CODEWITHSUNDEEP
annotationsejb
Creature
Creature

Reputation: 141

EJB: what's the point of class-level annotations?

I'm reading this book, Pro JPA2: Mastering the Java Persistance API, and I'm not getting the usefulness of the class-level annotation like in this example:

@EJB(name="cart", beanInterface=ShoppingCart.class)
public class ShoppingCartServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response)
        throws ServletException, IOException {
        HttpSession session = request.getSession(true);
        ShoppingCart cart = (ShoppingCart) session.getAttribute("cart");
        //......
    }
}

What's the point of putting that @EJB if the value of the cart variable won't be auto-injected in there and you have to init the var. yourself? Won't the code work just as well w/o that annotation? What does the annotation actually do?

I get the usefulness of the other type of annotations, like when you put it on the method or a variable, it'll auto-inject stuff. Just here, at the class level, it looks useless.

Upvotes: 3

Views: 1116

Answers (2)

Erhan Bagdemir
Erhan Bagdemir

Reputation: 5327

class level @EJB (or @Resource) defines that your ShoppingCartServlet depends on some EJB, in your case "cart". You need that, if you want to access to EJBs from non-managed context, like POJOs. In this case, you have to make a JNDI look-up in order to get a reference to the EJB which you can define either with ejb-ref (ejb-local-ref) descriptor, or class level @EJB annotation.

Upvotes: 4

Jordan Denison
Jordan Denison

Reputation: 2737

That looks like a class level annotation rather than method level, and I have no idea why one would want to annotate a servlet as EJB, but the @EJB annotation when used properly will provide that class with many different things for free, such as transactions etc...

Upvotes: -1

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