public Map<String, Map<String, String>> getConfigurations() {
    Map<String, Map<String, String>> configurations = new HashMap<>();
    List<AmbariConfigurationEntity> entities = ambariConfigurationDAO.findAll();

    if (entities != null) {
      for (AmbariConfigurationEntity entity : entities) {
        String category = entity.getCategoryName();
        Map<String, String> configuration = configurations.computeIfAbsent(category, k -> new HashMap<>());
        configuration.put(entity.getPropertyName(), entity.getPropertyValue());
      }
    }

    return configurations;
  }
AmbariServerConfigurationHandler handles Ambari server specific configuration properties.
ambari-server/src/main/java/org/apache/ambari/server/controller/internal/AmbariServerConfigurationHandler.java