//we set caching headers before we try and serve from the cache
if (cachable && cacheTime != null) {
    exchange.getResponseHeaders().put(Headers.CACHE_CONTROL, "public, max-age=" + cacheTime);
    if (System.currentTimeMillis() > lastExpiryDate) {
        long date = System.currentTimeMillis();
        lastExpiryHeader = DateUtils.toDateString(new Date(date));
        lastExpiryDate = date;
    }
    exchange.getResponseHeaders().put(Headers.EXPIRES, lastExpiryHeader);
}