import io.micronaut.http.annotation.Get
import io.micronaut.http.annotation.Post
import io.micronaut.session.Session
import io.micronaut.session.annotation.SessionValue
import javax.annotation.Nullable
import javax.validation.constraints.NotBlank
@Controller("/shopping")
class ShoppingController {
    Cart addItem(Session session, @NotBlank String name) { (2)
        Cart cart = session.get(ATTR_CART, Cart.class).orElseGet({ ->  (3)
            Cart newCart = new Cart()
            session.put(ATTR_CART, newCart) (4)
            newCart
        })
        cart.getItems().add(name)
        cart
    }
}

Note that because the is declared as a required parameter to the execute the controller action, the Session will be created and saved to the .

Using @Nullable with Sessions

    @Post("/cart/clear")
    void clearCart(@Nullable Session session) {
        if (session != null) {
            session.remove(ATTR_CART);
        }
    }

Using @Nullable with Sessions

    @Post("/cart/clear")
    internal fun clearCart(session: Session?) {
        session?.remove(ATTR_CART)