在为每个孩子添加Bean后，请添加这部分代码，如果有问题请发送错误消息到这里。

public class CommonDTOItemWriter implements ItemWriter<CommonDTO> {

    @Autowired
    private FlatFileItemWriter<ParentDTO> parentWriter;

    @Autowired
    private FlatFileItemWriter<Child1DTO> child1Writer;

    @Autowired
    private FlatFileItemWriter<Child2DTO> child2Writer;

    @Override
    public void write(List<? extends CommonDTO> items) throws Exception {
        for (CommonDTO item : items) {
            // Write parentDTO to parent.dat
            parentWriter.write(Arrays.asList(item.getParentDTO()));

            
            child1Writer.write(item.getChild1DTOList());

            
            child2Writer.write(item.getChild2DTOList());
        }
    }
}

如果您遗漏了以下内容，请添加此部分：

public class Child1DTOItemWriter extends FlatFileItemWriter<Child1DTO> {

    @Value("${output.file.path}")
    private String outputPath;

    private String filename;

    @BeforeStep
    public void beforeStep(StepExecution stepExecution) {
        filename = outputPath + "child1DTO_" + stepExecution.getStepName() + ".dat";
        this.setResource(new FileSystemResource(filename));
        this.setAppendAllowed(true);
        this.setHeaderCallback(writer -> writer.write("Header line"));
        this.setFooterCallback(writer -> writer.write("Footer line"));
        this.setLineAggregator(new PassThroughLineAggregator<>());
        this.open(stepExecution.getExecutionContext());
    }

    @Override
    public void write(List<? extends Child1DTO> items) throws Exception {
       
        super.write(items);
    }
}

在属性文件中添加：

output.file.path=output/

@Bean
@StepScope
public FlatFileItemWriter<ParentDTO> parentDTOFlatFileItemWriter(@Value("#{stepExecutionContext['output.file.path']}") String filePath) {
    return new FlatFileItemWriterBuilder<ParentDTO>()
            .name("parentDTOFlatFileItemWriter")
            .resource(new FileSystemResource(filePath + "/parentDTO.dat"))
            .delimited()
            .delimiter(",")
            .names("parentField1", "parentField2", "parentField3") // replace with your actual field names
            .build();
}

@Bean
@StepScope
public FlatFileItemWriter<List<Child1DTO>> child1DTOFlatFileItemWriter(@Value("#{stepExecutionContext['output.file.path']}") String filePath) {
    return new FlatFileItemWriterBuilder<List<Child1DTO>>()
            .name("child1DTOFlatFileItemWriter")
            .resource(new FileSystemResource(filePath + "/child1DTO.dat"))
            .delimited()
            .delimiter(",")
            .names("child1Field1", "child1Field2", "child1Field3") // replace with your actual field names
            .build();
}

@Bean
@StepScope
public FlatFileItemWriter<List<Child2DTO>> child2DTOFlatFileItemWriter(@Value("#{stepExecutionContext['output.file.path']}") String filePath) {
    return new FlatFileItemWriterBuilder<List<Child2DTO>>()
            .name("child2DTOFlatFileItemWriter")
            .resource(new FileSystemResource(filePath + "/child2DTO.dat"))
            .delimited()
            .delimiter(",")
            .names("child2Field1", "child2Field2", "child2Field3") // replace with your actual field names
            .build();
}

应该为不同的文件编写不同的Bean。
例如：

@Bean
public FlatFileItemWriter<Child1DTO> child1Writer() {
    FlatFileItemWriter<Child1DTO> writer = new FlatFileItemWriter<>();
    writer.setResource(new FileSystemResource("child1.dat"));
    writer.setLineAggregator(new PassThroughLineAggregator<>());
    return writer;
}