Storing in JobExecutionContext from tasklet and accessing in another tasklet

Question

I have a requirement in which a tasklet, stores all the files in the directories in an arraylist. The size of the list is stored in the job execution context. Later this count is accessed from another tasklet in another step. How do it do this. I tried to store in jobexecution context, at runtime throws unmodifiable collection exception,

public RepeatStatus execute(StepContribution arg0, ChunkContext arg1)
throws Exception {
    StepContext stepContext = arg1.getStepContext();
    StepExecution stepExecution = stepContext.getStepExecution();
    JobExecution jobExecution = stepExecution.getJobExecution();
    ExecutionContext jobContext = jobExecution.getExecutionContext();
     jobContext.put("FILE_COUNT",150000);

also stored the stepexection reference in beforestep annotation .still not possioble.kindly let me know ,how to share data between two tasklets.

Answer 1

you have at least 4 possibilities:

1. use the ExecutionPromotionListener to pass data to future steps
2. use a (spring) bean to hold inter-step data, e.g. a ConcurrentHashMap
   • without further action this data won't be accessible for a re-start
3. access the JobExecutionContext in your tasklet, should be used with caution, will cause thread problems for parallel steps
4. use the new jobscope (introduced with spring batch 3)

Code Example for accessing JobExecution from Tasklet:

1. setting a value

   public class ChangingJobExecutionContextTasklet implements Tasklet {
   
       /** {@inheritDoc} */
       @Override
       public RepeatStatus execute(StepContribution contribution, ChunkContext chunkContext) throws Exception {
           // set variable in JobExecutionContext
           chunkContext
                   .getStepContext()
                   .getStepExecution()
                   .getJobExecution()
                   .getExecutionContext()
                   .put("value", "foo");
   
           // exit the step
           return RepeatStatus.FINISHED;
       }
   
   }
   

2. extracting a value

   public class ReadingJobExecutionContextTasklet implements Tasklet {
   
       private static final Logger LOG = LoggerFactory.getLogger(ChangingJobExecutionContextTasklet.class);
   
       /** {@inheritDoc} */
       @Override
       public RepeatStatus execute(StepContribution contribution, ChunkContext chunkContext) throws Exception {
           // pull variable from JobExecutionContext
           String value = (String) chunkContext
                                       .getStepContext()
                                       .getStepExecution()
                                       .getJobExecution()
                                       .getExecutionContext()
                                       .get("value");
   
           LOG.debug("Found value in JobExecutionContext:" + value);
   
           // exit the step
           return RepeatStatus.FINISHED;
       }
   }
   

i created code examples for the first 3 solutions in my spring-batch-examples github repository, see module complex and package interstepcommunication

Answer 2

Another way is to use StepExecutionListener which is called after step execution. Your tasklet can implements it and share local attribute.

public class ReadingJobExecutionContextTasklet implements Tasklet, StepExecutionListener {
    private String value;

    @Override
    public ExitStatus afterStep(StepExecution stepExecution) {
        ExecutionContext jobExecutionContext = stepExecution.getJobExecution().getExecutionContext();

        jobExecutionContext.put("key", value);
        //Return null to leave the old value unchanged.
        return null;
    }
}

So, in the step, your bean is a tasklet and a listener like bellow. You should also configure the scope of you step to "step" :

    <batch:step id="myStep" next="importFileStep">
        <batch:tasklet>
            <ref bean="myTasklet"/>
            <batch:listeners>
                <batch:listener ref="myTasklet"/>
            </batch:listeners>
        </batch:tasklet>
    </batch:step>

    <bean id="myTasklet" class="ReadingJobExecutionContextTasklet" scope="step">