Multi-Line Records Reader (when start prefix = end prefix)

Question

I'm implementing Multi-Line Records Reader solution based on https://docs.spring.io/spring-batch/reference/html/patterns.html#multiLineRecords

I have the following flat file:

HEA;0013100345;2007-02-15
NCU;Smith;Peter;;T;20014539;F
BAD;;Oak Street 31/A;;Small Town;00235;IL;US
HEA;0013100345;2007-02-15
NCU;Smith;Peter;;T;20014539;F
HEA;0013100345;2007-02-15

HEA(and optionally NCU, BAD) must be converted to a single object.
However in my case I don't have "end" line, so "HEA" is a start of new Item and end of previous one at the same time.

Thanks to Dean Clark for the good suggestion below. This is java config of the solution:

@Bean
public FlatFileItemReader<FieldSet> readerFlat() {
    FlatFileItemReader<FieldSet> reader = new FlatFileItemReader<>();
    reader.setResource(new ClassPathResource("multirecord.txt"));
    reader.setLineMapper(compositeLineMapper());
    return reader;
}

@Bean
public SingleItemPeekableItemReader<FieldSet> readerPeek() {
    SingleItemPeekableItemReader<FieldSet> reader = new SingleItemPeekableItemReader<FieldSet>() {{
        setDelegate(readerFlat());
    }};
    return reader;
}

@Bean
public MultiLineCaseItemReader readerMultirecord() {
    MultiLineCaseItemReader multiReader = new MultiLineCaseItemReader() {{
        setDelegate(readerPeek());
    }};
    return multiReader;
}

Then in the custom MultiLineCaseItemReader your can do both read() and peek()

Answer 1

As the reference docs mention, you should create a custom implementation of ItemReader to wrap the FlatFileItemReader.

More specifically, you may want to extend SingleItemPeekableItemReader and use FlatFileItemReader as your delegate.

You'd peek() ahead to the next item. If it's part of your current item, great, go ahead and augment your item. If it's the next "header" line, then you've finished the item you're working and can return the current item.

Then, the next read() will start on the line you just peeked at without losing your place in the file or messing up restartability.