Servlets :: Getting Path Of The Base URL?

I have a data.json in my J2EE web app.I need to load it either from local path when unit testing or from url when the server starts up.

so I've set it to get the local path by default and what I'm trying to do is that it is is running on a server, I'd like to change the path to a url.

Here is my code:

public String getUrlBase(HttpServletRequest request) {
URL requestUrl;
try {
requestUrl = new URL(request.getRequestURL().toString());
String portString = requestUrl.getPort() == -1 ? "" : ":" + requestUrl.getPort();
return requestUrl.getProtocol() + "://" + requestUrl.getHost() + portString + request.getContextPath() + "/";
} catch (MalformedURLException e) {
e.printStackTrace();
}
return null;
}

which works fine. The only issue is that I had to place this in the login page. Is there a way I can only set the path to the base url upon server start up?