Using both @Stateful and @SessionScoped for shopping cart EJB

Question

I know there's a lot of debate on using stateful vs stateless EJBs in web applications.

The shopping cart is the most common use case: Oracle's Java EE examples use it a lot in the official docs, too.

Here on stackoverflow I found many interesting answers like this The Shopping Cart dilemma in JavaEE which often say something like:

ok... SFSB are good in enterprise, complex scenarios, e.g. if you want to share them with other applications and make them available not only to JSF/web clients

but... if you're just developing your grandpa's e-commerce website, just stick to the HttpSession / SessionScoped cdi-managed bean, and write your business methods in SLSB, as they are more efficient, and so on...

However, because I'm still in a learning and discovery phase, I just want to give SFSB a try, by myself, trying to build a simple shopping cart.

I saw an interesting tutorial suggesting to store a JNDI-retrieved instance of the @Stateful shopping cart ejb interface in the HttpSession, the first time the web client needed it, then use it as usual, during the web session. In my JSF presentation layer, I suppose I would have a @SessionScoped @Named bean (let's call it ShopController), and, in its initialization, store one instance of the stateful ejb in an instance variable.

I wonder if it's possible to directly bind the @Stateful bean to the http session by annotating it with the @SessionScoped CDI annotation.

Will it work as described above? Will CDI create one SFSB for each web session?

Answer 1

@SessionScoped is for @Named beans and @Stateful is for @EJB beans. If I'm not wrong, you cannot annotate 1 bean with both. If you want to use @Stateful, just annotate your ShoppingCart bean with @EJB and @Local and then reference it in your ShopController. Something like this:

@Named
@SessionScoped
public class ShopController {
    ...
    @EJB
    private ShoppingCart cart;
    ...

    // Getters and Setters
}

@Local
@Stateful
public class ShoppingCart {
    ...
}

Answer 2

Don't waste your time learning how to use SFSB for web applications. You will have scalability issues very soon. Why would you learn how to make an application that uses unnecessary server resources?

Even your managed beans shouldn't be SessionScoped. At most create only one very thin SessionScoped MB with small user data to track it and all others should be request, view scoped.

The answer to your question is yes, you can use CDI to bind SessionScoped MB to SFSB EJBs. But this is not a nice architecture for web applications.