How to trigger a scheduled Spring Batch Job?

Question

I want to be able to start my job with a REST controller, then when the job is started, it should run on a scheduled basis, until i stop it again with REST.

So this is m

Answer 1

In first you are defining the job:

@Bean
@Qualifier("fancyScheduledJob")
public Job job() {
    return jobBuilderFactory.get("job")
            .incrementer(new RunIdIncrementer())
            .flow(step1())
            .end()
            .build();
}

In second you are initiating the execution of this job:

@Autowired
@Qualifier(value = "fancyScheduledJob")
private Job job;

@Autowired
private JobLauncher jobLauncher;

@Scheduled(cron = "0/5 * * * * ?")
public void launch() throws JobParametersInvalidException, JobExecutionAlreadyRunningException, JobRestartException, JobInstanceAlreadyCompleteException, JobInstanceAlreadyExistsException, NoSuchJobException {

    jobLauncher.run(job, JobParametersBuilder()
            .addLong("launchTime", System.currentTimeMillis())
            .toJobParameters())
}

Also note that the "launchTime" paramter is introduced: by default spring batch is preventing launching the job with same parameter values.

While your schedule is quite tight - every 5 seconds you should be aware of concurrency. Or if you want to be assured that at each and every moment only 1 instance of the job is executed you can configure custom single threaded job launcher:

@Bean(name = "fancyJobExecutorPool")
public TaskExecutor singleThreadedJobExecutorPool() {
    ThreadPoolTaskExecutor executor = new ThreadPoolTaskExecutor();
    executor.setCorePoolSize(1);
    executor.setMaxPoolSize(1);
    executor.setQueueCapacity(100500);
    executor.setThreadNamePrefix("fancy-job-batch-");
    return executor;
}

@Bean(name = "fancyJobLauncher")
public JobLauncher singleThreadedJobLauncher(JobRepository jobRepository)
{
    SimpleJobLauncher sjl = new SimpleJobLauncher();
    sjl.setJobRepository(jobRepository);
    sjl.setTaskExecutor(singleThreadedJobExecutorPool());
    return sjl;
}

And use this single threaded job launcher during launch time.

@Autowired
@Qualifier("fancyJobLauncher")
private JobLauncher jobLauncher;

With this your job instances will be executed one by one (but this doesn't limits parallel execution of steps inside of your job).