java - Spring Batch WriterNotOpenException

Question

我创建了一个简单的单步 Spring 批处理作业，它从数据库中读取项目、处理它们并将结果写入 csv。在运行时，我最终得到一个

org.springframework.batch.item.WriterNotOpenException: Writer must be open before it can be written to

相关代码:

@Configuration
@EnableBatchProcessing
@EnableAutoConfiguration
public class CleanEmailJob {

@Autowired
private JobBuilderFactory jobBuilderFactory;

@Autowired
private StepBuilderFactory stepBuilderFactory;

@Autowired
public DataSource dataSource;

@Bean
public ResourcelessTransactionManager transactionManager() {
    return new ResourcelessTransactionManager();
}

@Bean
public MapJobRepositoryFactoryBean mapJobRepositoryFactory(ResourcelessTransactionManager txManager)
        throws Exception {
    MapJobRepositoryFactoryBean factory = new MapJobRepositoryFactoryBean(txManager);
    factory.afterPropertiesSet();
    return factory;
}

@Bean
public JobRepository jobRepository(MapJobRepositoryFactoryBean factory) throws Exception {
    return factory.getObject();
}

@Bean
public JobExplorer jobExplorer(MapJobRepositoryFactoryBean factory) {
    return new SimpleJobExplorer(factory.getJobInstanceDao(), factory.getJobExecutionDao(),
            factory.getStepExecutionDao(), factory.getExecutionContextDao());
}

@Bean
public SimpleJobLauncher jobLauncher(JobRepository jobRepository) {
    SimpleJobLauncher launcher = new SimpleJobLauncher();
    launcher.setJobRepository(jobRepository);
    return launcher;
}


@Bean
public Job cleanEmailAddressesJob() throws Exception {
    return jobBuilderFactory.get("cleanEmailAddresses")
            .incrementer(new RunIdIncrementer())
            .start(processEmailAddresses())
            .build();
}

@Bean
public Step processEmailAddresses() throws UnexpectedInputException, ParseException, Exception {
    return stepBuilderFactory.get("processAffiliates")
            .<AffiliateEmailAddress, VerifiedAffiliateEmailAddress> chunk(10)
            .reader(reader())
            .processor(processor())     
            .writer(report())
            .build();
}

@Bean
public ItemWriter<VerifiedAffiliateEmailAddress> report(){
    FlatFileItemWriter<VerifiedAffiliateEmailAddress> reportWriter = new FlatFileItemWriter<VerifiedAffiliateEmailAddress>();
    reportWriter.setResource(new ClassPathResource("report.csv"));
    DelimitedLineAggregator<VerifiedAffiliateEmailAddress> delLineAgg = new DelimitedLineAggregator<VerifiedAffiliateEmailAddress>();
    delLineAgg.setDelimiter(",");
    BeanWrapperFieldExtractor<VerifiedAffiliateEmailAddress> fieldExtractor = new BeanWrapperFieldExtractor<VerifiedAffiliateEmailAddress>();
    fieldExtractor.setNames(new String[] {"uniekNr", "reason"});
    delLineAgg.setFieldExtractor(fieldExtractor);
    reportWriter.setLineAggregator(delLineAgg);
    reportWriter.setShouldDeleteIfExists(true);
    return reportWriter;
}

如文档中所述，我希望生命周期事件(打开、关闭)能够自动处理，因为我处于单线程和单写入器作业中？

Answer 1

为了详细说明左边的注释，Spring Batch 将在找到任何 ItemStream 实现时自动注册它们，以便在步骤开始时自动打开它们。使用 java config 时，Spring 只知道返回类型是什么。由于您要返回 ItemReader，我们不知道您的实现是否也实现了 ItemStream。使用 java 配置时，我通常建议返回已知的实现(而不是接口(interface))。这允许 Spring 对其进行全面的内省(introspection)。因此，在此示例中，返回 FlatFileItemReader 而不是 ItemReader 将解决问题。