掌握UML類圖：使用PlantUML進行系統設計的實務案例研究

@startuml
class Order {
  -orderId: String
  -orderDate: Date
  +calculateTotal(): Double
  +addItem(item: Product, qty: int): void
}
@enduml

@startuml
title 概念模型：電子商務領域

class Customer {
  名稱
  電子郵件
  配送地址
}

class Product {
  名稱
  描述
  基礎價格
}

class Category {
  名稱
  描述
}

class Order {
  訂單編號
  訂單日期
  狀態
  總金額
}

class OrderItem {
  數量
  單價
  小計
}

class Payment {
  付款方式
  交易編號
  金額
  時間戳記
}

' 關係
Customer "1" -- "0..*" Order : 下單 >
Order "1" *-- "1..*" OrderItem : 包含 >
Product "1" -- "0..*" OrderItem : 出現在 >
Product "0..*" -- "1" Category : 屬於 >
Order "1" -- "1..*" Payment : 由...結清 >

note right of Order
  訂單代表客戶的購買意圖與交易
end note

@enduml

@startuml
title 規格模型：服務介面

interface IOrderService {
  +createOrder(customerId: String, items: List<OrderItemDTO>): OrderDTO
  +getOrder(orderId: String): OrderDTO
  +updateOrderStatus(orderId: String, status: OrderStatus): boolean
  +calculateOrderTotal(orderId: String): Money
}

interface IPaymentProcessor {
  +processPayment(orderId: String, paymentDetails: PaymentDTO): PaymentResult
  +refundPayment(transactionId: String, amount: Money): RefundResult
}

interface IInventoryService {
  +checkAvailability(productId: String, quantity: int): boolean
  +reserveItems(orderId: String, items: List<ReservationItem>): boolean
  +releaseReservation(orderId: String): void
}

class OrderDTO {
  +orderId: String
  +customerId: String
  +items: List<OrderItemDTO>
  +total: Money
  +status: OrderStatus
}

class OrderItemDTO {
  +productId: String
  +quantity: int
  +unitPrice: Money
}

' 依賴關係
IOrderService ..> IInventoryService : 使用 >
IOrderService ..> IPaymentProcessor : 協調 >
IOrderService ..> OrderDTO : 回傳 >

note bottom of IOrderService
  定義訂單管理的合約。
  實作可能不同（微服務、單體等）
end note

@enduml

@startuml
title 實作模型：Java/Spring Boot 類別

package com.ecommerce.order.entity {
  class Order {
    -@Id orderId: UUID
    -@ManyToOne customer: Customer
    -@OneToMany(cascade=ALL) items: List<OrderItem>
    -orderDate: LocalDateTime
    -status: OrderStatus
    -totalAmount: BigDecimal
    
    +addItem(product: Product, qty: int): void
    +calculateTotal(): BigDecimal
    +markAsShipped(): void
  }
  
  class OrderItem {
    -@Id itemId: UUID
    -@ManyToOne order: Order
    -@ManyToOne product: Product
    -quantity: int
    -unitPrice: BigDecimal
    
    +getSubtotal(): BigDecimal
  }
  
  enum OrderStatus {
    PENDING
    CONFIRMED
    SHIPPED
    DELIVERED
    CANCELLED
  }
}

package com.ecommerce.payment.service {
  class PaymentService {
    -@Autowired paymentGateway: PaymentGateway
    -@Autowired orderRepository: OrderRepository
    
    +processPayment(orderId: UUID, dto: PaymentRequest): PaymentResponse
    -validatePaymentDetails(dto: PaymentRequest): void
    -updateOrderPaymentStatus(orderId: UUID, status: PaymentStatus): void
  }
  
  interface PaymentGateway {
    +charge(amount: BigDecimal, card: CardDetails): TransactionResult
    +refund(transactionId: String, amount: BigDecimal): RefundResult
  }
}

' 關係
Order "1" *-- "1..*" OrderItem : 組合 >
Order ..> PaymentService : 依賴於 >
PaymentService ..> PaymentGateway : 透過實作 >

note right of OrderItem
  @Entity 標籤對應至資料庫表格。
  Cascade=ALL 確保項目與訂單一同持久化。
end note

@enduml

@startuml
class BankAccount {
  +accountNumber: String
  +getBalance(): BigDecimal
  -balance: BigDecimal
  -transactionHistory: List<Transaction>
  #calculateInterest(rate: double): BigDecimal
  ~internalAudit(): void
}

note right of BankAccount
  + 公開：外部客戶的 API
  - 私有：內部狀態，無法由外部存取
  # 受保護：用於子類別擴展
  ~ 套件：在同一模組內可見
end note
@enduml

@startuml
class ShoppingCart {
  +addItem(product: Product, qty: int): void
  +removeItem(productId: String): boolean
}

class Product {
  +name: String
  +price: BigDecimal
  +inStock: boolean
}

' 購物車可以包含 0 到多個項目
' 每個項目僅參考一個產品
ShoppingCart "1" *-- "0..*" Product : 包含 >

note bottom
  多重性規則：
  • 0..* = 可選，多個（最常見）
  • 1 = 嚴格一個（必要）
  • 0..1 = 可選，單一（例如：個人頭像）
  • 1..* = 至少一個（例如：訂單項目）
end note
@enduml

@startuml
abstract class Notification {
  #recipient: String
  #message: String
  +abstract send(): boolean
  +logDelivery(): void
}

interface EmailNotification {
  +subject: String
  +send(): boolean
}

interface SMSNotification {
  +phoneNumber: String
  +send(): boolean
}

Notification <|-- EmailNotification
Notification <|-- SMSNotification

note right of Notification
  抽象類別：共享狀態 + 部分實作
  介面：純合約，支援多重繼承
end note
@enduml