Question

In ASP.net, I have the following code. I’m making a website in JSP and using Java classes. Basically I want to incorporate the same functionality of this constructor.

What is Java code for the following c# code?

public class ShoppingCart
{
    #region ListCart

    public List<CartItem> Items { get; private set; }

    #endregion

    #region CartSession


    public static readonly ShoppingCart Instance;

    static ShoppingCart()
    {

        if (HttpContext.Current.Session["ASPNETShoppingCart"] == null)
        {
            Instance = new ShoppingCart();
            Instance.Items = new List<CartItem>();
            HttpContext.Current.Session["ASPNETShoppingCart"] = Instance;
        }
        else
        {
            Instance = (ShoppingCart)HttpContext.Current.Session["ASPNETShoppingCart"];
        }
    }
}

Answer 1

In Java, you will have to play with HttpServletRequest or HttpSession (which is most preferred) since you’re storing a ShoppingCart into a session.

I would not create a ShoppingCart class to store instance of it in a Session, since ShoppingCart can exists outside of Web context. A Simple way to do what you requested is to create a utility class to store / retrieve a shopping cart in/from the session.

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpSession;

public class ShoppingCartUtil {

    public static ShoppingCart getShoppingCart(HttpServletRequest request, String sessionName) {
        return getShoppingCart(request.getSession(), sessionName);
    }

    public static ShoppingCart getShoppingCart(HttpSession session, String sessionName) {
        return (ShoppingCart)session.getAttribute(sessionName);
    }

    public static void addShoppingCartToSession(HttpServletRequest request, String sessionName, ShoppingCart cart) {
        addShoppingCartToSession(request.getSession(), sessionName, cart);
    }

    public static void addShoppingCartToSession(HttpSession session, String sessionName, ShoppingCart cart) {
        session.removeAttribute(sessionName);
        session.setAttribute(sessionName, cart);
    }
}