JavaServer Pages, 3rd Edition

Servlets, Filters, and Listeners

A servlet is a Java class that extends a server with functionality for processing a request and producing a response. It’s implemented using the classes and interfaces defined by the Servlet API. The API consists of two packages: the javax.servlet package contains classes and interfaces that are protocol-independent, while the javax.servlet.http package provides HTTP-specific extensions and utility classes.

What makes a servlet a servlet is that the class implements an interface named javax.servlet.Servlet , either directly or by extending one of the support classes. This interface defines the methods used by the web container to manage and interact with the servlet. A servlet for processing HTTP requests typically extends the javax.servlet.http.HttpServlet class. This class implements the Servlet interface and provides additional methods suitable for HTTP processing.