[[chunkOrientedProcessing]]
= Chunk-oriented Processing

Spring Batch uses a "`chunk-oriented`" processing style in its most common
implementation. Chunk oriented processing refers to reading the data one at a time and
creating 'chunks' that are written out within a transaction boundary. Once the number of
items read equals the commit interval, the entire chunk is written out by the
`ItemWriter`, and then the transaction is committed. The following image shows the
process:

.Chunk-oriented Processing
image::chunk-oriented-processing.png[Chunk Oriented Processing, scaledwidth="60%"]

The following pseudo code shows the same concepts in a simplified form:

[source, java]
----
List items = new Arraylist();
for(int i = 0; i < commitInterval; i++){
    Object item = itemReader.read();
    if (item != null) {
        items.add(item);
    }
}
itemWriter.write(items);
----

You can also configure a chunk-oriented step with an optional `ItemProcessor`
to process items before passing them to the `ItemWriter`. The following image
shows the process when an `ItemProcessor` is registered in the step:

.Chunk-oriented Processing with Item Processor
image::chunk-oriented-processing-with-item-processor.png[Chunk Oriented Processing With Item Processor, scaledwidth="60%"]

The following pseudo code shows how this is implemented in a simplified form:

[source, java]
----
List items = new Arraylist();
for(int i = 0; i < commitInterval; i++){
    Object item = itemReader.read();
    if (item != null) {
        items.add(item);
    }
}

List processedItems = new Arraylist();
for(Object item: items){
    Object processedItem = itemProcessor.process(item);
    if (processedItem != null) {
        processedItems.add(processedItem);
    }
}

itemWriter.write(processedItems);
----

For more details about item processors and their use cases, see the
xref:processor.adoc[Item processing] section.

