@Override
    public void initialize() throws InitializationException {
        this.registry = new HashMap<>();
        for (ExternalConfigHandler handler : new ExternalConfigHandler[] { propertyConfigHandler, dockerComposeConfigHandler }) {
            if (handler != null) {
                registry.put(handler.getType(), handler);
            }
        }
    }
Manager holding all config handlers for external configuration

@author roland
@since 18/11/14
src/main/java/io/fabric8/maven/docker/config/handler/ImageConfigResolver.java