AWS SWF - Workflow passing activity results with signals driving the workflow

I have the requirement to use AWS Simple Workflow (SWF) for an orchestration type of system design. There is parent application that is start this child workflow then signal the workflow to work on activities. I have a workflow that starts up and waits for signals to happen before it can start doing activity work. Once one activity is done then it will report back to by closing out the activity on the parent workflow.

How do I wait for the signal and also use the results from another activity that was invoked by a signal?

Do I need to look into the execution history for the result of an activity and not rely on doing this work in the decide?

Thanks for the help

Code Example:

@SuppressWarnings("unused")
@Slf4j
public class ChildWorkflowImpl implements ChildWorkflow {
    private final Settable<Message> firstStepReceived = new Settable<>();
    private final Settable<Message> secondStepReceived = new Settable<>();


    @Autowired
    private FirstActivityClient firstActivityClient;

    @Autowired
    private SecondActivityClient secondActivityClient;


    @Autowired
    private AmazonSimpleWorkflow amazonSimpleWorkflow;

    @Override
    public void startWorkflow(SubsystemMessage subsystemMessage) {

        //wait for signal to start
        new Task(firstStepReceived) {
            @Override
            protected void doExecute() throws Throwable {
                //Initiate Activity

                startStage(firstStepReceived.get(););
            }
        };

        //wait for second signal but pass in data from first activity
        new Task(secondStepReceived) {
            @Override
            protected void doExecute() throws Throwable {

            }
        };


    }

    public void firstStep(Message message) {
        Promise<FirstActivityResponse> firstActivity = firstActivityClient.execute();

        //wait for signal for disable
        new Task(firstActivity) {
            public void doExecute() {
                //report back status for stage by closing parent activity
            }
        };
    }

    public void secondStep(FirstActivityResponse response) {
        Promise<SecondActivityResponse> secondActivityResponse = secondActivityClient.execute(response);

        new Task(secondActivityResponse) {
            public void doExecute() {
                //report back status for stage
            }
        };

    }
}

You add a signal method to the workflow interface and use Settable to notify the other part of the workflow code about the signal. See Settable documentation from this documentation page.

BTW. I recommend looking at temporal.io which is a greatly improved version of SWF which supports synchronous programming without all these pesky tasks.