getClass().getClassLoader().getResourceAsStream() is caching the resource

To avoid caching you can use:

getClass().getClassLoader().getResource().openStream()

It would be equal to using URLResourceLoader for Velocity instead of ClasspathResourceLoader I suppose. I would just go with a file loader.

See if something like this helps (exception handling omitted):

URL res = getClass().getClassLoader().getResource(resName);
if (res != null) {
    URLConnection resConn = res.openConnection();
    resConn.setUseCaches(false);
    InputStream in = resConn.getInputStream();
}