code: private VariantResolver registerResolver(VariantResolver defaultResolver, String configPropertyName) {
  		VariantResolver resolver = null;
  		if (configProperties.getProperty(configPropertyName) == null) {
  			resolver = defaultResolver;
  		} else {
  			resolver = (VariantResolver) ClassLoaderResourceUtils
  					.buildObjectInstance(configProperties.getProperty(configPropertyName));
  		}
  
  		this.generatorRegistry.registerVariantResolver(resolver);
  		return resolver;
  	}
docs: Register a resolver in the generator registry
  
  @param defaultResolver
  the default resolver
  @param configPropertyName
  the configuration property whose the value define the resolver
  class
  @return