If you're hosting on a web server that requires Apache to be the front-end, like using it as a virtual domain host for multiple domains, chances are it'll be difficult for you to swap Apache with any other web server, especially if the other domains are happily hosted without a problem. But what if you are required to use some other app servers without taking away Apache instead?
The configuration assumes that your alternate app server is hosted on the same server on port 8080 as indicated, given that port 80 is already occupied by Apache. Otherwise this should allow all connections to be transparently forwarded to your new app server without losing functionality of your existing hosts.