private Boolean getHasSharedGroupsFromCache() {
        synchronized (sharedGroupMetaCache) {
            final Object value = sharedGroupMetaCache.get(HAS_SHARED_GROUPS_KEY);
            if (value == null) {
                return null;
            } else {
                return (Boolean) value;
            }
        }
    }
Returns a custom {@link Map} that updates the database whenever
a property value is added, changed, or deleted.

@param group The target group
@return The properties for the given group
xmppserver/src/main/java/org/jivesoftware/openfire/group/AbstractGroupProvider.java