Can I use FlatFileItemWriter to write multi-format file in Spring Batch?

I'm reading a multi-format file using FlatFileItemReader and mapping every line to its corresponding bean type in ItemProcessor and performing data enrichment. But when I try to write these records into a file using FlatFileItemWriter, I'm not able to assign separate BeanWrapperFieldExtractor for the different record types. How can I sort this out?

Input File format

1#9999999#00001#2#RecordType1
2#00002#June#Statement#2020#9#RecordType2
3#7777777#RecordType3

Expected output file format

1#9999999#00001#2#RecordType1#mobilenumber1
2#00002#June#Statement#2020#9#RecordType2#mobilenumber2
3#7777777#RecordType3#mobilenumber3

ItemProcessor

public class RecordTypeItemProcessor implements ItemProcessor<RecordType, RecordType> {

    @Override
    public RecordType process(RecordType recordType) throws Exception {
        if (recordType instanceof RecordType1) {
            RecordType1 recordType1 = (RecordType1) recordType;
            //enrichment logic
            return recordType1;
        } else if (recordType instanceof RecordType2) {
            RecordType2 recordType2 = (RecordType2) recordType;
            //enrichment logic
            return recordType2;
        }
        else
            return null;
    }
}```

You can use a ClassifierCompositeItemProcessor with a ClassifierCompositeItemWriter for that. The idea is to classify items according to their type using a Classifier and call the corresponding item processor/writer. This approach is cleaner IMO than using multiple instance of checks in the processor/writer.

There are some built-in Classifier implementations (I think SubclassClassifier is a good option for you), but you can create your own if needed.

You can find examples in ClassifierCompositeItemProcessorTests and ClassifierCompositeItemWriterTests.