spring-batch

Spring Batch

Spring Boot 3.x ships Spring Batch 5. The API changed significantly from 4.x — most online examples are wrong. The two rules that break the most agent-generated code:

1. Do NOT add @EnableBatchProcessing. Boot auto-configures the JobRepository, JobLauncher, and transaction manager. Adding @EnableBatchProcessing disables that auto-configuration and you lose all the wired beans.
2. JobBuilderFactory and StepBuilderFactory are gone. Build jobs and steps with new JobBuilder(name, jobRepository) / new StepBuilder(name, jobRepository), injecting the JobRepository and PlatformTransactionManager Boot already created.

Job & Step (Spring Batch 5 API)

@Configuration
@RequiredArgsConstructor
public class OrderExportJobConfig {

    @Bean
    public Job orderExportJob(JobRepository jobRepository, Step exportStep) {
        return new JobBuilder("orderExportJob", jobRepository)
            .incrementer(new RunIdIncrementer()) // lets the same job be re-run; see "Idempotency"
            .start(exportStep)
            .build();
    }

    @Bean
    public Step exportStep(JobRepository jobRepository,
                           PlatformTransactionManager txManager, // Boot's, injected — do NOT new one up
                           ItemReader<Order> reader,
                           ItemProcessor<Order, OrderRow> processor,
                           ItemWriter<OrderRow> writer) {
        return new StepBuilder("exportStep", jobRepository)
            .<Order, OrderRow>chunk(500, txManager) // chunk size is the commit interval — and a TX boundary
            .reader(reader)
            .processor(processor)
            .writer(writer)
            .faultTolerant()
            .skip(FlatFileParseException.class)
            .skipLimit(50)
            .build();
    }
}

chunk(500, txManager) means: read 500 items, process each, hand the list of 500 to the writer, commit one transaction, repeat. The chunk is the unit of restart and the unit of rollback.