Spring Batch 当我使用多线程 java.lang.NullPointerException

Question

我在使用 Spring Batch 多线程时遇到错误。错误：无法读取字段“item”，因为“x”为空 当我不使用多线程时，我不会收到任何错误。 我不知道是什么原因导致了这个问题

工作班

@Bean("multiThreadTaskExecutor")
    public SimpleAsyncTaskExecutor getTaskExecutorCreation() {
        SimpleAsyncTaskExecutor executor = new SimpleAsyncTaskExecutor();
        executor.setThreadNamePrefix("Batch-MultiThread");
        return executor;
    }
    
     
    @Autowired
    @Qualifier("multiThreadTaskExecutor")
    private TaskExecutor multiThreadTaskExecutorStepCreation;
    
    public Job createJob(String batchCode, String jobName, int chunkSize, ListItemReader<I> reader, ItemProcessor<O, O> itemProcessor) {
        Step stepCreation = stepBuilderFactory.get(StepName.STEPCREATION.name).listener(new CustomStepExecutionListener(batchCode, batchService)).<I, I>chunk(100).reader(reader)              .writer(createWriter).taskExecutor(multiThreadTaskExecutorStepCreation).throttleLimit(3)
                        .build();
        return jobBuilderFactory.get(jobName).preventRestart()
                        .incrementer(new RunIdIncrementer())
                        .listener(new CustomJobExecutionListener(batchService))
                        .start(stepCreation)
                        .build();
    }
@StepScope
    @Bean(name = "batchExecutionDetailCreateWriter")
    public ItemWriter<I> batchExecutionDetailCreateWriter(@Value("#{stepExecution}") StepExecution stepExecution) {
        List<DetailDto> detailList = new ArrayList<>();
        ItemWriter<I> writer = list -> {
            List<DetailDto> dtoList = new ArrayList<>();
            for (I item : list) {
                DetailDto dto = new DetailDto(batchExecutionId, item, null);
                dtoList.add(dto);
            }
            detailList.addAll(dtoList);
        };   
        return writer;
    }

错误：

2023-11-20 22:59:01.214 TRACE [Payment Batch,,] username=[test]  168594 --- [        Batch-4] o.s.j.c.StatementCreatorUtils            : Setting SQL statement parameter value: column index 5, parameter value [java.lang.NullPointerException: Cannot read field "item" because "x" is null
    at java.base/java.util.LinkedList.unlink(LinkedList.java:215)
    at java.base/java.util.LinkedList.remove(LinkedList.java:530)
    at org.springframework.batch.item.support.ListItemReader.read(ListItemReader.java:52)
    at org.springframework.batch.item.support.ListItemReader$$FastClassBySpringCGLIB$$d4c638f3.invoke(<generated>)
    at org.springframework.cglib.proxy.MethodProxy.invoke(MethodProxy.java:218)
    at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.invokeJoinpoint(CglibAopProxy.java:793)
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:163)
    at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.proceed(CglibAopProxy.java:763)
    at org.springframework.batch.core.step.item.SimpleChunkProvider.provide(SimpleChunkProvider.java:118)
    at org.springframework.batch.core.step.item.ChunkOrientedTasklet.execute(ChunkOrientedTasklet.java:71)
    at org.springframework.batch.core.step.tasklet.TaskletStep$ChunkTransactionCallback.doInTransaction(TaskletStep.java:407)
    at org.springframework.batch.core.step.tasklet.TaskletStep$ChunkTransacti], value class [java.lang.String], SQL type 12

如何解决这个问题？

Answer 1

我建议您检查两件事：

1. 检查ListItemReader读取到的数据不为空。

2. 确保ListItemReader是线程安全的