public void addRefreshCommands(Map<String, Map<String, String>> refreshCommands) {
    if (propertyComponentCommandMap == null) {
      propertyComponentCommandMap = new HashMap();
    }
    propertyComponentCommandMap.putAll(refreshCommands);
  }
If no command is defined for a component then the default command will be REFRESH_CONFIGS in case of a client component or
if there's only one command defined for an another component. This is because if RELOAD_CONFIGS is defined for NAMENODE then
presumably other dependent components will need just a refresh.
ambari-server/src/main/java/org/apache/ambari/server/state/RefreshCommandConfiguration.java