In many batch scenarios, finding no rows in a database or file to
process is not exceptional. The Step is simply
considered to have found no work and completes with 0 items read. All of
the ItemReader implementations provided out of the
box in Spring Batch default to this approach. This can lead to some
confusion if nothing is written out even when input is present. (which
usually happens if a file was misnamed, etc) For this reason, the meta
data itself should be inspected to determine how much work the framework
found to be processed. However, what if finding no input is considered
exceptional? In this case, programmatically checking the meta data for no
items processed and causing failure is the best solution. Because this is
a common use case, a listener is provided with just this
functionality:
public class NoWorkFoundStepExecutionListener extends StepExecutionListenerSupport {
public ExitStatus afterStep(StepExecution stepExecution) {
if (stepExecution.getReadCount() == 0) {
return ExitStatus.FAILED;
}
return null;
}
}
The above StepExecutionListener inspects the
readCount property of the StepExecution during the
'afterStep' phase to determine if no items were read. If that is the case,
an exit code of FAILED is returned, indicating that the
Step should fail. Otherwise, null is returned,
which will not affect the status of the
Step.