Web applications are configured with the <web-app> tag, which can occur in a number of places.

• WEB-INF/web.xml contains a top-level web-app element. It is the Servlet standard location for defining things like servlet mappings and security roles.
• WEB-INF/resin-web.xml is also used by Resin and will override and supplement the configuration in WEB-INF/web.xml. Use it to specify Resin specific configuration if you prefer to keep WEB-INF/web.xml strictly conforming to the Servlet specification.
• A web application can also be configured in the main Resin configuration, and in this context web-app is a child of <host>.