This doesn't sound like an
Ant or Maven question, although if you're using Maven, there's a Maven-specific answer.
As far as accessing the file goes, it depends on how you intend to use the file. A webapp shouldn't be viewed as a directory subtree. Yes, when you construct it, you might lay out the components in a directory subtree, and URLs may LOOK like filesystem paths. But they're not.
You have 2 choices.
1. Put the config file OUTSIDE of the WEB-INF directory and open it via a URL reference, the same way you would to get an image, javascript or css file.
2. Put it inside WEB-INF/classes or in a jar inside the WEB-INFO/libs directory. That will place the file in your classpath. Then use the getResourceAsStream
servlet context method to read it.
If you don't want people to be able to pull up copies of the config file through their web browsers, use choice #2.