On delivery of changeset, how to retrieve component list under a stream via changeset?

Mind your tagging, this is likely "extending" and not administration.

In an SCM delivery advisor like https://rsjazz.wordpress.com/2012/11/01/restrict-delivery-of-changesets-to-workitem-types-advisordelivery-of-changesets-associated-to-wrong-work-item-types-advisor/

The following approaches can be done, as far as I can tell from looking at com.ibm.team.filesystem.service.internal.process.StreamComponentsPermissionAdvisor.class - the class that I found by looking at references of the extension point in said advisor.

Get the components from the destination stream - all components referenced by the stream

		Object operationData = operation.getOperationData();
		if (!(operationData instanceof DeliverOperationData)) {
			return;
		}

		DeliverOperationData data = (DeliverOperationData) operationData;
		IWorkspace destination = data.getDestWorkspace();
		IScmService scmService = this.getScmService();
		IComponentHandle[] componentHandles = scmService
				.getComponentsForWorkspace(destination, null);
		IComponent[] components = (IComponent[]) this
				.getRepositoryItemServiceForScm().fetchItems(componentHandles,
						IRepositoryItemService.COMPLETE);

Get the components from the delivered change sets - not all, but only the ones we deliver to

		Object operationData = operation.getOperationData();
		if (!(operationData instanceof DeliverOperationData)) {
			return;
		}

		DeliverOperationData data = (DeliverOperationData) operationData;
		
		List changeSets = data.getChangeSetHandles();
		IRepositoryItemService itemService = getService(IRepositoryItemService.class);
		IChangeSetHandle[] changeSetHandles = changeSets
				.toArray(new IChangeSetHandle[changeSets.size()]);
		IItem[] items = itemService.fetchItems(changeSetHandles,
				IRepositoryItemService.COMPLETE);
		Collection componentList = new ArrayList();
		HashMap componentHandlesList = new HashMap();
		for (IItem item : items) {
			IChangeSet changeSet = (IChangeSet) item;
			IComponentHandle component = changeSet.getComponent();
			componentList.add(component);
		}