Controlling Spring-Batch Step Flow in a java-config manner

Question

According to Spring-Batch documentation (http://docs.spring.io/spring-batch/2.2.x/reference/html/configureStep.html#controllingStepFlow), controlling step flow in an xml config file is very simple:

e.g. I could write the following job configuration:

<job id="myJob">
    <step id="step1">
        <fail on="CUSTOM_EXIT_STATUS"/>
        <next on="*" to="step2"/>
    </step>

    <step id="step2">
        <end on="1ST_EXIT_STATUS"/>
        <next on="2ND_EXIT_STATUS" to="step10"/>
        <next on="*" to="step20"/>
    </step>

    <step id="step10" next="step11" />
    <step id="step11" />

    <step id="step20" next="step21" />
    <step id="step21" next="step22" />
    <step id="step22" />
</job>

Is there a simple way defining such a job configuration in a java-config manner? (using JobBuilderFactory and so on...)

Michail Alexakis Michail Alexakis · Accepted Answer · 2017-09-14T00:51:51

As the documentation also mentions, we can only branch the flow based on the exit-status of a step. To be able to report a custom exit-status (possibly different from the one automatically mapped from batch-status), we must provide an afterStep method for a StepExecutionListener.

Suppose we have an initial step step1 (an instance of a Tasklet class Step1), and we want to do the following:

if step1 fails (e.g. by throwing a runtime exception), then the entire job should be considered as FAILED.
if step1 completes with an exit-status of COMPLETED-WITH-A, then we want to branch to some step step2a which supposedly handles this specific case.
otherwise, we stay on the main truck of the job and continue with step step2.

Now, provide an afterStep method inside Step1 class (also implementing StepExecutionListener):

private static class Step1 implements Tasklet, StepExecutionListener
{
    @Override
    public ExitStatus afterStep(StepExecution stepExecution)
    {
        logger.info("*after-step1* step-execution={}", stepExecution.toString());

        // Report a different exit-status on a random manner (just a demo!).
        // Some of these exit statuses (COMPLETED-WITH-A) are Step1-specific 
        // and are used to base a conditional flow on them.

        ExitStatus exitStatus = stepExecution.getExitStatus();
        if (!"FAILED".equals(exitStatus.getExitCode())) {
            double r = Math.random(); 
            if (r < 0.50)
                exitStatus = null; // i.e. COMPLETED
            else 
                exitStatus = new ExitStatus(
                    "COMPLETED-WITH-A", 
                    "Completed with some special condition A");
        }
        logger.info("*after-step1* reporting exit-status of {}", exitStatus);
        return exitStatus;
    }

    // .... other methods of Step1
}

Finally, build the job flow inside createJob method of our JobFactory implementation:

@Override
public Job createJob()
{
    // Assume some factories returning instances of our Tasklets
    Step step1 = step1(); 
    Step step2a = step2a();
    Step step2 = step2();

    JobBuilder jobBuilder = jobBuilderFactory.get(JOB_NAME)
        .incrementer(new RunIdIncrementer())
        .listener(listener);  // a job-level listener

    // Build job flow
    return jobBuilder
        .start(step1)
            .on("FAILED").fail()
        .from(step1)
            .on("COMPLETED-WITH-A").to(step2a)
        .from(step1)
        .next(step2)
        .end()
        .build();
}

Controlling Spring-Batch Step Flow in a java-config manner

2 Answers