如何使用spring Batch为每个列在分隔符前添加空格？

Question

当使用spring Batch从db写入csv文件时，我需要在每个列的分隔符之前根据条件添加空格。

例如，我在csv文件中要求间隔

Column1;Column2;Column3;Column4
AI22;FIENC234DK;EDEJJEDK;JEND4
OR2 ;JFJRN3D   ;DEDERF3E;FEF
EK3R;DJE3DJJEJE;JDJENEJ ;3NEN3

  @Bean
ItemReader<CdVehicle> databaseToCsvItemReader() {
    JdbcCursorItemReader<CdVehicle> databaseReader = new JdbcCursorItemReader<>();

    databaseReader.setDataSource(dataSource);
    databaseReader.setSql(QUERY_FIND_FRIENDS);
    databaseReader.setRowMapper(new BeanPropertyRowMapper<>(CdVehicle.class));

    return databaseReader;
}
@Bean
ItemWriter<CdVehicle> databaseToCsvItemWriter() {
    FlatFileItemWriter<CdVehicle> csvFileWriter = new FlatFileItemWriter<>();

    String exportFileHeader = "CV20VEHID;CV20RFDPR;CV20USAGE;CV20CRVEH;CV20PERID;CV20SITE;CV27PROJ;CV27TYCAI;CV27PHASE;CV27MILLE;CV27CRV;O;CV20DTECL;CV20TEINT;CV20PRINCIPALE;CV20SECONDAIRE;CV20CRBIS;CV36TYPRX";
    StringHeaderWriter headerWriter = new StringHeaderWriter(exportFileHeader);
    csvFileWriter.setHeaderCallback(headerWriter);
    String userhome = System.getProperty("user.home");
    String exportFilePath = userhome + "/tmp/cdv.txt";
    csvFileWriter.setResource(new FileSystemResource(exportFilePath));

    LineAggregator<CdVehicle> lineAggregator = newPersonLineAggregator();
    csvFileWriter.setLineAggregator(lineAggregator);

    return csvFileWriter;
}

@Bean
public Step databaseToCsvStep() {
    return stepBuilderFactory.get("databaseToCsvStep")
            .<CdVehicle, CdVehicle>chunk(100)
            .reader(databaseToCsvItemReader())
            .writer(databaseToCsvItemWriter())
            .build();
}

@Bean
Job databaseToCsvJob() {
    return jobBuilderFactory.get("databaseToCsvJob")
            .incrementer(new RunIdIncrementer())
            .flow(databaseToCsvStep())
            .end()
            .build();
}

private LineAggregator<CdVehicle> newPersonLineAggregator() {
    DelimitedLineAggregator<CdVehicle> lineAggregator = new DelimitedLineAggregator<>();
    lineAggregator.setDelimiter(";");
    FieldExtractor<CdVehicle> fieldExtractor = newPersonFieldExtractor();
    lineAggregator.setFieldExtractor(fieldExtractor);
    return lineAggregator;
}

private FieldExtractor<CdVehicle> newPersonFieldExtractor() {
    BeanWrapperFieldExtractor<CdVehicle> extractor = new BeanWrapperFieldExtractor<>();
    extractor.setNames(new String[] {"CV20VEHID","CV20RFDPR","CV20USAGE","CV20CRVEH","CV20DTAPP","CV20PERID","CV20SITE","CV27PROJ","CV27TYCAI","CV27PHASE","CV27MILLE","CV27CRV","CV27TYMOT","O","CV20DTECL","CV20TEINT","CV20PRINCIPALE", "CV20SECONDAIRE","CV20CRBIS","CV36TYPRX"});
    return extractor;
}

    Column1;Column2;Column3;Column4
    AI22;FIENC234DK;EDEJJEDK;JEND4
    OR2;JFJRN3D;DEDERF3E;FEF
    EK3R;DJE3DJJEJE;JDJENEJ;3NEN3

Answer 1

您可以通过使用Spring批处理FormatterLineAggregator来利用String格式化程序语法。只需将现有的LineAggregator实现替换为以下内容：

java prettyprint-override">private LineAggregator<CdVehicle> newPersonLineAggregator() {
    FormatterLineAggregator<CdVehicle> lineAggregator = new FormatterLineAggregator<>();
    lineAggregator.setFieldExtractor(newPersonFieldExtractor());
    lineAggregator.setFormat("%-4s;%-10s;%-8d;%-5s");
    return lineAggregator;