archaius-core/src/main/java/com/netflix/config/jmx/BaseConfigMBean.java
@Override
	public void addProperty(String key, String value) {
        if (config instanceof ConcurrentCompositeConfiguration) {
            ((ConcurrentCompositeConfiguration) config).setOverrideProperty(key, value);
        } else {
		    config.addProperty(key, value);
        }
	}
@Override
	public void addProperty(String key, String value) {
        if (config instanceof ConcurrentCompositeConfiguration) {
            ((ConcurrentCompositeConfiguration) config).setOverrideProperty(key, value);
        } else {
		    config.addProperty(key, value);
        }
	}
Calls <code>config.addrProperty()</code>. If the underlying configuration
is {@link ConcurrentCompositeConfiguration}, it calls {@link ConcurrentCompositeConfiguration#setOverrideProperty(String, Object)}
instead.