Spring Batch - how to fail a job when the ItemReader returns no data

问题

I have a spring batch application which reads data from a DB table with JdbcCursorItemReader and writes it to a flat file with FlatFileItemWriter.

When I test my application, I see that the FlatFileItemWriter creates a file even if no data is returned from the DB via JdbcCursorItemReader. However, I'm planning to fail my job when there is no appropriate data in DB. Is it possible to do so or at least prevenet FlatFileItemWriter from creating a file?

Regards

回答1:

from http://static.springsource.org/spring-batch/reference/html/patterns.html

11.7. Handling Step Completion When No Input is Found

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;
}

}

回答2:

Is it possible to do so or at least prevent FlatFileItemWriter from creating a file?

For the second part your of your question FlatFileItemWriter has a flag to delete the file if nothing is written.

shouldDeleteIfEmpty : Flag to indicate that the target file should be deleted if no lines have been written (other than header and footer) on close.

回答3:

ItemReadListener's afterRead method will be called even if there is no data. You can probably put what you wanted over there.

回答4:

ItemProcessor will only be called if the ItemReader returns an object. Null value is used to indicate processing is finished.

Do not use null value as an error indication : it's purpose is to end the processing. You would better use an exception for your errors.

来源：https://stackoverflow.com/questions/5577658/spring-batch-how-to-fail-a-job-when-the-itemreader-returns-no-data

标签

Spring

spring-batch