TransactionAwareBufferedWriter adds byte order mark on each chunk [BATCH-1985]

Jimmy Praet opened BATCH-1985 and commented

When using a TransactionAwareBufferedWriter (FlatFileItemWriter or StaxEventItemWriter) with an encoding that requires a byte order mark (e.g. UTF-16), the byte order mark (BOM) is emitted on each chunk. On each chunk string.getBytes(encoding) is called on the string buffer, which will return a BOM as the first few bytes of the byte array.

The BOM should only be written at the very beginning of the output stream. If a BOM appears anywhere else, it is interpreted as a 'ZERO-WIDTH NON-BREAKING SPACE'.

http://docs.oracle.com/javase/7/docs/api/java/nio/charset/Charset.html#standard
https://forums.oracle.com/forums/thread.jspa?threadID=2042544
http://www.unicode.org/faq/utf_bom.html

No further details from BATCH-1985

Start by reading TransactionAwareBufferedWriter and its use by FlatFileItemWriter and StaxEventItemWriter, then reproduce the behavior with UTF-16 output written in multiple chunks. Done means the byte order mark appears only at the beginning of the output stream and not on later chunks.