outputValueCalc and dfdl:index()

[Sean Muir]

Per an example I came across to have a counter in the output

<xs:element name="counter" type="xs:int" dfdl:outputValueCalc="{../dfdl:index() + 1}" />

This throws an error on the index()

What I am trying to do is have an incremental counter in the output

not sure that this is something I can do with smooks and dfdl

thanks

Sean

[Claude Mamo]

Can you point me to the example? dfdl:index() does not exist in the DFDL spec but there's a dfdl:occursIndex(): https://daffodil.apache.org/docs/dfdl/ . It could be that the function is a vendor extension. This would be a good question for the the Daffodil community.

You can increment a counter from a custom Smooks visitor and insert it from within a pipeline. Here's a naive example I wrote:

    <core:smooks filterSourceOn="#document">
        <core:config>
            <smooks-resource-list>
                <core:rewrite>
                    <resource-config selector="record">
                        <resource>org.smooks.examples.pipeline.MyCounter</resource>
                    </resource-config>
                    <core:echo/>
                </core:rewrite>

                <resource-config selector="record">
                    <resource>org.smooks.examples.pipeline.IncrementCounter</resource>
                </resource-config>
               
                <dfdl:unparser schemaUri="my-schema.dfdl.xsd" unparseOnNode="*"/>
            </smooks-resource-list>
        </core:config>
    </core:smooks>

IncrementCounter maintains a counter in Smooks's bean context:

public class IncrementCounter implements BeforeVisitor {
    @Override
    public void visitBefore(Element element, ExecutionContext executionContext) {
        Integer counter = (Integer) executionContext.getBeanContext().getBean("counter");
        if (counter != null) {
            executionContext.getBeanContext().addBean("counter", counter + 1);
        } else {
            executionContext.getBeanContext().addBean("counter", 1);
        }
    }
}

Whereas MyCounter pulls this counter from the bean context and injects it into the stream:

public class MyCounter implements AfterVisitor {
    @Override
    public void visitAfter(Element element, ExecutionContext executionContext) {
        try {
            Stream.out(executionContext).write(XmlUtils.serialize(element) + String.format("<counter>%s</counter>", executionContext.getBeanContext().getBean("counter")));
        } catch (IOException e) {
            throw new RuntimeException(e);
        }
    }
}

If this a common use case, I reckon we should have an idiomatic way to for inserting counters.

Claude

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[Sean Muir]

We are creating X12 (I am not an expert) and there is a counter feature in one of the segments - I am not sure how prevalent it is in other specs etc 

Thanks for the counter example I will look into using it and will reach out to Daffodil community regarding the index and let you know

Sean

[Claude]

Nice. I had built an X12 translator a few years ago so I think you're referring to the header and trailer segments here. You might want to look into FreeMarker (part of Templating cartridge) for rewriting rather than using a custom visitor such as the one I posted in the example. Soon a blog post about Camel + Smooks + X12 will be published on the Apache Camel blog so keep an eye on it. Here's a link to the repo if you're interested: https://github.com/cjmamo/camel-smooks-edi-x12/ . It demonstrates one way to incrementing counters. I'm posting here the diagram from the draft blog post depicting the flow: