What is a jsp ?we can say jsp is a implement of HttpServlet.

JSP pages are textual components. They go through two phases: a translation
phase, and a request phase. Translation is done once per page. The request phase is
done once per request.
The JSP page is translated to create a servlet class, the JSP page
implementation class, that is instantiated at request time. The instantiated JSP
page object handles requests and creates responses.
JSP pages may be translated prior to their use, providing the web application,
with a servlet class that can serve as the textual representation of the JSP page.
The translation may also be done by the JSP container at deployment time, or
on-demand as the requests reach an untranslated JSP page.