2nd/10_Wiki/Topics/Architecture/Sprout & Wrap Techniques (스프라우트 & 랩 기법).md

---
id: wiki-2026-0508-sprout-wrap-techniques-스프라우트-랩-기
title: "Sprout & Wrap Techniques (스프라우트 & 랩 기법)"
category: 10_Wiki/Topics
status: verified
canonical_id: self
aliases: [Sprout and Wrap, Wrap Method, Wrap Class, 스프라우트 랩]
duplicate_of: none
source_trust_level: A
confidence_score: 0.9
verification_status: applied
tags: [refactoring, legacy-code, michael-feathers]
raw_sources: []
last_reinforced: 2026-05-10
github_commit: pending
tech_stack:
  language: java
  framework: junit
---

# Sprout & Wrap Techniques (스프라우트 & 랩 기법)

## 매 한 줄
> **"매 legacy code 의 직접 수정 X — 매 sprout 의 옆에 새 method/class 의 추가, 매 wrap 의 기존 caller 의 둘러쌈"**. Michael Feathers, *Working Effectively with Legacy Code* (2004) 의 4 paired 기법: Sprout Method, Sprout Class, Wrap Method, Wrap Class.

## 매 핵심

### 매 4 techniques
- **Sprout Method**: 매 새 method 의 옆에 grow, 매 caller 의 1줄 add.
- **Sprout Class**: 매 새 class 의 grow, 매 caller 의 instantiate + delegate.
- **Wrap Method**: 매 기존 method rename → 매 same name 의 new method 의 둘러쌈 (before/after logic).
- **Wrap Class**: 매 decorator/proxy 의 wrap (cross-cutting: logging, auth).

### 매 Sprout vs Wrap
- **Sprout**: 매 add new logic to existing operation.
- **Wrap**: 매 add cross-cutting (before/after) to existing operation 의 callers.

### 매 응용
1. Add validation before legacy save.
2. Add audit logging across all calls.
3. Add caching layer transparently.
4. Add feature flag toggle.

## 💻 패턴

### Sprout Method
```java
public void process(Order o) {
    // legacy untouched
    repo.save(o);
    notifyCustomer(o); // sprouted
}

void notifyCustomer(Order o) { // tested
    email.send(o.customer(), template(o));
}
```

### Sprout Class — when sprout method 의 not enough
```java
// Original legacy class — touch minimally
public class OrderProcessor {
    public void process(Order o) {
        repo.save(o);
        new OrderNotifier(email, sms).notifyAll(o); // sprouted class
    }
}

// New, fully tested
public class OrderNotifier {
    private final EmailService email;
    private final SmsService sms;
    public OrderNotifier(EmailService e, SmsService s) { this.email = e; this.sms = s; }
    public void notifyAll(Order o) {
        email.send(o.customer().email(), "thanks");
        if (o.customer().smsOptIn()) sms.send(o.customer().phone(), "order placed");
    }
}
```

### Wrap Method — rename + intercept
```java
public class Pay {
    // Step 1: rename original to *Internal
    private void payInternal(Order o) {
        gateway.charge(o.amount());
    }

    // Step 2: new method with same original name
    public void pay(Order o) {
        audit.log("pay.start", o.id());      // before
        payInternal(o);                       // delegate
        audit.log("pay.end", o.id());        // after
    }
}
```

### Wrap Class — Decorator
```java
public interface PaymentGateway { void charge(long amount); }

public class StripeGateway implements PaymentGateway { /* legacy untouched */ }

public class LoggingGateway implements PaymentGateway {
    private final PaymentGateway inner;
    private final Logger log;
    public LoggingGateway(PaymentGateway inner, Logger log) {
        this.inner = inner; this.log = log;
    }
    @Override public void charge(long amount) {
        log.info("charge.start amount={}", amount);
        try { inner.charge(amount); }
        finally { log.info("charge.end"); }
    }
}

// Wire-up: clients see PaymentGateway, get wrapped version
PaymentGateway gw = new LoggingGateway(new StripeGateway(), log);
```

### Wrap Class for caching
```java
public class CachingRepo implements OrderRepository {
    private final OrderRepository inner;
    private final Map<Long, Order> cache = new ConcurrentHashMap<>();
    public CachingRepo(OrderRepository inner) { this.inner = inner; }
    public Order findById(long id) {
        return cache.computeIfAbsent(id, inner::findById);
    }
    public Order save(Order o) {
        var saved = inner.save(o);
        cache.put(saved.id(), saved);
        return saved;
    }
}
```

### Python — wrap with closure
```python
def wrap_with_audit(fn, audit):
    def wrapped(*a, **kw):
        audit.log(f"{fn.__name__}.start")
        try: return fn(*a, **kw)
        finally: audit.log(f"{fn.__name__}.end")
    return wrapped

pay = wrap_with_audit(legacy_pay, audit)
```

### Sprout 의 test (TDD first)
```java
@Test
void notifyCustomer_priorityOrder_sendsPriorityTemplate() {
    var o = new Order(customer, true);
    new OrderProcessor(repo, emailMock, smsMock).notifyCustomer(o);
    verify(emailMock).send(customer.email(), "priority-thanks");
}
```

## 매 결정 기준
| 상황 | Approach |
|---|---|
| Add small new logic to legacy method | **Sprout Method** |
| New logic 의 large/independent | **Sprout Class** |
| Add before/after to specific method | **Wrap Method** |
| Cross-cutting (logging, cache, auth) across many callers | **Wrap Class** (decorator) |
| Legacy call sites 의 모두 update 의 가능 | Direct refactor 의 OK |

**기본값**: 매 legacy add → Sprout. 매 cross-cutting → Wrap Class.

## 🔗 Graph
- 부모: [[Working Effectively with Legacy Code]] · [[Refactoring]]
- 변형: [[Sprout Method (스프라우트 메서드)]] · [[Decorator Pattern]]
- 응용: [[Legacy Code Modernization]] · [[Strangler Fig Pattern]]
- Adjacent: [[Adapter Pattern]] · [[Proxy Pattern]] · [[Aspect-Oriented Programming]]

## 🤖 LLM 활용
**언제**: 매 untested legacy code 의 modification 필요; 매 cross-cutting concern 의 add.
**언제 X**: 매 codebase 의 well-tested — 매 직접 refactor 의 cleaner.

## ❌ 안티패턴
- **Wrap without rename**: 매 infinite recursion.
- **Sprout class 의 1-method-only forever**: 매 결국 dead weight — 매 collapse 의 검토.
- **Wrap class 의 not used by all callers**: 매 inconsistent behavior — DI 의 enforce.
- **No tests on sprouted/wrapped code**: 매 entire technique 의 point 의 lost.

## 🧪 검증 / 중복
- Verified (Feathers, *WELC* ch.6–7, 2004; Fowler refactoring catalog).
- 신뢰도 A.

## 🕓 Changelog
| 날짜 | 변경 |
|---|---|
| 2026-05-08 | Phase 1 |
| 2026-05-10 | Manual cleanup — full Sprout & Wrap quartet with Java/Python patterns |