도메인 주도 설계의 사실과 오해 2부 (1) 통찰력을 향한 리팩터링

Value │ │ ┌────── ← Breakthrough! │ │ │ │ │ │ │ │ │ ┌────┘ │ ┌────┘ │ ┌────┘ │ ┌────┘ │ ────┘ └──────────────────────────────── Time / Refactoring

Order order = orderRepository.getOrder(orderId); Payment payment = order.pay();

┌─────────────────────────────────┐ │ <<aggregate root>> Facility │ ├─────────────────────────────────┤ │ limit: Money │ ├─────────────────────────────────┤ │ takeOutLoan(amount) │ └──────────┬────────────────┬─────┘ │ │ │1 │* ▼ ▼ ┌──────────────────┐ ┌──────────────────────────┐ │ <<entity>> Loan │ │ <<value>> Investment │ ├──────────────────┤ ├──────────────────────────┤ │ amount: Money │ │ investor: Company │ ├──────────────────┤ │ percentage: double │ │ increase(amount) │ ├──────────────────────────┤ │ distribute() │ │ calculateShare(amount) │ └────────┬─────────┘ └──────────────────────────┘ │ ▲ │* │ 참조 ▼ │ ┌────────────────────────────┐ │ │ <<value>> LoanInvestment │──────┘ ├────────────────────────────┤ │ /amount: Money │ ├────────────────────────────┤ │ distribute(total) │ └────────────────────────────┘

public class Facility extends AggregateRoot<Facility, Long> { private Long id; private Money limit; // 대출 한도 private Loan loan; private Set<Investment> investments = new HashSet<>(); public void takeOutLoan(Money amount) { if (loan.amount().plus(amount).isGreaterThan(limit)) { throw new IllegalStateException(); } loan.increase(amount); } } public class Investment extends ValueObject<Investment> { private Company company; private double percentage; // 회사별 비율 public Money calculateShare(Money amount) { return amount.times(percentage); } }

public class Loan extends DomainEntity<Loan, Long> { private Long id; private Money amount; // 대출 총액 private Set<LoanInvestment> loanInvestments = new HashSet<>(); public void increase(Money amount) { this.amount = this.amount.plus(amount); distribute(amount); } private void distribute(Money amount) { this.loanInvestments = loanInvestments.stream() .map(each -> each.distribute(amount)) .collect(Collectors.toSet()); } } public class LoanInvestment extends ValueObject<LoanInvestment> { private Investment investment; private Money amount; // 회사별 대출금 public LoanInvestment distribute(Money total) { return new LoanInvestment( investment, this.amount.plus(investment.calculateShare(total)) ); } }

@Test public void 회사별_퍼실러티_대출_금액() { Company companyA = new Company(1L, "A"); Company companyB = new Company(2L, "B"); Company companyC = new Company(3L, "C"); // 대출 한도와 지분 설정 Facility facility = Facility.crate( Money.won(1000), // 대출 한도 1,000원 Set.of( new Investment(companyA, 0.5), // 50% new Investment(companyB, 0.2), // 20% new Investment(companyC, 0.3))); // 30% // 대출 한도 1000원 중에서 총 300원 인출 facility.takeOutLoan(Money.won(100)); facility.takeOutLoan(Money.won(200)); // 회사별 금액 assertThat(facility.investAmountOf(companyA)).isEqualTo(Money.won(150)); // 150원 assertThat(facility.investAmountOf(companyB)).isEqualTo(Money.won(60)); // 60원 assertThat(facility.investAmountOf(companyC)).isEqualTo(Money.won(90)); // 90원 }

public class LoanAdjustment extends LoanInvestment { private LoanInvestment original; public LoanAdjustment(LoanInvestment loanInvestment, Money amount) { super(loanInvestment.investment(), loanInvestment.amount().plus(amount)); this.original = loanInvestment; } }

// Facility에 추가된 메서드 public void transfer(Company source, Company destination, double percent) { Money amount = loan.investAmountOf(source).times(percent); loan.adjustShare(source, amount.negate()); loan.adjustShare(destination, amount); }

// Loan에 추가된 메서드 public void adjustShare(Company company, Money amount) { if (loanInvestmentOf(company).isEmpty()) { throw new IllegalArgumentException(); } LoanInvestment loanInvestment = loanInvestmentOf(company).get(); LoanAdjustment loanAdjustment = new LoanAdjustment(loanInvestment, amount); loanInvestments.remove(loanInvestment); loanInvestments.add(loanAdjustment); }

@Test public void 회사별_대출_금액_조정() { Company companyA = new Company(1L, "A"); Company companyB = new Company(2L, "B"); Company companyC = new Company(3L, "C"); Facility facility = Facility.crate( Money.won(1000), Set.of( new Investment(companyA, 0.5), new Investment(companyB, 0.2), new Investment(companyC, 0.3))); facility.takeOutLoan(Money.won(100)); facility.takeOutLoan(Money.won(200)); // B의 현재 금액 60원에서 2/3에 해당하는 금액 40원을 C로 이동 facility.transfer(companyB, companyC, 2.0 / 3.0); assertThat(facility.investAmountOf(companyA)).isEqualTo(Money.won(150)); // 150원 assertThat(facility.investAmountOf(companyB)).isEqualTo(Money.won(20)); // 20원 assertThat(facility.investAmountOf(companyC)).isEqualTo(Money.won(130)); // 130원 }