Call an RFC as a Workflow step

Hi,

I need to integrate inside a workflow (designed via Process Composer) a call to a backend RFC.

In detail, I need to make a callback to the backend when a process is created to register the successful creation of the process itself.

So it should be something like this:

START --> AUTOMATED RFC CALLBACK --> Workflow tasks --> END

I'm trying adding an EJB and linking it to the workflow with a Mapping Activity, but I'm not sure that I'm doing the right thing.

I've found a SAP guide that shows how to call an EJB from a workflow with a Mapping Activity but I'm having problems making things work.

Can someone suggest me if this is the right way to get the things done?

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As a side note:

I work in a multi-track development environment. Every track has inside a project representing a specific workflow. Could it be possible to have a single EJB, placed in a track, to handle all the callback request from all the workflows from different tracks?

Thank you,

Pietro