title: Get all chunk items before processing?
body: <p>I use <a href="http://projects.spring.io/spring-batch/" rel="nofollow noreferrer">Spring Batch</a> in a project and I'm looking for a way to pre-process all items of a <code>Chunk</code> before the <code>ItemProcessor</code> starts processing. I need to process the items of the chunk together.</p>
  
  <p>There is a <a href="https://docs.spring.io/spring-batch/reference/html/configureStep.html#chunkListener" rel="nofollow noreferrer"><code>ChunkListener</code></a>, which is called only before the <code>ItemReader</code> starts, but not before the <code>ItemProcessor</code> starts. There is also a <a href="http://docs.spring.io/spring-batch/apidocs/org/springframework/batch/core/step/item/ChunkProvider.html" rel="nofollow noreferrer"><code>ChunkProvider</code></a>, which fills the chunk with items. But I found no documentation how to grab the filled chunk.</p>
  
  <p>How can I access all items of <code>Chunk</code> after the <a href="https://docs.spring.io/spring-batch/reference/html/configureStep.html#chunkOrientedProcessing" rel="nofollow noreferrer">step</a> finished reading?</p>