Java Shopping Cart Implementation Using Cookies, Redis, and Spring MVC

Introduction: The article discusses four scenarios of a shopping cart based on user login status and browser behavior, using a JD.com template.

Data model: Two JavaBean classes, BuyerCart and BuyerItem , are defined. BuyerCart holds a list of BuyerItem objects and provides methods for adding items, calculating totals, and JSON‑ignore fields. BuyerItem contains a Sku , quantity, and availability flag, with proper equals and hashCode implementations.

Adding items: A JavaScript function addCart() builds a URL with skuId and amount . The Spring MVC controller method buyerCart(...) reads the existing cart from a cookie, creates a new cart if absent, adds the selected SKU, sorts items, and then either stores the cart in Redis (if the user is logged in) or writes it back to a cookie (if not logged in).

JSON conversion: The article shows how to use ObjectMapper with Include.NON_NULL to serialize objects to JSON strings and deserialize them back, demonstrating the process with a test class.

Session handling: A utility RequestUtils.getCSessionId() retrieves or creates a CSESSIONID cookie. SessionProviderService.getAttributterForUsername() fetches the username from Redis and refreshes its expiration.

Persisting the cart: insertBuyerCartToRedis() stores each SKU’s quantity in a Redis hash, merging quantities for duplicate SKUs. selectBuyerCartFromRedis() reconstructs a BuyerCart from the Redis hash.

Cart display: The toCart() controller loads the cart from cookie or Redis, fills each BuyerItem with full Sku details (color, product), and returns the “cart” view.

Checkout validation: The trueBuy() endpoint requires a logged‑in user, extracts the selected SKUs, verifies stock availability, and either returns the cart view with out‑of‑stock flags or proceeds to the order page.