newbie question

Hi:
following is from sample code:
<html>
<head>
<BASE HREF="<%= request.getScheme() %>://<%= request.getServerName() %>:<%= request.getServerPort() %><%= request.getContextPath() %>/">
</head>
<body>
</body>
</html>
request is a interface, how could it be used without any inplemetation. I did not find any implementation of interface request.
sorry about this question and thanks for help!
tom gong

The implementation of the interface request is left to the implementors of the Servlet container. So you can always treat it as a "class".
According to Sun:
"The servlet container creates an HttpServletRequest object and passes it as an argument to
the servlet's service methods (doGet, doPost, etc)."
Implementing an Interface in Java is not always the responsibility of the user of an application.

Thanks a lot, Tony
your help is appreciated.
tom gong