从任务包步骤将参数添加到作业上下文，并在 Spring Batch 的后续步骤中使用

现在，我正在使用 jobParameters 来获取我的 FlatFileItemReader 和 FlatFileItemWriter 的文件名。测试我的批处理是可以的，但我的目标是读取某个目录中的文件（此目录中只有此文件），并且文件名可能会更改。输出文件名应取决于输入文件名。

因此，我想过在我的工作中添加一个新步骤，此步骤将通过搜索良好的目录并在其中查找文件来设置输出和输入文件名。我从Spring Doc中阅读了Transport Data to Future Steps，从SO中阅读了此线程，但我无法使其工作，文件始终为“null”。

首先，我定义了以下任务

public class SettingFilenamesTasklet implements Tasklet {

    private StepExecution stepExecution;

    @Override
    public RepeatStatus execute(StepContribution contribution, ChunkContext chunkContext) throws Exception {
        // TODO Search folder and set real filenames
        String inputFilename = "D:/TestInputFolder/dataFile.csv";
        String outputFilename = "D:/TestOutputFolder/dataFile-processed.csv";
        ExecutionContext stepContext = stepExecution.getExecutionContext();
        stepContext.put("inputFile", inputFilename);
        stepContext.put("outputFile", outputFilename);
        return RepeatStatus.FINISHED;
    }

    @BeforeStep
    public void saveStepExecution(StepExecution stepExec) {
        stepExecution = stepExec;
    }
}

然后，我添加了促销蓖麻豆

@Bean
public ExecutionContextPromotionListener promotionListener() {
    ExecutionContextPromotionListener listener = new ExecutionContextPromotionListener();
    listener.setKeys(new String[]{
            "inputFile", "outputFile"
    });
    return listener;
}

我在我的FlatFileItemWriter定义中通过jobExecutionContext更改了jobParameters（我没有对代码本身进行任何更改）

@Bean
@StepScope
public FlatFileItemWriter<RedevableCRE> flatFileWriter(@Value("#{jobExecutionContext[outputFile]}") String outputFile) {
    FlatFileItemWriter<Employee> flatWriter = new FlatFileItemWriter<Employee>();
    FileSystemResource isr;
    isr = new FileSystemResource(new File(outputFile));
    flatWriter.setResource(isr);
    DelimitedLineAggregator<RedevableCRE> aggregator = new DelimitedLineAggregator<RedevableCRE>();
    aggregator.setDelimiter(";");
    BeanWrapperFieldExtractor<RedevableCRE> beanWrapper = new BeanWrapperFieldExtractor<RedevableCRE>();
    beanWrapper.setNames(new String[]{
        "id", "firstName", "lastName", "phone", "address"
    });
    aggregator.setFieldExtractor(beanWrapper);
    flatWriter.setLineAggregator(aggregator);
    flatWriter.setEncoding("ISO-8859-1");
    return flatWriter;
}

我添加了我的Tasklet豆

@Bean
public SettingFilenamesTasklet settingFilenames() {
    return new SettingFilenamesTasklet();
}

我创建了一个新的步骤来添加到我的工作声明中

@Bean
public Step stepSettings(StepBuilderFactory stepBuilderFactory, SettingFilenamesTasklet tasklet, ExecutionContextPromotionListener listener) {
    return stepBuilderFactory.get("stepSettings").tasklet(tasklet).listener(listener).build();
}

目前，FlatFileItemReader仍然使用jobParameters值，我想让我的FlatFileItemWriter首先工作。我收到以下错误：

[...]    
Caused by: org.springframework.beans.BeanInstantiationException: Failed to instantiate [org.springframework.batch.item.file.FlatFileItemWriter]: Factory method 'flatFileWriter' threw exception; nested exception is java.lang.NullPointerException
    at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:189)
    at org.springframework.beans.factory.support.ConstructorResolver.instantiateUsingFactoryMethod(ConstructorResolver.java:591)
    ... 87 common frames omitted
Caused by: java.lang.NullPointerException: null
    at java.io.File.<init>(Unknown Source)
    at batchTest.BatchConfiguration.flatFileWriter(BatchConfiguration.java:165)
    at batchTest.BatchConfiguration$$EnhancerBySpringCGLIB$$5d415889.CGLIB$flatFileWriter$1(<generated>)
    at batchTest.BatchConfiguration$$EnhancerBySpringCGLIB$$5d415889$$FastClassBySpringCGLIB$$969a8527.invoke(<generated>)
    at org.springframework.cglib.proxy.MethodProxy.invokeSuper(MethodProxy.java:228)
    at org.springframework.context.annotation.ConfigurationClassEnhancer$BeanMethodInterceptor.intercept(ConfigurationClassEnhancer.java:312)
    at batchTest.BatchConfiguration$$EnhancerBySpringCGLIB$$5d415889.flatFileWriter(<generated>)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
    at java.lang.reflect.Method.invoke(Unknown Source)
    at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:162)
    ... 88 common frames omitted

我试图用@JobScope替换@StepScope注释;将我的参数直接放入 jobExecutionContext （+ JobExecutionListener） 中，而不是使用 StepContext + promotionListener...没有任何效果。当我尝试创建 FlatFileItemWriter 时，资源文件始终为空。

我错过了什么？

感谢您的帮助。