docs: protected boolean checkIfUnmodifiedSince(final HttpServletRequest request, final HttpServletResponse response, final Attributes resourceAttributes)
  			throws IOException {
  		try {
  			final long lastModified = resourceAttributes.getLastModified();
  			final long headerValue = request.getDateHeader("If-Unmodified-Since");
  			if (headerValue != -1) {
  				if (lastModified >= (headerValue + 1000)) {
  					// The entity has not been modified since the date
  					// specified by the client. This is not an error case.
  					response.sendError(HttpServletResponse.SC_PRECONDITION_FAILED);
  					return false;
  				}
  			}
  		} catch (final IllegalArgumentException illegalArgument) {
  			return true;
  		}
  		return true;
  	}