Spring Boot + Batch：在 ItemReader 中注入/自动装配的 bean 为空

Question

当我尝试自动装配 ItemReader 中的任何 bean 时，我得到了一个 NPE。有人可以帮我解决我出错的地方吗？谢谢！

要求是我想在 ItemReader 中注入一个 DAO 以从多个源获取数据并创建一个对象。

这是我拥有的配置类 -

    @Configuration
@EnableBatchProcessing
@EnableScheduling
@EnableAutoConfiguration(exclude = { DataSourceAutoConfiguration.class })
public class ReportMetadataConfig {

    @Autowired
    private JobBuilderFactory jobBuilderFactory;

    @Autowired
    private StepBuilderFactory stepBuilderFactory;

    @Autowired
    private JobLauncher jobLauncher;

    @Autowired
    private Job fetchReportMetadataJob;

    @Bean
    public Job fetchReportMetadataJob() {
        return jobBuilderFactory.get("fetchReportMetadataJob")
                .incrementer(new RunIdIncrementer()).listener(listener())
                .flow(reportWriterStep()).end().build();
    }

    @Bean
    public Step reportWriterStep() {
        return stepBuilderFactory.get("reportWriterStep").<ReportMetadataDTO, ReportMetadataDTO> chunk(1)
                .reader(compositeItemReader())
                .processor(new ReportMetadataProcessor())
                .writer(reportMetadataWriter()).build();
    }

    public ItemReader<ReportMetadataDTO> compositeItemReader() {
        return new CompositeItemReader();
    }

    public ItemWriter<ReportMetadataDTO> reportMetadataWriter() {
        return new ReportMetadataWriter();
    }

    @Bean
    public JobExecutionListener listener() {
        return new ReportMetadataCompletionListener();
    }

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


}

这是我创建的复合 ItemReader -

    @Component
public class CompositeItemReader implements ItemReader<ReportMetadataDTO> {

    private ItemReader<String> recordReader;

    @Autowired
    private ReportMetadataService reportMetadataService;

    @Override
    public ReportMetadataDTO read() throws Exception, UnexpectedInputException, ParseException,
            NonTransientResourceException {

        reportMetadataService.getReportMetada();
        /*if(recordReader == null) {
            recordReader = new IteratorItemReader<String>(getRecords());
        }*/
        ReportMetadataDTO data = new ReportMetadataDTO();
        //return recordReader.read();
        return data;
    }

}

这是我想调用的服务，它在 ItemReader 中自动装配。

    @Service
public class ReportMetadataServiceImpl implements ReportMetadataService {

    @Autowired
    private ReportMetadataDao reportMetadataDao;

    @Override
    public void getReportMetada() {
        reportMetadataDao.getReportDetails();
    }

