Ralph, I've seen you post elsewhere that the subscriber client code should be very similar for the server-side code. However, I'm having issues getting it to work. I thought I might try responding here rather than creating a new post on the subject.

For my server-side extension, I've tried getting the working copy and then, for purposes of testing, adding the getAuthenticatedContributor using the getSubscriptions().add method. The participant is super short code-wise.

On the server-side, this doesn't appear to be doing anything. I note that in the client-side code, you don't actually save the work item. I've tried both saving and not saving in my server-side extension, but it didn't matter. I'm not getting exceptions when the participant executes, but nothing changes in the work item. Have you revisited this topic?

Edit: Nevermind. I'm an idiot I guess. I was trying to do this with a JavaScript Attribute Customization before I resorted to doing it via Operation Behavior and forgot to disable the Attribute Customization.

Hi Nate. I assume you have solved the problem in your participant. Anyway, the code below would add a subscriber to a work item based on a user ID. You can use the code in https://rsjazz.wordpress.com/2012/11/30/a-create-approval-work-item-save-participant/ and simply replace the approval creation by the code below. How to save is explained in the link.

    private void createSunscriptionFromUser(IWorkItem workItem, String userID, IProgressMonitor monitor) throws TeamRepositoryException {
        IContributorService contributorService = getService(IContributorService.class);
        IContributorHandle subscriber = contributorService
                .fetchContributorByUserId(userID);
        if (null != subscriber) {
            workItem.getSubscriptions().add(subscriber);
        }
        // Throw some error
    }