从tasklet步骤向作业上下文添加参数，并在Spring批处理的后续步骤中使用

Question

目前，我使用jobParameters获取FlatFileItemReader和FlatFileItemWriter的文件名。测试我的批处理是可以的，但是我的目标是读取某个目录中的文件（这个目录中只有这个文件），并且文件名可能会更改。输出文件名应该依赖于输入文件名。

因此，我考虑在我的工作中添加一个新的步骤，这个步骤将通过搜索好的目录并向其中查找文件来设置输出和输入文件名。我从Spring Doc读到向未来步骤传递数据，并且从SO读到这个线程，但是我不能使它工作，文件总是“空”。

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promotionListener bean

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

我通过FlatFileItemWriter定义中的jobExecutionContext更改了jobParameters（我没有更改代码本身的一行）

@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;
}

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

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

[...]    
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

我错过了什么？

谢谢你的帮助。

Answer 1

在tasklet中，您可以使用chunkcontext，因此您不需要@beforesteep，您可以删除它（在我的配置中，它根本没有被调用，并且当您将它视为一个动作时，步骤没有多大意义，但我没有看到NPE，所以猜测该部分工作）。我们用两种方法之一解决了这个问题：

>

您可以直接使用chunkcontext.getstepcontext().getstepexecution().getjobexecution().getexecutioncontext().put（“inputfile”,inputFilename）；将tasklet中的任何参数放入作业executioncontext

您可以将ExecutionContextPromotionListener添加到任务步骤中，然后执行ChunkContext.GetStepContext().GetStepExecution().GetExecutionContext().Put（“InputFile”,inputFilename）；