}

编辑 -

堆栈跟踪 -

java.lang.NullPointerException: null
    at com.test.batch.jobs.ReportMetadata.step.CompositeItemReader.read(CompositeItemReader.java:40)
    at com.test.batch.jobs.ReportMetadata.step.CompositeItemReader.read(CompositeItemReader.java:1)
    at org.springframework.batch.core.step.item.SimpleChunkProvider.doRead(SimpleChunkProvider.java:91)
    at org.springframework.batch.core.step.item.SimpleChunkProvider.read(SimpleChunkProvider.java:157)
    at org.springframework.batch.core.step.item.SimpleChunkProvider$1.doInIteration(SimpleChunkProvider.java:116)
    at org.springframework.batch.repeat.support.RepeatTemplate.getNextResult(RepeatTemplate.java:374)
    at org.springframework.batch.repeat.support.RepeatTemplate.executeInternal(RepeatTemplate.java:215)
    at org.springframework.batch.repeat.support.RepeatTemplate.iterate(RepeatTemplate.java:144)
    at org.springframework.batch.core.step.item.SimpleChunkProvider.provide(SimpleChunkProvider.java:110)
    at org.springframework.batch.core.step.item.ChunkOrientedTasklet.execute(ChunkOrientedTasklet.java:69)
    at org.springframework.batch.core.step.tasklet.TaskletStep$ChunkTransactionCallback.doInTransaction(TaskletStep.java:406)
    at org.springframework.batch.core.step.tasklet.TaskletStep$ChunkTransactionCallback.doInTransaction(TaskletStep.java:330)
    at org.springframework.transaction.support.TransactionTemplate.execute(TransactionTemplate.java:133)
    at org.springframework.batch.core.step.tasklet.TaskletStep$2.doInChunkContext(TaskletStep.java:271)
    at org.springframework.batch.core.scope.context.StepContextRepeatCallback.doInIteration(StepContextRepeatCallback.java:81)
    at org.springframework.batch.repeat.support.RepeatTemplate.getNextResult(RepeatTemplate.java:374)
    at org.springframework.batch.repeat.support.RepeatTemplate.executeInternal(RepeatTemplate.java:215)
    at org.springframework.batch.repeat.support.RepeatTemplate.iterate(RepeatTemplate.java:144)
    at org.springframework.batch.core.step.tasklet.TaskletStep.doExecute(TaskletStep.java:257)
    at org.springframework.batch.core.step.AbstractStep.execute(AbstractStep.java:200)
    at org.springframework.batch.core.job.SimpleStepHandler.handleStep(SimpleStepHandler.java:148)
    at org.springframework.batch.core.job.flow.JobFlowExecutor.executeStep(JobFlowExecutor.java:64)
    at org.springframework.batch.core.job.flow.support.state.StepState.handle(StepState.java:67)
    at org.springframework.batch.core.job.flow.support.SimpleFlow.resume(SimpleFlow.java:169)
    at org.springframework.batch.core.job.flow.support.SimpleFlow.start(SimpleFlow.java:144)
    at org.springframework.batch.core.job.flow.FlowJob.doExecute(FlowJob.java:134)
    at org.springframework.batch.core.job.AbstractJob.execute(AbstractJob.java:306)
    at org.springframework.batch.core.launch.support.SimpleJobLauncher$1.run(SimpleJobLauncher.java:135)
    at org.springframework.core.task.SyncTaskExecutor.execute(SyncTaskExecutor.java:50)
    at org.springframework.batch.core.launch.support.SimpleJobLauncher.run(SimpleJobLauncher.java:128)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:333)
    at org.springframework.aop.framework.ReflectiveMethodInvocation.invokeJoinpoint(ReflectiveMethodInvocation.java:190)
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:157)
    at org.springframework.batch.core.configuration.annotation.SimpleBatchConfiguration$PassthruAdvice.invoke(SimpleBatchConfiguration.java:127)
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
    at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:213)
    at com.sun.proxy.$Proxy74.run(Unknown Source)
    at org.springframework.boot.autoconfigure.batch.JobLauncherCommandLineRunner.execute(JobLauncherCommandLineRunner.java:214)
    at org.springframework.boot.autoconfigure.batch.JobLauncherCommandLineRunner.executeLocalJobs(JobLauncherCommandLineRunner.java:231)
    at org.springframework.boot.autoconfigure.batch.JobLauncherCommandLineRunner.launchJobFromProperties(JobLauncherCommandLineRunner.java:123)
    at org.springframework.boot.autoconfigure.batch.JobLauncherCommandLineRunner.run(JobLauncherCommandLineRunner.java:117)
    at org.springframework.boot.SpringApplication.callRunner(SpringApplication.java:776)
    at org.springframework.boot.SpringApplication.callRunners(SpringApplication.java:760)
    at org.springframework.boot.SpringApplication.afterRefresh(SpringApplication.java:747)
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:315)
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1162)
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1151)
    at com.test.CustomReportWriterApplication.main(CustomReportWriterApplication.java:12)

Answer 1

您没有正确连接 bean。您想要@Component在您的类上使用并让 Spring 创建它，或者添加@Bean工厂方法并由您创建它。在这种情况下，您将@Component获得 Spring 知道的一个实例，但这不是您要注入到ItemReader. 您注入的内容ItemReader是一个普通的内容，不是自动装配的（因为 Spring 不知道这一点）。我建议@Component从您的中删除CompositeItemReader并添加@Bean到public ItemReader<ReportMetadataDTO> compositeItemReader().