Generic and HttpServlet

In order to support HTTP session states, all servlet session data must be serializable.Moreover, servlets need to communicate over the network to Java objects(e.g. in Applet-Servlet communication),in such scenarios it becomes necessary to enable serialization of objects' states through implementation of Serializable interface.This is the way GenericServlet and HttpServlet classes have been designed by their designers to make them capable of serialization.

HttpServlet belongs to javax.servlet.http package.

HttpServlet extends GenericServlet . HttpServlet Provides an abstract class to be subclassed to create an HTTP servlet suitable for a Web site. A subclass of HttpServlet must override at least one method, usually one of these:

doGet, if the servlet supports HTTP GET requests
doPost, for HTTP POST requests
doPut, for HTTP PUT requests
doDelete, for HTTP DELETE requests

GenericServlet defines a generic, protocol-independent servlet. GenericServlet belongs to javax.servlet package . To write a generic servlet, you need only override the abstract service method.GenericServlet implements the Servlet and ServletConfig interfaces. GenericServlet may be directly extended by a servlet, although it?s more common to extend a protocol-specific subclass such as HttpServlet.

GenericServlet makes writing servlets easier. It provides simple versions of the lifecycle methods init and destroy and of the methods in the ServletConfig interface. GenericServlet also implements the log method, declared in the ServletContext interface.