import org.apache.twill.api.TwillApplication; //导入依赖的package包/类
@Override
public TwillPreparer prepare(TwillApplication application) {
  Preconditions.checkState(isRunning(), "Service not start. Please call start() first.");
  final TwillSpecification twillSpec = application.configure();
  final String appName = twillSpec.getName();

  return new YarnTwillPreparer(yarnConfig, twillSpec, yarnAppClient, zkClientService, locationFactory, jvmOptions,
                               new YarnTwillControllerFactory() {
    @Override
    public YarnTwillController create(RunId runId, Iterable<LogHandler> logHandlers,
                                      Callable<ProcessController<YarnApplicationReport>> startUp) {
      ZKClient zkClient = ZKClients.namespace(zkClientService, "/" + appName);
      YarnTwillController controller = listenController(new YarnTwillController(appName, runId, zkClient,
                                                                                logHandlers, startUp));
      synchronized (YarnTwillRunnerService.this) {
        Preconditions.checkArgument(!controllers.contains(appName, runId),
                                    "Application %s with runId %s is already running.", appName, runId);
        controllers.put(appName, runId, controller);
      }
      return controller;
    }
  });
}