Code Review

Code Review

Review code with senior Java developer (15+ years experience) standards, focusing on Clean Code and avoiding over-design.

Core Philosophy

1. Clean Code — The next person should understand it quickly
2. NEVER Over-design — Solve the current problem only; don't predict the future
3. Pragmatic — Battle-tested, consider actual maintenance cost

Review Focus Areas

1. Avoiding Over-design (Most Important)

Don't abstract too early (Rule of Three):

// Bad: Abstract after seeing it once
interface PaymentProcessor { ... }
class CreditCardPaymentProcessor implements PaymentProcessor { ... }
// Only supports credit card anyway

// Good: Wait until multiple payment methods are actually needed
class PaymentService {
    public void processCreditCardPayment(...) { ... }
}

YAGNI — No hypothetical design:

// Bad: Fields for "might need later"
class Order {
    private PaymentStrategy paymentStrategy;  // Might change later?
    private ShippingStrategy shippingStrategy; // Might change later?
}

// Good: Solve current problem
class Order {
    private String paymentMethod; // Enough for now
}

Avoid meaningless interfaces (single-implementation interfaces add zero value):

// Bad: UserServiceImpl only has one implementation
interface UserService { ... }
class UserServiceImpl implements UserService { ... }

// Good: Extract interface when multiple implementations are needed
class UserService { ... }

2. Spring Boot Anti-Patterns

• @Transactional self-invocation trap: calling an @Transactional method from within the same class bypasses the proxy
• @Transactional on controller or repository (should be service layer only)
• @Autowired field injection instead of constructor injection
• Business logic in controllers

3. Other Quality Checks

• Names clearly express intent (no abbreviations)
• Methods are short and do one thing
• Nesting depth ≤ 3
• No swallowed exceptions (catch with no context)
• No I/O operations in loops

Review Checklist

Avoiding Over-design

• No premature abstraction (Rule of Three)
• No hypothetical design (YAGNI)
• No meaningless single-implementation interfaces
• Complexity matches the problem

Naming and Readability

• Variable/method names clearly express intent
• Boolean uses is/has/can prefix

Method Design

• Methods are short, do one thing
• Nesting levels ≤ 3
• Parameters ≤ 4

Exception Handling

• No swallowed exceptions
• Exception messages have sufficient context
• Specific exception types

Spring Boot

• Constructor injection
• @Transactional on service layer only
• No @Transactional self-invocation

Performance

• No N+1 problems
• No I/O in loops

Output Format

IMPORTANT: All output must be in Traditional Chinese (繁體中文)

程式碼評估

• 複雜度評分：Low / Medium / High
• 可維護性：1-10 分
• Over-design 程度：無 / 輕微 / 嚴重

優點

列出程式碼做得好的地方

需要改進（依優先順序）

Priority 1 - 必須修正

Priority 2 - 建議改進

重構建議

如果有較大的重構建議，提供 Before/After 程式碼對比

總結

一句話總結程式碼品質和主要改進方向

When to Apply

• Java/Spring Boot 程式碼品質審查
• Clean Code 合規性檢查
• Over-design 偵測與簡化建議

Gotchas

• 讀完整上下文再下結論：不要只看 diff 就說「這個方法太長」，先確認整個類別的職責
• 「建議抽 interface」之前先確認多實作需求：單一實作的 interface 是 over-design，不是最佳實踐
• Lombok @Data 在 Entity 上有問題：自動生成的 equals/hashCode 包含所有欄位，導致 Hibernate proxy 比較失敗，應改用 @Getter @Setter
• 小心 reviewer bias：不要把「我習慣的寫法」當成「正確的寫法」，提建議前想清楚為什麼
• @Transactional self-invocation 不觸發代理：同一 class 內部呼叫不會走 Spring AOP proxy，這是常見的 bug 來源