What if beans that are outjected by Producer changes

[yangju.richard.yang.pearson.com]

For example I have a session scoped producer in my jsf controller bean:
@Named
@SessionScoped

Class Test{
@Inject
    private MyService myService;

@Produces
    @SessionScoped
    @Named
    public List<MyEntity> getEntities() {
        return myService.getEntities();

    }
}

I use producer here to outject List<MyEntity> so that it can be injected into other beans. However, myService.getEntities() returns different list based on user selections. Therefore the myService.getEntities()'s return value changes. My understanding of producer is that it is only call myService.getEntities() once, then the producer will never call myService.getEntities() again.

How do I change the what the producer outjected list? I mean when the end user selects a different parameter in the web page, I need to adjust the getEntities that is outjected?

I guess @Observer won't work in this case, as the myService.getEntities() is only called once no matter what? What if myService.getEntities()return null, will it be called again?

[alesj]

Perhaps change the scope to @RequestScope and do the invalidation logic yourself.

e.g. have backup copy still in session scope, which you return on no-change,
but re-calculate the list on change, and push it back to session scope