Just use Spring type ClassPathResource.
File file = new ClassPathResource("countries.xml").getFile();
As long as this file is somewhere on classpath Spring will find it. This can be src/main/resources
during development and testing. In production, it can be current running directory.
EDIT: This approach doesn't work if file is in fat JAR. In such case you need to use:
InputStream is = new ClassPathResource("countries.xml").getInputStream();