What is Servlet ?

A servlet is a Java programming language class that is used to extend the capa-
bilities of servers that host applications access via a request-response program-
ming model. Although servlets can respond to any type of request, they are
commonly used to extend the applications hosted by web servers. For such appli-
cations, Java Servlet technology defines HTTP-specific servlet classes.
The javax.servlet and javax.servlet.http packages provide interfaces and
classes for writing servlets. All servlets must implement the Servlet interface,