public String getServiceName() {
    return serviceName;
  }
Gets the name of the service. This is only applicable when
{@link #isDefault()} is {@code true}.

@return the service that this is the default group for, or {@code null} if
        this is not a default group.
ambari-server/src/main/java/org/apache/ambari/server/orm/entities/AlertGroupEntity.java