Spring批处理和SystemCommandTasklet：无法传递参数

Question

我正在尝试从休息控制器触发弹簧批处理作业，我需要将参数传递给 Step.我使用了 SystemCommandTasklet，并且按照 here 的建议，我将 Tasklet 添加为 StepListener，但我不断收到 NPE。

我创建了一个示例项目here：如果您运行测试，您将在输出中看到：

java.lang.NullPointerException: null
    at org.springframework.batch.core.step.tasklet.SystemCommandTasklet.execute(SystemCommandTasklet.java:133) ~[spring-batch-core-4.2.1.RELEASE.jar:4.2.1.RELEASE]
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:na]
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:na]
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:na]
    at java.base/java.lang.reflect.Method.invoke(Method.java:566) ~[na:na]
    at org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:344) ~[spring-aop-5.2.4.RELEASE.jar:5.2.4.RELEASE]
    at org.springframework.aop.framework.ReflectiveMethodInvocation.invokeJoinpoint(ReflectiveMethodInvocation.java:198) ~[spring-aop-5.2.4.RELEASE.jar:5.2.4.RELEASE]
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:163) ~[spring-aop-5.2.4.RELEASE.jar:5.2.4.RELEASE]
    at org.springframework.aop.support.DelegatingIntroductionInterceptor.doProceed(DelegatingIntroductionInterceptor.java:136) ~[spring-aop-5.2.4.RELEASE.jar:5.2.4.RELEASE]
    at org.springframework.aop.support.DelegatingIntroductionInterceptor.invoke(DelegatingIntroductionInterceptor.java:124) ~[spring-aop-5.2.4.RELEASE.jar:5.2.4.RELEASE]
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186) ~[spring-aop-5.2.4.RELEASE.jar:5.2.4.RELEASE]
    at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:212) ~[spring-aop-5.2.4.RELEASE.jar:5.2.4.RELEASE]
    at com.sun.proxy.$Proxy87.execute(Unknown Source) ~[na:na]
    at org.springframework.batch.core.step.tasklet.TaskletStep$ChunkTransactionCallback.doInTransaction(TaskletStep.java:407) ~[spring-batch-core-4.2.1.RELEASE.jar:4.2.1.RELEASE]
    at org.springframework.batch.core.step.tasklet.TaskletStep$ChunkTransactionCallback.doInTransaction(TaskletStep.java:331) ~[spring-batch-core-4.2.1.RELEASE.jar:4.2.1.RELEASE]
    at org.springframework.transaction.support.TransactionTemplate.execute(TransactionTemplate.java:140) ~[spring-tx-5.2.4.RELEASE.jar:5.2.4.RELEASE]
    at org.springframework.batch.core.step.tasklet.TaskletStep$2.doInChunkContext(TaskletStep.java:273) ~[spring-batch-core-4.2.1.RELEASE.jar:4.2.1.RELEASE]
    at org.springframework.batch.core.scope.context.StepContextRepeatCallback.doInIteration(StepContextRepeatCallback.java:82) ~[spring-batch-core-4.2.1.RELEASE.jar:4.2.1.RELEASE]
    at org.springframework.batch.repeat.support.RepeatTemplate.getNextResult(RepeatTemplate.java:375) ~[spring-batch-infrastructure-4.2.1.RELEASE.jar:4.2.1.RELEASE]
    at org.springframework.batch.repeat.support.RepeatTemplate.executeInternal(RepeatTemplate.java:215) ~[spring-batch-infrastructure-4.2.1.RELEASE.jar:4.2.1.RELEASE]
    at org.springframework.batch.repeat.support.RepeatTemplate.iterate(RepeatTemplate.java:145) ~[spring-batch-infrastructure-4.2.1.RELEASE.jar:4.2.1.RELEASE]
    at org.springframework.batch.core.step.tasklet.TaskletStep.doExecute(TaskletStep.java:258) ~[spring-batch-core-4.2.1.RELEASE.jar:4.2.1.RELEASE]
    at org.springframework.batch.core.step.AbstractStep.execute(AbstractStep.java:208) ~[spring-batch-core-4.2.1.RELEASE.jar:4.2.1.RELEASE]
    at org.springframework.batch.core.job.SimpleStepHandler.handleStep(SimpleStepHandler.java:148) ~[spring-batch-core-4.2.1.RELEASE.jar:4.2.1.RELEASE]
    at org.springframework.batch.core.job.AbstractJob.handleStep(AbstractJob.java:410) ~[spring-batch-core-4.2.1.RELEASE.jar:4.2.1.RELEASE]
    at org.springframework.batch.core.job.SimpleJob.doExecute(SimpleJob.java:136) ~[spring-batch-core-4.2.1.RELEASE.jar:4.2.1.RELEASE]
    at org.springframework.batch.core.job.AbstractJob.execute(AbstractJob.java:319) ~[spring-batch-core-4.2.1.RELEASE.jar:4.2.1.RELEASE]
    at org.springframework.batch.core.launch.support.SimpleJobLauncher$1.run(SimpleJobLauncher.java:147) ~[spring-batch-core-4.2.1.RELEASE.jar:4.2.1.RELEASE]
    at java.base/java.lang.Thread.run(Thread.java:834) ~[na:na]

