☛ Java Servlet is server side technologies to extend the capability of web servers by providing support for dynamic response and data persistence.

☛ The javax.servlet and javax.servlet.http packages provide interfaces and classes for writing our own servlets.

☛ All servlets must implement the javax.servlet.Servlet interface, which defines servlet lifecycle methods. When implementing a generic service, we can extend the GenericServlet class provided with the Java Servlet API. The HttpServlet class provides methods, such as doGet() and doPost(), for handling HTTP-specific services.

☛ Most of the times, web applications are accessed using HTTP protocol and thats why we mostly extend HttpServlet class. Servlet API hierarchy is shown in below image.