Iterating a map in sightly which have custom object as key

Hi All,

(Similar issue to mine: http://coderissues.com/questions/31437688/how-to-traverse-a-map-having-keys-of-object-type-using-sightly )

I am having tough time iterating a custom map in sightly, previously I have iterated through normal map<String, String> many type in sightly and it worked perfectly fine.

My custom map Map<Product, List<CartEntry>>, As I am using Product as key to my map I have overridden the equals and hashcode method for my product class as below. I am able to iterate the map in normal java class and able to output the required values. But when I trying to iterate it in sightly it is failing and saying error as invalid key.

<div data-sly-list.parentEntry="${shoppingCart.cartItems}" data-sly-unwrap>

         <div data-sly-list.childEntry="${shoppingCart.cartItems[parentEntry]}" data-sly-unwrap>

                 ${childEntry.productCode}

        </div>

</div>

    @Override
    public int hashCode()
    {
        return this.code.hashCode();
    }

    @Override
    public boolean equals(Object obj)
    {
        if (obj == null)
        {
            return false;
        }
        if (getClass() != obj.getClass())
        {
            return false;
        }
        final Product other = (Product) obj;
        if (this.code != other.getCode())
        {
            return false;
        }

        return true;
    }

Not sure how sightly has implemented data-sly-list? So it is possible to iterate this kind of map in sightly?

Any hints would be greatly appreciated, 

Kind regards,

Shehjad