Clarification needed with Spring batch concepts

Question

I am new at Spring batch and I am having an issue implementing my business use case with Spring batch.

Basically, I am reading data from a database i.e. a List of subscribers to a newsletter. I then need to send an email to each subscriber as well as to insert data into the database in order to know which subscriber the email was sent to.

I use an ItemProcessor implementation whose process method returns a MimeMessage and takes a subscriber as an argument; the writer associated with this processor is of type: org.springframework.batch.item.mail.javamail.MimeMessageItemWriter.

The issue is that I need another writer for the database inserts (possibly using a CompositeItemWriter) that takes a List of subscribers as an argument and all I have as input is a MimeMessage from the above ItemProcessor.

Can anyone please help?

Answer 1

From what you've said using the ItemProcessor interface to save the message to the database is conceptually not right. You need to use ItemWriter for that. You can implement writing to DB as ItemWriter and sending the mail message as ItemWriter and use CompositeItemWriter to combine them.

• Subscriber is passed to these item writers.
• The transformation of Subscriber to MimeMessage is done by 2nd writer internally before transferring to MimeMessageItemWriter (which is aggregated by this writer).
• Sending the message to subscriber should be done after saving to the DB, as DB can be rolled back if something goes wrong with sending the message (if you need that functionality), and your batch size should be 1 (otherwise rollback will wrongly discard all notifications which have been successfully sent).