Usage of constructor injection and field injection:

In this case we can probably stick to constructor injection. Besides, java.util.Collection<org.kie.api.runtime.process.WorkItemHandler> handlers; is already available from application.config().processes() so the extra reference is redundant

@org.springframework.stereotype.Component("Travelers")
public class TravelersProcess extends org.kie.kogito.process.impl.AbstractProcess<org.kie.kogito.test.TravelersModel> {

    @org.springframework.beans.factory.annotation.Autowired(required = false)
    java.util.Collection<org.kie.api.runtime.process.WorkItemHandler> handlers;

    org.kie.kogito.app.Application app;

    @org.springframework.beans.factory.annotation.Autowired()
    org.kie.kogito.test.TravelersMessageProducer_7 producer_7;

    public TravelersProcess() {
    }

    @org.springframework.beans.factory.annotation.Autowired()
    public TravelersProcess(org.kie.kogito.app.Application app) {
        super(app.config().process());
        this.app = app;
    }

Usage of PostConstruct

This intialization style makes it harder to create an instance of ProcessInstance without DI – you have to be aware that the annotated method must be invoked.
Besides our initializatoin process is in turn very complicated.

Goal: Streamline this initialization, possibly promote to constructor injection / initialization, and remove all the other methods. Details follow:

• instances are initialized through a call to an activate() via @PostCostruct which means that they cannot be constructed without DI (or without knowing that this method has to be called)

      @javax.annotation.PostConstruct()
      public void init() {
          this.activate();
      }
  
  

• activate() invokes a configure() method; all it does is usually to register the workItemHandler to WorkItemManager – which (1) can be done in some other place (2) it's probably registering the same work item handler multiple times for each process !

    public HotelBookingProcess configure() {
        super.configure();
        handlers.forEach(h -> {
            services.getWorkItemManager().registerWorkItemHandler(h.getName(), h);
        });
        return this;
    }

• the {configure()}

  method default implementation (AbstractProcess) delegates to a third (!!) method registerListeners() that generated code may override; in which case it just registers super.completionEventListener

    protected void registerListeners() {
        services.getSignalManager().addEventListener("flightBooking", completionEventListener);
        services.getSignalManager().addEventListener("hotelBooking", completionEventListener);
    }