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  • Writing many lines from one item in FlatFileItemReader

    I am using the FlatFileItemWriter to write data read by a reader. Each read item results in writing N lines in the file.
    What is the strategy to be used in this case ?

    My first idea is to set up a ItemTransformer that transforms the item into a List of N sub-items. The list is passed as a single item to the FlatFileItemWriter.write() method; a FieldSetCreator creates a huge FieldSet containing N*nb_fields_per_sub_item fields, and a LineAggregator creates a String containing N lines (i.e. the returned String contains \n characters), with a double nested loop: (for i=0..N) and for (j=0..nb_fields_per_sub_item).
    There is however a problem with this : the FlatFileItemReader increments its the linesWritten counter by one for each written line, even if the line contains \n characters.

    I really need to the know the exact number of written lines, as each line of the output file must start with the line number.
    Last edited by gpitteloud; Sep 12th, 2008, 07:07 AM.

  • #2
    Couldn't you just call write multiple times?

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    • #3
      In order to call write() multiple times, I would need to write my own ItemWriter that delegates to the FlatFileItemWriter and invokes the FFIW write() method multiple times in my write() method. While this sounds possible, I was wondering if a solution exists, that allows me to use the FFIW as is (without the need to write my own ItemWriter wrapping it) and just configure it with a special FieldSetCreator and LineAggregator that would do the work.

      So, do you think writing my own ItemWriter wrapping a FFIW is a better way to go than using the FFIW as is and configure it with home-made FieldSetCreator and LineAggregator components ?

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      • #4
        I would wrap the FFIW, the other approach is much more complex I think, and I don't see any problem with the composite writer.

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