Running multiple instances of spring batch job in parallel

Question

I have a Job for monthly invoicing. Current job consist from few Steps. I am passing data between Steps using StepExecution and ExecutionContextPromotionListener. We are going to run Job for each invoice. So we will have multiple instances of a job in parallel which pass data between Steps .

implements ItemWriter<Invoice> {
 @BeforeStep
  public void saveStepExecution(StepExecution stepExecution) {
    this.stepExecution = stepExecution;
  }
}

@Bean
  public ExecutionContextPromotionListener promotionListener() {
    ExecutionContextPromotionListener listener = new ExecutionContextPromotionListener();
    listener.setKeys(new String[] {"invoice"});
    return listener;
  }

I am pretty sure it`s not thread safe. Could somebody advise any solution for Spring Batch?

Any advice or explanation if I am wrong