Two plus One Methods
The interface defines a protocol with 3 methods; only two of
them: jspInit() and jspDestroy() are part of this interface as
the signature of the third method: _jspService() depends on
the specific protocol used and cannot be expressed in a generic
way in Java.
A class implementing this interface is responsible for invoking
the above methods at the appropriate time based on the
corresponding Servlet-based method invocations.
The jspInit() and jspDestroy() methods can be defined by a JSP
author, but the _jspService() method is defined automatically
by the JSP processor based on the contents of the JSP page.
The _jspService()method corresponds to the body of the JSP page. This
method is defined automatically by the JSP container and should never
be defined by the JSP page author.
If a superclass is specified using the extends attribute, that
superclass may choose to perform some actions in its service() method
before or after calling the _jspService() method. See using the extends
attribute in the JSP_Engine chapter of the JSP specification.
The specific signature depends on the protocol supported by the JSP page.
public void _jspService(ServletRequestSubtype request,
throws ServletException, IOException;