问题
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.
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.
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.
回答1:
You cannot have something like an aggregating processor. Every single item that is read is processed as single item.
However, you can implement a Reader that groups items and forwards them as a whole group. to get an idea, how this could be done have a look at my answer to this question Spring Batch Processor or Dean Clark's answer here Spring Batch-How to process multiple records at the same time in the processor?.
Both use a SpringBatch's SingleItemPeekableItemReader.
来源：https://stackoverflow.com/questions/40389161/aggregating-processor-or-aggregating-reader