@Override
    public void start() {
        // Add this module as a user event listener so we can delete
        // all user properties when a user is deleted
        if (!provider.isReadOnly()) {
            UserEventDispatcher.addListener(eventHandler);
        }
    }
Returns the vCard of a given user or null if none was defined before. Changes to the
returned vCard will not be stored in the database. Use the returned vCard as a
read-only vCard.

@param username Username (not full JID) whose vCard to retrieve.
@return the vCard of a given user.
xmppserver/src/main/java/org/jivesoftware/openfire/vcard/VCardManager.java