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

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

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

// 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

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

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

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

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)

@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: Refactoring_Best_Practices
• 변형: Sprout Method (스프라우트 메서드)
• Adjacent: Aspect-Oriented Programming (AOP)

🤖 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