Tasklet 中的方法beforeStep 永远不会被调用，这会导致 NPE。

这是我的批处理配置：

@Configuration
@EnableBatchProcessing
public class BatchConfiguration extends DefaultBatchConfigurer {

    private final JobBuilderFactory jobBuilderFactory;

    private final StepBuilderFactory stepBuilderFactory;

    public BatchConfiguration(JobBuilderFactory jobBuilderFactory, StepBuilderFactory stepBuilderFactory) {
        this.jobBuilderFactory = jobBuilderFactory;
        this.stepBuilderFactory = stepBuilderFactory;
    }

    @Override
    public JobLauncher getJobLauncher() {
        SimpleJobLauncher jobLauncher = new SimpleJobLauncher();
        jobLauncher.setJobRepository(getJobRepository());
        jobLauncher.setTaskExecutor(new SimpleAsyncTaskExecutor());
        return jobLauncher;
    }

    @Bean
    public Job myJob(Step myStep) {
        return jobBuilderFactory.get("myJob")
                .incrementer(new RunIdIncrementer())
                .start(myStep)
                .build();
    }

    @Bean
    public Step myStep(Tasklet myServiceTasklet) {
        return this.stepBuilderFactory.get("myStep")
                .listener(myServiceTasklet)
                .tasklet(myServiceTasklet)
                .build();
    }

    @Bean
    @StepScope
    public Tasklet myServiceTasklet(
             @Value("#{jobParameters['my_param']}") String param
    ) {
        SystemCommandTasklet tasklet = new SystemCommandTasklet();
        System.out.println(param);
        tasklet.setCommand("sleep 10");
        tasklet.setTimeout(20000);
        return tasklet;
    }

}

我尝试了几十种不同的方法来做到这一点，但我仍然无法弄清楚为什么 Tasklet 中的 beforeStep 方法没有被调用，而字段 execution 仍然是 null

Answer 1

你的tasklet bean定义方法的返回类型应该是SystemCommandTasklet:

@Bean
@StepScope
public SystemCommandTasklet myServiceTasklet(
         @Value("#{jobParameters['my_param']}") String param
) {
    SystemCommandTasklet tasklet = new SystemCommandTasklet();
    System.out.println(param);
    tasklet.setCommand("sleep 10");
    tasklet.setTimeout(20000);
    return tasklet;
}

目前，它返回 Tasklet，因此 Spring Batch 不会将其代理为 StepExecutionListener（这就是它未注册为侦听器且未调用 beforeStep 方法的原因）。

您需要尽可能具体地指定 bean 定义方法的返回类型，以便 Spring Batch 可以正确代理您的 bean 并使用正确的类型注册它们。更多细节在这里：https://stackoverflow.com/a/21941127/5019386。

注意：我下载了您的代码，并注意到您不会像在测试代码中那样在启动时为生产代码禁用作业。您还需要在src/main/resources 中添加相同的application.properties。