嘿,新晉建築師們! ?♂️? ♀️ 準備好深入了解底層設計的本質了嗎?可以這樣想:底層設計是軟體大樓每個細節的神奇藍圖!沒有它,你就會陷入混亂,就像在浴室裡放了一台冰箱一樣。讓我們來解決這個問題!
低階設計 (LLD) 專注於系統的精細細節。如果高級設計 (HLD) 是您的地圖,顯示城市和高速公路,那麼 LLD 就是 GPS 放大以顯示您要轉向哪條街道才能到達目的地。這是功能性和精緻性的完美結合!這是關於定義:
現在想像一下建立一個像食品配送應用程式這樣的專案。 LLD 回答如何您的系統將處理特定任務。從哪些類別負責餐廳數據,到如何建立 API 呼叫以顯示使用者的訂單歷史記錄。
場景:我們正在為 Zomato 或 Uber Eats 等線上食品配送服務設計一個低階系統。目標:順利處理訂單、用戶、餐廳和送貨,而無需創建意大利麵條代碼? .
在這個級別,你是導演。你需要挑選完美的「演員」(班級)並告訴他們要扮演什麼角色。
java Copy code class User { private String userId; private String name; private String email; private List<Order> orders; public User(String userId, String name, String email) { this.userId = userId; this.name = name; this.email = email; this.orders = new ArrayList<>(); } public void placeOrder(Order order) { orders.add(order); } // Getters and Setters } class Restaurant { private String restaurantId; private String name; private List<FoodItem> menu; public Restaurant(String restaurantId, String name, List<FoodItem> menu) { this.restaurantId = restaurantId; this.name = name; this.menu = menu; } public List<FoodItem> getMenu() { return menu; } } class Order { private String orderId; private User user; private Restaurant restaurant; private List<FoodItem> foodItems; private OrderStatus status; public Order(String orderId, User user, Restaurant restaurant, List<FoodItem> foodItems) { this.orderId = orderId; this.user = user; this.restaurant = restaurant; this.foodItems = foodItems; this.status = OrderStatus.PENDING; } public void updateOrderStatus(OrderStatus status) { this.status = status; } }
為什麼是類別? 將它們視為樂高積木? 。沒有它們,你就會得到一大堆無結構的磚塊。我們定義誰(使用者、餐廳)和什麼(訂單)參與。
現在您已經有了“演員”,讓我們看看他們如何互動。沒有對白的戲劇算什麼,對吧?
當使用者下訂單時,它會建立訂單的新實例。但是,如果用戶仍在考慮要買哪個披薩怎麼辦?在這裡,OrderStatus 可以幫助我們追蹤訂單是否為 待定、進行中 或 已交付。
餐廳有菜單(廢話!),其中包含食物清單。當用戶下訂單時,他們會從這些商品中進行選擇。
java Copy code class FoodItem { private String itemId; private String name; private double price; public FoodItem(String itemId, String name, double price) { this.itemId = itemId; this.name = name; this.price = price; } }
以下是送餐應用中的典型事件流程:
序列圖可以幫助您視覺化物件如何跨時間互動。它逐步向您展示用戶、訂單、餐廳和送貨合作夥伴如何結合在一起。
sql Copy code +---------+ +------------+ +--------------+ +--------------+ | User | | Restaurant | | Delivery | | Order | +---------+ +------------+ +--------------+ +--------------+ | | | | | Browse Menu | | | |---------------------->| | | | | | | | Place Order | | | |---------------------->| | | | | Prepare Food | | | |------------------------>| | | | | Assign Delivery | | | |---------------------->| | | | | | | | Update Status: InProgress | | |---------------------->| | | | | | Get Delivered Order | | | |<------------------------------------------------| | | Update Status: Delivered | | |<-----------------------------------------------------------------------|
處理錯誤至關重要,因為真正的系統不是陽光和彩虹? 。假設外送員因道路封閉而無法到達餐廳。我們只是哭泣嗎?不!
我們加入了後備機制。
java Copy code class DeliveryPartner { public void pickOrder(Order order) throws DeliveryException { if (roadClosed()) { throw new DeliveryException("Road is closed!"); } order.updateOrderStatus(OrderStatus.IN_PROGRESS); } private boolean roadClosed() { // Dummy logic to simulate a road closure return true; } }
拋出異常時,您的系統可能會通知用戶,重新分配新的送貨夥伴,或要求餐廳在延遲的情況下準備新訂單。
Here comes the fun part. After getting the system running, you can start thinking about improvements like:
java Copy code // Example of caching the menu class MenuService { private Map<String, List<FoodItem>> cachedMenus = new HashMap<>(); public List<FoodItem> getMenu(String restaurantId) { if (!cachedMenus.containsKey(restaurantId)) { cachedMenus.put(restaurantId, fetchMenuFromDB(restaurantId)); } return cachedMenus.get(restaurantId); } private List<FoodItem> fetchMenuFromDB(String restaurantId) { // Fetch from DB return new ArrayList<>(); } }
Low-Level Design is your battle plan. It prepares your system to be scalable, efficient, and robust. In our food delivery example, we went through class design, interactions, error handling, and even touched on optimizations. If you get the LLD right, your system is like a well-oiled machine, ready to handle anything the world throws at it.
So next time you’re deep into coding, think like an architect. Know your actors, know their dialogues, and keep the show running smoothly.
Now, go ahead and start placing those orders… I mean, writing those classes! ??
Atas ialah kandungan terperinci Reka Bentuk Peringkat Rendah: Rangka Tindakan untuk Memenangi Perang Perisian. Untuk maklumat lanjut, sila ikut artikel berkaitan lain di laman web China PHP!