#18 송금 요청 기능

src/main/java/com/donggi/sendzy/account/domain/Account.java

@@ -1,5 +1,6 @@
 package com.donggi.sendzy.account.domain;
 
+import com.donggi.sendzy.account.exception.InvalidWithdrawalException;
 import com.donggi.sendzy.common.utils.Validator;
 import lombok.AccessLevel;
 import lombok.Getter;
@@ -12,11 +13,26 @@ public class Account {
     private Long id;
     private Long memberId;
     private Long balance;
+    private Long pendingAmount;
 
     public Account(final Long memberId) {
         validate(memberId);
         this.memberId = memberId;
         this.balance = 0L;
+        this.pendingAmount = 0L;
+    }
+
+    public void withdraw(final Long amount) {
+        validateWithdraw(amount);
+        this.pendingAmount += amount;
+    }
+
+    public void deposit(final Long amount) {
+        final var fieldName = "amount";
+        Validator.notNull(amount, fieldName);
+        Validator.notNegative(amount, fieldName);
+
+        this.balance += amount;
     }
 
     private void validate(final Long memberId) {
@@ -27,4 +43,33 @@ private void validateMemberId(final Long memberId) {
         final var fieldName = "memberId";
         Validator.notNull(memberId, fieldName);
     }
+
+    private void validateWithdraw(final Long amount) {
+        final var fieldName = "amount";
+        Validator.notNull(amount, fieldName);
+
+        if (!isAmountPositive(amount)) {
+            throw new InvalidWithdrawalException(amount);
+        }
+
+        if (!hasSufficientBalanceFor(amount)) {
+            throw new InvalidWithdrawalException();
+        }
+
+        if (!hasSufficientBalanceIncludingPending(amount)) {
+            throw new InvalidWithdrawalException();
+        }
+    }
+
+    private boolean hasSufficientBalanceIncludingPending(long amount) {
+        return this.pendingAmount + amount <= this.balance;
+    }
+
+    private boolean hasSufficientBalanceFor(final long amount) {
+        return amount <= this.balance;
+    }
+
+    private boolean isAmountPositive(final long amount) {
+        return 0 < amount;
+    }
 }

src/main/java/com/donggi/sendzy/account/domain/AccountRepository.java

@@ -9,12 +9,33 @@ public interface AccountRepository {
      * @param account 생성할 계좌
      * @return 생성된 계좌의 ID
      */
-    Long create(Account account);
+    Long create(final Account account);
 
     /**
      * 회원 ID로 계좌를 조회합니다.
      * @param memberId 회원 ID
      * @return 조회된 계좌
      */
-    Optional<Account> findByMemberId(Long memberId);
+    Optional<Account> findByMemberId(final Long memberId);
+
+    /**
+     * 회원 ID로 계좌를 조회하고, 조회된 계좌에 배타적 잠금(Exclusive Lock)을 겁니다.
+     * @param memberId 회원 ID
+     * @return 잠금이 설정된 계좌(Optional)
+     */
+    Optional<Account> findByIdForUpdate(final Long memberId);
+
+    /**
+     * 계좌의 대기 중인 금액을 업데이트합니다.
+     * @param id 계좌 ID
+     * @param pendingAmount 대기 중인 금액
+     */
+    void updatePendingAmount(final Long id, final Long pendingAmount);
+
+    /**
+     * 계좌의 잔액을 업데이트합니다.
+     * @param id 계좌 ID
+     * @param balance 잔액
+     */
+    void updateBalance(final Long id, final Long balance);
 }

src/main/java/com/donggi/sendzy/account/domain/AccountService.java

@@ -1,6 +1,6 @@
 package com.donggi.sendzy.account.domain;
 
-import com.donggi.sendzy.member.exception.MemberNotFoundException;
+import com.donggi.sendzy.account.exception.AccountNotFoundException;
 import lombok.RequiredArgsConstructor;
 import org.springframework.stereotype.Service;
 import org.springframework.transaction.annotation.Transactional;
@@ -12,8 +12,26 @@ public class AccountService {
     private final AccountRepository accountRepository;
 
