How to redirect to a "Maintenance Mode" page if context is missing

I have a webapp deployed with a war archive on a tomcat 6 server. There is a clean way to instrument Tomcat to redirect to a "Maintenance Mode" page if my webapps is undeployed?

I mean some sort of Tomcat component that dinamically intercept all request to my webapp开发者_如何学Python and redirect them to another webapp (maybe ROOT) page to inform my users that the application is temporarily down.

Install Apache HTTPD which uses Tomcat Connector to proxy the requests to Tomcat and configure Apache HTTPD to display the maintenance page as 404/503 error page.