What is the config implicit object?

The config object is an object of type javax.servlet.ServletConfig. The ServletConfig for this JSP page. Has a page scope.

The config can be used to retrieve the configuration parameters that are specific to a JSP page. These parameters are set up within the deployment descriptor. To set up the configuration a servlet is configured within web.xml, please see How to config a JSP file in web.xml?.

The config object can be used to retrieve the ServletContext object through its getServletContext() method. Thus the following code retrieves information about the currently executing server, and in my own setup it generates the output.

<%
ServletContext ct = config.getServletContext();
out.print(ct.getServerInfo());
%>