Spring Batch：在读取器和写入器之间传递数据

Question

LOG.info("INSIDE WRITE, NPAG: " + nPag);

@Component
public class LCItemReader implements ItemReader<String> {

private StepExecution stepExecution;

private int nPag = 1;

@Override
public String read() throws CustomItemReaderException {

    ExecutionContext stepContext = this.stepExecution.getExecutionContext();
    stepContext.put("npag", nPag);
    nPag++;
    return "content";
}

@BeforeStep
public void saveStepExecution(StepExecution stepExecution) {
    this.stepExecution = stepExecution;
}
}

@Component
@StepScope
public class LCItemWriter implements ItemWriter<String> {

private String nPag;

@Override
public void write(List<? extends String> continguts) throws Exception {
    try {
        LOG.info("INSIDE WRITE, NPAG: " + nPag);
    } catch (Throwable ex) {
        LOG.error("Error: " + ex.getMessage());
    }
}

@BeforeStep
public void retrieveInterstepData(StepExecution stepExecution) {
    JobExecution jobExecution = stepExecution.getJobExecution();
    ExecutionContext jobContext = jobExecution.getExecutionContext();
    this.nPag = jobContext.get("npag").toString();
}
}

@Bean
public Job lCJob() {
    return jobs.get("lCJob")
            .listener(jobListener)
            .start(lCStep())
            .build();
}

@Bean
public Step lCStep() {
    return steps.get("lCStep")
            .<String, String>chunk(1)
            .reader(lCItemReader)
            .processor(lCProcessor)
            .writer(lCItemWriter)
            .listener(promotionListener())
            .build();
}

听众

@Bean
public ExecutionContextPromotionListener promotionListener() {
    ExecutionContextPromotionListener executionContextPromotionListener = new ExecutionContextPromotionListener();
    executionContextPromotionListener.setKeys(new String[]{"npag"});
    return executionContextPromotionListener;
}

Answer 1

ExecutionContextPromotionListener特别声明它在步骤结束时工作，因此在编写器执行之后。所以，我认为你指望的晋升不会在你认为它会发生的时候发生。

如果我是你，我会在步骤上下文中设置它，如果你需要一个步骤中的值，我会从步骤中获取它。否则，我会将其设置为作业上下文。

另一个方面是@beforestep。它标记要在步骤上下文存在之前执行的方法。在读取器中设置nPag值的方式应该是在步骤开始执行之后。