and why do you need one?
A Servlet engine is software that extends/"hooks
into" web server software such as Microsoft's
Internet Information Server (IIS) or Apache,
allowing Java programs (servlets) to quickly process
web browser requests and dynamically generate custom
For instance, ArcIMS generates data for maps requested by users over the web. But, without a Servlet engine, ArcIMS would not be able to receive the requests nor deliver the resulting maps to the user's web browser.