@Override
  @JsonIgnore
  public String getId() {
    String id = getGroup();
    if (isCluster(id)) {
      id = CLUSTER;
    }
    return id;
  }
Returns {@link #getGroup()} or {@link AbstractConfiguration#CLUSTER} if group is null.
geode-management/src/main/java/org/apache/geode/management/configuration/GatewayReceiver.java