Relationships: Order – Item – Payment

Problem

Model an e-commerce Order to understand the three types of object relationships: Composition (Order owns LineItems — items cannot exist without the order), Aggregation (Order references a Customer — customer exists independently), and Association (Order uses a Payment — payment can outlive the order).

Requirements

▸Order COMPOSES LineItems — LineItem has no meaning outside an Order
▸Order AGGREGATES a Customer — Customer exists independently
▸Order ASSOCIATES with Payment — Payment is separate, can reference multiple orders
▸Order.addItem(product, qty) — adds LineItem internally
▸Order.calculateTotal() — sums all LineItem prices
▸Order.placeOrder(payment) — validates and creates a payment record
▸Customer.getOrderHistory() — returns all orders for this customer

Constraints

–LineItem cannot be created outside Order context (make constructor package-private or use factory on Order)
–Deleting an Order should also delete its LineItems (cascade)
–Deleting an Order should NOT delete the Customer or Payment

✓ Saved