### 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">

invoker = cluster.join(new StaticDirectory(invokers));
                }
            }
        }
        Boolean c = check;
        if (c == null && consumer != null) {
            c = consumer.isCheck();
        }
        if (c == null) {
            c = true; 
        }
        if (c && !invoker.isAvailable()) {
            throw new IllegalStateException("Failed to check the status of the service " + interfaceName + ". No provider available for the service " + (group == null ? "" : group + "/") + interfaceName + (version == null ? "" : ":" + version) + " from the url " + invoker.getUrl() + " to the consumer " + NetUtils.getLocalHost() + " use dubbo version " + Version.getVersion());
        }
        if (logger.isInfoEnabled()) {
            logger.info("Refer dubbo service " + interfaceClass.getName() + " from url " + invoker.getUrl());
        }
        
        return (T) proxyFactory.getProxy(invoker);
    }
    private void checkDefault() {
        if (consumer == null) {
            consumer = new ConsumerConfig();
        }
        appendProperties(consumer);
    }
    public Class<?> getInterfaceClass() {
        if (interfaceClass != null) {
            return interfaceClass;
        }