@Override
  public Map<String, Object> resolve(InputStream in) throws ConfigurationResolveException {
    Yaml yaml = new Yaml();
    Map<String, Object> flattenedMap = new HashMap<String, Object>();
    Reader reader = null;
    try {
      reader = new UnicodeReader(in);
      for (Object object : yaml.loadAll(reader)) {
        if (object != null) {
          flattenedMap.putAll(getFlattenedMap(asMap(object)));
        }
      }
    } catch(YAMLException e) {
      throw new ConfigurationResolveException("parse yaml configuration failed.", e);
    } finally {
      if (reader != null) {
        try {
          reader.close();
        } catch (IOException e) {
          throw new ConfigurationResolveException("parse yaml configuration failed.", e);
        }
      }
    }
    return flattenedMap;
  }
The yaml property source resolver to resolve the environment configuration in yaml format.
src/main/java/com/eudemon/ratelimiter/env/resolver/YamlPropertySourceResolver.java