Spring Batch - Job 개념

// org.springframework.batch.core.job.AbstractJob
abstract protected void doExecute(JobExecution execution) throws JobExecutionException;

@Override
public final void execute(JobExecution execution) {

	Assert.notNull(execution, "jobExecution must not be null");
	execution.getExecutionContext().put(SpringBatchVersion.BATCH_VERSION_KEY, SpringBatchVersion.getVersion());

  ...

	try (Observation.Scope scope = observation.openScope()) {

		jobParametersValidator.validate(execution.getJobParameters());

		if (execution.getStatus() != BatchStatus.STOPPING) {

			execution.setStartTime(LocalDateTime.now());
			updateStatus(execution, BatchStatus.STARTED);

			listener.beforeJob(execution);

			try {
				doExecute(execution);

        ...

// org.springframework.batch.core.job.SimpleJob#doExecute
@Override
protected void doExecute(JobExecution execution)
  throws JobInterruptedException, JobRestartException, StartLimitExceededException {

  StepExecution stepExecution = null;
  for (Step step : steps) {
    stepExecution = handleStep(step, execution);
    if (stepExecution.getStatus() != BatchStatus.COMPLETED) {
      //
      // Terminate the job if a step fails
      //
      break;
    }
  }

  //
  // Update the job status to be the same as the last step
  //
  if (stepExecution != null) {
    if (logger.isDebugEnabled()) {
      logger.debug("Upgrading JobExecution status: " + stepExecution);
    }
    execution.upgradeStatus(stepExecution.getStatus());
    execution.setExitStatus(stepExecution.getExitStatus());
  }
}

// org.springframework.batch.core.repository.dao.JdbcJobInstanceDao#createJobInstance

@Override
public JobInstance createJobInstance(String jobName, JobParameters jobParameters) {

  Assert.notNull(jobName, "Job name must not be null.");
  Assert.notNull(jobParameters, "JobParameters must not be null.");

  Assert.state(getJobInstance(jobName, jobParameters) == null, "JobInstance must not already exist");

  Long jobInstanceId = jobInstanceIncrementer.nextLongValue();

  JobInstance jobInstance = new JobInstance(jobInstanceId, jobName);
  jobInstance.incrementVersion();

  Object[] parameters = new Object[] { jobInstanceId, jobName, jobKeyGenerator.generateKey(jobParameters),
    jobInstance.getVersion() };
  getJdbcTemplate().update(getQuery(CREATE_JOB_INSTANCE), parameters,
    new int[] { Types.BIGINT, Types.VARCHAR, Types.VARCHAR, Types.INTEGER });

  return jobInstance;
}

// org.springframework.batch.core.launch.support.TaskExecutorJobLauncher#run
jobExecution = jobRepository.createJobExecution(job.getName(), jobParameters);

		try {
			taskExecutor.execute(new Runnable() {

				@Override
				public void run() {
            ...
						job.execute(jobExecution);

// org.springframework.batch.core.job.SimpleStepHandler#handleStep
JobInstance jobInstance = execution.getJobInstance();

StepExecution lastStepExecution = jobRepository.getLastStepExecution(jobInstance, step.getName());
if (stepExecutionPartOfExistingJobExecution(execution, lastStepExecution)) {
	// If the last execution of this step was in the same job, it's
	// probably intentional so we want to run it again...
	if (logger.isInfoEnabled()) {
		logger.info(String.format(
				"Duplicate step [%s] detected in execution of job=[%s]. "
						+ "If either step fails, both will be executed again on restart.",
				step.getName(), jobInstance.getJobName()));
	}
	lastStepExecution = null;
}
StepExecution currentStepExecution = lastStepExecution;

if (shouldStart(lastStepExecution, execution, step)) {
  ...
}

// org.springframework.batch.core.job.SimpleStepHandler#shouldStart
protected boolean shouldStart(StepExecution lastStepExecution, JobExecution jobExecution, Step step)
		throws JobRestartException, StartLimitExceededException {

	BatchStatus stepStatus;
	if (lastStepExecution == null) {
		stepStatus = BatchStatus.STARTING;
	}
	else {
		stepStatus = lastStepExecution.getStatus();
	}

  ...

	if ((stepStatus == BatchStatus.COMPLETED && !step.isAllowStartIfComplete())
			|| stepStatus == BatchStatus.ABANDONED) {
		// step is complete, false should be returned, indicating that the
		// step should not be started
		if (logger.isInfoEnabled()) {
			logger.info("Step already complete or not restartable, so no action to execute: " + lastStepExecution);
		}
		return false;
	}

  ...

}

// org.springframework.batch.core.repository.support.SimpleJobRepository#createJobExecution
@Override
public JobExecution createJobExecution(String jobName, JobParameters jobParameters)
		throws JobExecutionAlreadyRunningException, JobRestartException, JobInstanceAlreadyCompleteException {

	Assert.notNull(jobName, "Job name must not be null.");
	Assert.notNull(jobParameters, "JobParameters must not be null.");

	JobInstance jobInstance = jobInstanceDao.getJobInstance(jobName, jobParameters);
	ExecutionContext executionContext;

	if (jobInstance != null) {

		List<JobExecution> executions = jobExecutionDao.findJobExecutions(jobInstance);

		if (executions.isEmpty()) {
			throw new IllegalStateException("Cannot find any job execution for job instance: " + jobInstance);
		}

		for (JobExecution execution : executions) {
			if (execution.isRunning()) {
				throw new JobExecutionAlreadyRunningException(
						"A job execution for this job is already running: " + jobInstance);
			}

      ...
		}
		executionContext = ecDao.getExecutionContext(jobExecutionDao.getLastJobExecution(jobInstance));
	}

  ...

	return jobExecution;

}

// org.springframework.batch.core.BatchStatus
public enum BatchStatus {

  /**
   * The batch job has successfully completed its execution.
   */
  COMPLETED,
  /**
   * Status of a batch job prior to its execution.
   */
  STARTING,
  /**
   * Status of a batch job that is running.
   */
  STARTED,
  /**
   * Status of batch job waiting for a step to complete before stopping the batch job.
   */
  STOPPING,
  /**
   * Status of a batch job that has been stopped by request.
   */
  STOPPED,
  /**
   * Status of a batch job that has failed during its execution.
   */
  FAILED,
  /**
   * Status of a batch job that did not stop properly and can not be restarted.
   */
  ABANDONED,
  /**
   * Status of a batch job that is in an uncertain state.
   */
  UNKNOWN;

  public boolean isRunning() {
    return this == STARTING || this == STARTED || this == STOPPING;
  }

  ...

}