docs: private Cache getCache(PortletRequest req) {
          String cacheName = req.getPreferences().getValue(PREF_CACHE_NAME, DEFAULT_CACHE_NAME);
          if (StringUtils.isNotBlank(cacheName)) {
              log.debug("Looking up cache '{}'", cacheName);
              Cache cache = CacheManager.getInstance().getCache(cacheName);
              if (cache == null) {
                  throw new RuntimeException(
                          "Unable to find cache named "
                                  + cacheName
                                  + ". Check portlet preference value "
                                  + PREF_CACHE_NAME
                                  + " and configuration in ehcache.xml");
              }
              return cache;
          } else {
              log.debug(
                      "Portlet preference {} set to empty string; disabling caching for this portlet instance",
                      PREF_CACHE_NAME);
              return null;
          }
      }