7.2. Transforming items

Transforming read items and then writing them out is the typical use case for an item processor. In Spring Batch, we distinguish two kinds of transformation: changing the state of the read item, and producing a new object based on the read item. In the latter case, the object the processor returns can be of a different type than the incoming item.

We illustrate both kinds of transformation with our online store application. Imagine that the application is successful and that other companies ask ACME to add their products to the online catalog; for this service, ACME takes a percentage of each partner’s product sold. For the application, this means importing products from different files: a file for its own catalog and a file for each partner catalog. With this use case in mind, let’s first explore transforming the state of read items.