Create a new @FlowScope

[mcherb]

Context

I want to share a bean between different steps of the same flow (and dies just after the flow has ended). I wanted to use the @JobScope but it doesn't support multi-threading. I'm wondering if we can add a @FlowScope which support multi-threading.

[fmbenhassine]

Thank you for requesting this feature. I like the idea, but I would like to see a real world use case. Can you please share an example?

I wanted to use the @JobScope but it doesn't support multi-threading

Are you intending to use the flow-scoped bean in a multi-threaded setup? We would have the same issue with the job scope..

[mcherb]

Thanks for your replay :)

My use-case is like the following:

class Shared {
    Map<> state = concurrentMap();
}

@Bean
Shared myFlowState() {
  return new Shared();
}

@Bean
Step step1(Shared myFlowState, TaskExecutor taskExecutor) {
  return new StepBuilder("step1", ...)
              .chunk(....)
              .reader(...)
              .processor(/*fill the state of myFlowState*/)
              .writer(...)
              .taskExecutor(taskExecutor)
              .build();
}

@Bean
Step step2(Shared myFlowState) {
  return new StepBuilder("step1", ...)
              .tasklet(/*read the state of myFlowState*/)
              .build();
}


@Bean
Flow flow() {
  return new FlowBuilder<Flow>("myFlow")
                      .start(step1(null, null))
                      .next(step2(null))
                      .build();
}

Once the flow is done, I want to get rid of the myFlowState bean. Its state is huge and will be kept in the memory till the end of the job.

Now, imagine that, the Shared been wants to access to the jobParameters like the following :

@Bean
Shared myFlowState(@Value("#{jobParameters['param']}") Any param) {
  return new Shared(param);
}

@StepScope won't do it, because I loose the state at the end of the Step. @JobScope will throw an exception because of the taskExecutor (multi-threading) on step1, Am I right ?

[quaff]

I encountered the same issue with @JobScope and parallel flows, I guess it's caused by flow is not executed by the thread started job, and job scope is implemented by ThreadLocal which rely on same thread, am I right?