Question

我正在使用Spring Batch来读取CSV文件，对其进行处理并在进行一些处理后将其写回。当源与目标之间存在一对一的关系时，这很简单，但是根据我的业务逻辑是，在某些情况下，输入中的一行会在输出文件中产生多于一行。

这是处理器的外观，但我找不到有关如何为其编写Writer的任何信息。

public class CsvRowsProcessor implements ItemProcessor<RowInput, List<RowOutput>>{

    @Override
    public List<RowOutput> process(final RowInput rowInput)  {

        final String id = rowInput.getId();
        final String title = rowInput.getTitle();
        final String description = rowInput.getDescription();
        final RowOutput transformedRowInput = new RowOutput(id, title, description);

        List<RowOutput> rows=new LinkedList<>();
        rows.add(transformedRowInput);
        return rows;
    }

}

有关如何处理此问题的任何想法？

当前作家：

@Bean
ItemWriter<RowOutput> csvRowsWriter() {
    FlatFileItemWriter<RowOutput> csvFileWriter = new FlatFileItemWriter<>();
    csvFileWriter.setResource(new FileSystemResource("C:\\Users\\orenl\\IdeaProjects\\Spring-Batch-CSV-Example\\src\\main\\resources\\outputFile.csv"));
    LineAggregator<RowOutput> lineAggregator = createLineAggregator();
    csvFileWriter.setLineAggregator(lineAggregator);
    csvFileWriter.setHeaderCallback(new FlatFileHeaderCallback() {

        public void writeHeader(Writer writer) throws IOException {
            writer.write("Id,Title,Description");
        }
    });
    return csvFileWriter;
}



private LineAggregator<RowOutput> createLineAggregator() {
    DelimitedLineAggregator<RowOutput> lineAggregator = new DelimitedLineAggregator<>();
    lineAggregator.setDelimiter(",");

    FieldExtractor<RowOutput> fieldExtractor = createFieldExtractor();
    lineAggregator.setFieldExtractor(fieldExtractor);

    return lineAggregator;
}

private FieldExtractor<RowOutput> createFieldExtractor() {
    BeanWrapperFieldExtractor<RowOutput> extractor = new BeanWrapperFieldExtractor<>();
    extractor.setNames(new String[] { "Id", "Title", "Description" });
    return extractor;
}

@Bean
public Step csvFileToFileStep() {
    return stepBuilderFactory.get("csvFileToFileStep")
            .<RowInput ,RowOutput>chunk(1)
            .reader(csvRowsReader())
            .processor(csvRowsProcessor())
            .writer(csvRowsWriter())
            .build();
}

@Bean
Job csvFileToCsvJob(JobCompletionNotificationListener listener) {
    return jobBuilderFactory.get("csvFileToCsvJob")
            .incrementer(new RunIdIncrementer())
            .listener(listener)
            .flow(csvFileToFileStep())
            .end()
            .build();
}

寻找一种解决方案，使我可以使用setLineAggregator（lineAggregator）;但不会将所有行写为一行。

Answer 1

您需要定义一个接受列表列表的编写器：

class MyItemWriter implements ItemWriter<List<RowOutput>> {
    public void write(List<? extends List<RowOutput>> items) {
         // write items here
    }    
}

可以在这里找到类似的问题：Using an ItemWriter with List of Lists。

希望这会有所帮助。

如何使用Spring Batch读取CSV，对其进行处理并以CSV格式写成一行而产生多行？

1 个答案: