LineCallbackHandlers being aware of which Resource they are handling lines for

[tomgeraghty3]

My issue is explained in detail in Stackoverflow here

Expected Behavior
I use a LineCallbackHandler to skip header lines in my file. I need to know which file resource the handler is currently skipping lines for. This used to be able to be achieved through MultiResourceItemReader.getCurrentResource() but this directly couples the MultiResourceItemReader to the LineCallbackHandler and recently that method has been deprecated.

Current Behavior
As suggested by @fmbenhassine in the Stackoverflow question there is a way to get this information by directly coupling the FlatFileItemReader itself to the LineCallbackHandler but this is just a workaround that essentially replicates the coupling in a different place.

As confirmed by @fmbenhassine Spring Batch offers no out of the box way to implement what I am trying to achieve without coupling.
An approach suggested by @fmbenhassine is to create a new interface ResourceAwareLineCallbackHandler that the FlatFileItemReader can make use of.
As also suggested by @fmbenhassine there may be other use cases for what I am trying to achieve such as lines considered as comment and knowing the source file of each comment line

This feature request is to discuss different options for implementing desired behaviour.

[fmbenhassine]

Thank you for raising this feature request as discussed in SO.

In hindsight, we probably don't need a new interface for that use case, since the line callback handler could be made aware of the current resource by making it implement the, currently available, ResourceAware interface, something like:

import org.springframework.batch.item.ResourceAware;
import org.springframework.core.io.Resource;

public class MyResourceAwareLineCallbackHandler implements LineCallbackHandler, ResourceAware {

	private Resource resource;
	
	@Override
	public void setResource(Resource resource) {
		this.resource = resource;
	}

	@Override
	public void handleLine(String line) {
		System.out.println("Skipping line " + line + " from resource " + resource.getFilename());
	}
}

I think using polymorphism with the currently available interfaces is better than introducing a new interface. What do you think?