@Override
  protected void validate(StackAdvisorRequest request)
    throws StackAdvisorException {
    if (request.getHosts() == null || request.getHosts().isEmpty()
      || request.getServices() == null || request.getServices().isEmpty()
      || request.getChangedConfigurations() == null
      || request.getChangedConfigurations().isEmpty()) {
      throw new StackAdvisorException("Hosts, services and changed-configurations must not be empty");
    }
  }
{@link StackAdvisorCommand} implementation for
configuration dependencies recommendation.
ambari-server/src/main/java/org/apache/ambari/server/api/services/stackadvisor/commands/ConfigurationDependenciesRecommendationCommand.java