Passing info between steps in Spring?

Question

I'm trying to make a Spring Batch and I have no experience with it.

Is it possible to pass information from each batch step or must they be completely independent?

For example if I have

   <batch:step id="getSQLs" next="runSQLs">
        <batch:tasklet transaction-manager="TransactionManager"
            ref="runGetSQLs" />
    </batch:step>

    <batch:step id="runSQLs">
        <batch:tasklet transaction-manager="TransactionManager"
            ref="runRunSQLs" />
    </batch:step>

And getSQLs triggers a bean which executes a class which generates a List of type String. Is it possible to reference that list for the bean triggered by runSQLs? ("triggered" may not be the right term but I think you know what I mean)

UPDATE: So getSQLs step triggers this bean:

<bean id="runGetSQLs" class="myTask"
    scope="step">
    <property name="filePath" value="C:\Users\username\Desktop\sample.txt" />
</bean>

which triggers myTask class which executes this method:

  @Override
public RepeatStatus execute(StepContribution contribution, ChunkContext chunkContext) throws Exception {

    ExecutionContext stepContext = this.stepExecution.getExecutionContext();
    stepContext.put("theListKey", sourceQueries);

    return RepeatStatus.FINISHED;
}

Do I need to somehow pass stepExecution to the execute method?

Answer 1

Spring Batch supports pushing data to future job steps, and this can be done through the ExecutionContext, more precisely the JobExecutionContext. Here I'm referring to example from the official documentation, as it is the ultimate reference for me:

To make the data available to future Steps, it will have to be "promoted" to the Job ExecutionContext after the step has finished. Spring Batch provides the ExecutionContextPromotionListener for this purpose.

The listener should be configured with your step, the one sharing data with future ones:

<batch:step id="getSQLs" next="runSQLs">
    <batch:tasklet transaction-manager="TransactionManager"
        ref="runGetSQLs" />
    <listeners>
        <listener>
            <beans:bean id="promotionListener" class="org.springframework.batch.core.listener.ExecutionContextPromotionListener">
                <beans:property name="keys" value="theListKey"/>
            </beans:bean>
        </listener>
    </listeners>
</batch:step>

<batch:step id="runSQLs">
    <batch:tasklet transaction-manager="TransactionManager"
        ref="runRunSQLs" />
</batch:step>

The data should be populated from your execution code block as follows:

// ...
ExecutionContext stepContext = this.stepExecution.getExecutionContext();
stepContext.put("theListKey", yourList);

Then in subsequent steps, this List can be retrieved with a post computation hook annotated with @BeforeStep a as follows:

@BeforeStep
public void retrieveSharedData(StepExecution stepExecution) {
    JobExecution jobExecution = stepExecution.getJobExecution();
    ExecutionContext jobContext = jobExecution.getExecutionContext();
    this.myList = jobContext.get("theListKey");
}