's Web/Networking column. Gunther currently works for Barclays Capital in London, one of the leading global investment banks in Europe and has previously worked as a senior computer scientist in the Human Genome Project. Gunther is also known for writing several books on Web Programming (Perl, CGI, Java) as well as for co-creating Extropia with Selena Sol. Extropia is one of the best known public domain web programming archives Email: gunther@extropia.com.

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