Simple HttpServlet that delegates to an HttpRequestHandler bean defined
in Spring's root web application context. The bean name must match the
HttpRequestHandlerServlet servlet-name as defined in web.xml.
This can for example be used to expose a single Spring remote exporter,
such as HttpInvokerServiceExporter and HessianServiceExporter, per
HttpRequestHandlerServlet definition. This is an alternative to defining
remote exporters as beans in a DispatcherServlet context, leveraging
the advanced mapping and interception facilities there.