It would be nice to add some improvements to the CacheFilter class in order to make it easier to have a sub-class.

/**
     * doFilterPreProcess is a method allowing subclass to perform actions
     * at the start of the filtering process.
     *
     * @param request The HTTP servlet request
     * @param response The HTTP servlet response
     * @param key The cache key used to access the cache
     * @param cache The cache object
     */
    protected void doFilterPreProcess(HttpServletRequest request,
                                      HttpServletResponse response,
                                      String key,
                                      Cache cache) {
        
if (log.isDebugEnabled()) {
            log.debug("<cache>: doFilter for key " + key + " is starting.");
        }
    }

/**
     * doFilterPostProcess is a method allowing subclass to perform actions
     * at the end of the filtering process.
     *
     * @param request The HTTP servlet request
     * @param response The HTTP servlet response
     * @param key The cache key used to access the cache
     * @param cache The cache object
     */
    protected void doFilterPostProcess(HttpServletRequest request,
                                       HttpServletResponse response,
                                       String key,
                                       Cache cache) {
        if (log.isDebugEnabled()) {
            log.debug("<cache>: doFilter for key " + key + " has been done.");
        }
    }