title: Aggregating processor or aggregating reader
body: <p>I have a requirement, which is like, I read items from a DB, if possible in a paging way where the items represent the later "batch size", I do some processing steps, like filtering etc. then I want to accumulate the items to send it to a rest service where I can send it to in batches, e.g. n of them at once instead one by one. </p>
  
  <p>Parallelising it on the step level is what I am doing but I am not sure on how to get the batching to work, do I need to implement a reader that returns a list and a processor that receives a list? If so, I read that you will have not a proper account of number items processed. </p>
  
  <p>I am trying to find a way to do it in the most appropriate spring batch way instead of hacking a fix, I also assume that I need to keep state in the reader and wondered if there is a better way not to.</p>