Should the ItemWriter be invoked if the chunk is fully filtered or skipped?

[scordio]

Imagine a step where there is an ItemReader and ItemWriter, without an ItemProcessor:

• The reader returns null immediately
• The writer is never invoked

So far, everything looks good.

Now imagine a step where there is an ItemReader, an ItemProcessor, and an ItemWriter:

• The reader returns only one item, then returns null
• The processor always returns null --> each item is filtered
• The writer is invoked with an empty chunk

Is the writer's invocation with an empty chunk really intended?

The same behavior also occurs in a fault-tolerant step when skipping all items rather than filtering them.

The background of this question is whether custom writer implementations should expect potential empty chunks. If yes, it might be good to emphasize this in the ItemWriter contract.

We detected it in Spring Batch 4.3.10 and confirmed that 6.0.0 shows the same behavior.

[fmbenhassine]

The background of this question is whether custom writer implementations should expect potential empty chunks. If yes, it might be good to emphasize this in the ItemWriter contract.

Yes, and most of item writers provided by Spring Batch check if the chunk is empty before actually writing items. I will turn this into an issue to clarify that detail in the contract of ItemWriter.