@Override
        protected Map<String, String> merge(ConfigKey key, List<Map<String, String>> values) {
            Map<String, String> merged = null;

            // Iterate in reverse, the first entry in values has highest priority
            for(int i = values.size() - 1; i >= 0; i--) {
                Map<String, String> value = values.get(i);
                if(merged == null) {
                    merged = new HashMap<>(value);
                } else {
                    merged.putAll(value);
                }
            }
            return merged;
        }
Data type-specific extractor to read value from properties.

@param prefix
@param key
@param properties
@return
src/main/java/io/fabric8/maven/docker/config/handler/property/ValueProvider.java