### ReferenceConfig#init , at line 307
change : prifix -> prefix
<img width="746" alt="1" src="https://user-images.githubusercontent.com/6971152/35309902-a22d3ed2-00e9-11e8-9928-e394b9e3d632.png">

### by the way,  ReferenceConfig#setInterface , at line 476
it's no need to cast null to String
<img width="903" alt="2" src="https://user-images.githubusercontent.com/6971152/35309908-b09e4a92-00e9-11e8-9725-8e6ff8071370.png">

}
        if (ref == null) {
            init();
        }
        return ref;
    }
    public synchronized void destroy() {
        if (ref == null) {
            return;
        }
        if (destroyed) {
            return;
        }
        destroyed = true;
        try {
            invoker.destroy();
        } catch (Throwable t) {
            logger.warn("Unexpected err when destroy invoker of ReferenceConfig(" + url + ").", t);
        }
        invoker = null;
        ref = null;
    }
    private void init() {
        if (initialized) {
            return;
        }
        initialized = true;
        if (interfaceName == null || interfaceName.length() == 0) {
            throw new IllegalStateException("<dubbo:reference interface=\"\" /> interface not allow null!");
        }