Spring batch和SystemCommandTasklet：不能传递参数

Question

我试图从rest控制器触发一个spring批处理作业，我需要向步骤传递参数。我使用了一个SystemCommandTasklet，正如这里所建议的那样，我将该Tasklet添加为StepListener，但我一直得到一个NPE。

我在这里创建了一个示例项目：如果您运行测试，您将在输出中看到以下内容：

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]

@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;
    }

}

Answer 1

您的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不会将它作为StepExecutionListener代理（这就是为什么它没有注册为监听器，也没有调用BeforeStep方法）。

您需要尽可能明确bean定义方法的返回类型，以便Spring Batch能够正确地代理bean并用正确的类型注册它们。更多详细信息请参见: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禁用生产代码中的作业。您还需要在src/main/resources中添加相同的application.properties。