How to monitor the progress of a Tasklet to send to the GUI ?

[cblin]

Here is my spring batch config (relevant part) :

    <batch:job id="fakeJob" parent="simpleJob">
        <batch:step id="fakeLongJobStep" parent="simpleStep">
            <batch:tasklet ref="mytasklet" />
        </batch:step>
    </batch:job>

So this is just a job calling one step which is a tasklet.

What I want to do is to report the progress inisde the tasklet.

At first, I tried :

public class MyTasklet implements Tasklet {   
    @Override
    public RepeatStatus execute(StepContribution contribution, ChunkContext chunkContext) throws Exception {
        JobExecution e = chunkContext.getStepContext().getStepExecution().getJobExecution();
        for (i = 0; i < 100; i++) {
             e.getExecutionContext().put("progress", i+"/100");
             Thread.sleep(2000); //simulate heavy operation
        }
    }
}

Then, from another thread (i.e another XHR request to my webapp), I ask for the current progress :

   public String readProgress(int executionId) {
     return jobExplorer.getJobExcution(executionId).getExecutionContext().get("progress"); 
   }

This always return null except when the job is finished (which then report 99/100)

From what I understand, this is logical since the JobExecution is NOT persisted during the execution of a step (only persisted after).
How can I do to track the progress ?

The first thing I tried was to inject JobRepository into my tasklet and call jobRepository.updateExecutionContext(jobExecution) .
I assume this does not work since the transaction is not commited (hence, other threads still do not see the progress).
So how can I do ? Should I use a TransactionTemplate for each heavy operation or something like that ?

Please, note that using the reader->writer paradigm is not possible in my case (ask details if you need to know why ).