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.

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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.