* @return the file timestamp in milliseconds, or -1 if not determinable
*/
protected long getFileTimestamp(String resourceUrl) {
ServletContextResource resource = new ServletContextResource(getServletContext(), resourceUrl);
try {
long lastModifiedTime = resource.lastModified();
if (logger.isDebugEnabled()) {
logger.debug("Last-modified timestamp of " + resource + " is " + lastModifiedTime);
}
return lastModifiedTime;
}