从引导 Spring 批量应用 ItemWriter 的 @BeforeStep 方法调用 ItemProcessor 的 @BeforeStep 方法之前

Question

I'm studing SpringBatch, I have a problem during the boot Spring call ItemWriter before ItemProcessor. Why?

public class PollingReader implements ItemReader<File> {
    @BeforeStep
    public void beforeStep(StepExecution stepExecution) throws NotDirectoryException {..}
    @AfterStep
    public ExitStatus afterStep(StepExecution stepExecution) {..}
}
    
public class PollingWriter implements ItemWriter<File> {
    @BeforeStep
    public void beforeStep(StepExecution stepExecution) {..}
    @AfterStep
    public ExitStatus afterStep(StepExecution stepExecution) {..}
..
}

public class PollingProcessor implements ItemProcessor<File, File> {
    @BeforeStep
    public void beforeStep(StepExecution stepExecution) {..}
    @AfterStep
    public ExitStatus afterStep(StepExecution stepExecution) {..}
}

And the method of the @AfterStep ItemProcessor is called before of the method @AfterStep ItemWriter.

I expected this cycle call for @BeforeStep:

• ItemReader
• ItemProcessor
• ItemWriter

but I have this result:

• ItemReader
• ItemWriter
• ItemProcessor

and for @AfterStep I expected:

• ItemWriter
• ItemProcessor
• ItemReader.

but I have this result:

• ItemProcessor
• ItemWriter
• ItemReader

Thanks:)

Answer 1

Your objects are polymorphic: they are both item reader/processor/writer and StepExecutionListener s (as proxies, to be more precise). When Spring Batch runs StepExecutionListeners before/after a step, it does not see them as reader/processor/writer, and the order of their execution is not necessarily the same as they are called in a chunk-oriented step (in fact, the order is undefined in that case).