如何将会话对象放入哈希图中

Question

I am saving a HashMap into a session like so:

HashMap<Integer, Cart> cart = new HashMap<>();
            cart.put(id, new Cart(product.getName(), product.getPrice(), 1, product.getImage()));
            session.setAttribute("cart", cart);

But how am I supposed to get it out of the session back into a HashMap ?

I am aware that the session data is stored as an object but do not know how to get it into a HashMap

I've tried:

HashMap<Integer, Cart> cart = session.getAttribute("cart");

But it says cannot from Object to HashMap

Answer 1

getAttribute returns Object

public Object getAttribute(String name)

You can cast Map as,

HashMap<Integer, Cart> cart = (HashMap<Integer, Cart>) session.getAttribute("cart");

Answer 2

session stores the values as Object. You need to type cast when retrieving from session to the type of object you stored in session.