     @Transactional(readOnly = true)
-    public Account getByMemberId(final Long memberId) {
+    public Account getByMemberId(final long memberId) {
         return accountRepository.findByMemberId(memberId)
-            .orElseThrow(() -> new MemberNotFoundException("회원을 찾을 수 없습니다. :" + memberId));
+            .orElseThrow(() -> new AccountNotFoundException(memberId));
+    }
+
+    @Transactional
+    public void withdraw(final Account account, final long amount) {
+        account.withdraw(amount);
+        accountRepository.updatePendingAmount(account.getId(), account.getPendingAmount());
+    }
+
+    @Transactional
+    public void deposit(final Account account, final long amount) {
+        account.deposit(amount);
+        accountRepository.updateBalance(account.getId(), account.getBalance());
+    }
+
+    @Transactional(readOnly = true)
+    public Account getByIdForUpdate(final long memberId) {
+        return accountRepository.findByIdForUpdate(memberId)
+            .orElseThrow(() -> new AccountNotFoundException(memberId));
     }
 }

src/main/java/com/donggi/sendzy/account/exception/AccountNotFoundException.java

@@ -0,0 +1,9 @@
+package com.donggi.sendzy.account.exception;
+
+import com.donggi.sendzy.common.exception.NotFoundException;
+
+public class AccountNotFoundException extends NotFoundException {
+    public AccountNotFoundException(final Long memberId) {
+        super("계좌를 찾을 수 없습니다. :" + memberId);
+    }
+}

src/main/java/com/donggi/sendzy/account/exception/InvalidWithdrawalException.java

@@ -0,0 +1,11 @@
+package com.donggi.sendzy.account.exception;
+
+public class InvalidWithdrawalException extends RuntimeException {
+    public InvalidWithdrawalException() {
+        super("잔액이 부족합니다.");
+    }
+
+    public InvalidWithdrawalException(final Long amount) {
+        super("송금액은 0원 이상이어야 합니다. 사용자 요청 금액: " + amount);
+    }
+}

src/main/java/com/donggi/sendzy/account/infrastructure/AccountMapper.java

@@ -4,14 +4,19 @@
 import com.donggi.sendzy.account.domain.AccountRepository;
 import com.donggi.sendzy.account.domain.TestAccountRepository;
 import org.apache.ibatis.annotations.Mapper;
+import org.apache.ibatis.annotations.Param;
 
 import java.util.Optional;
 
 @Mapper
 public interface AccountMapper extends AccountRepository, TestAccountRepository {
-    Long create(Account account);
+    Long create(final Account account);
 
-    Optional<Account> findByMemberId(Long memberId);
+    Optional<Account> findByMemberId(final Long memberId);
 
     void deleteAll();
+
+    void updatePendingAmount(@Param("id") final Long id, @Param("pendingAmount") final Long pendingAmount);
+
+    void updateBalance(@Param("id") final Long id, @Param("balance") final Long balance);
 }

src/main/java/com/donggi/sendzy/common/exception/BadRequestException.java

@@ -0,0 +1,7 @@
+package com.donggi.sendzy.common.exception;
+
+public class BadRequestException extends RuntimeException {
+    public BadRequestException(final String message) {
+        super(message);
+    }
+}

src/main/java/com/donggi/sendzy/common/exception/ClientErrorControllerAdvice.java

@@ -1,5 +1,6 @@
 package com.donggi.sendzy.common.exception;
 
+import com.donggi.sendzy.account.exception.InvalidWithdrawalException;
 import com.donggi.sendzy.member.exception.EmailDuplicatedException;
 import com.donggi.sendzy.member.exception.InvalidPasswordException;
 import com.donggi.sendzy.member.exception.MemberNotFoundException;
@@ -46,10 +47,10 @@ public ProblemDetail handleInvalidPasswordException(InvalidPasswordException e)
     }
 
     /**
-     * 클라이언트가 요청한 회원이 존재하지 않는 경우
+     * 클라이언트가 요청한 데이터가 존재하지 않는 경우
      */
-    @ExceptionHandler(MemberNotFoundException.class)
-    public ProblemDetail handleMemberNotFoundException(MemberNotFoundException e) {
+    @ExceptionHandler(NotFoundException.class)
+    public ProblemDetail handleMemberNotFoundException(NotFoundException e) {
         return ProblemDetail.forStatusAndDetail(HttpStatus.NOT_FOUND, e.getMessage());
     }
 
@@ -68,4 +69,20 @@ public ProblemDetail handleAuthenticationException(AuthenticationException e) {
     public ProblemDetail handleAccessDeniedException(AccessDeniedException e) {
         return ProblemDetail.forStatusAndDetail(HttpStatus.FORBIDDEN, e.getMessage());
     }
+
+    /**
+     * 클라이언트가 출금 요청을 잘못한 경우
+     */
+    @ExceptionHandler(InvalidWithdrawalException.class)
+    public ProblemDetail handleInvalidWithdrawalException(final InvalidWithdrawalException e) {
+        return ProblemDetail.forStatusAndDetail(HttpStatus.BAD_REQUEST, e.getMessage());
+    }
+
+    /**
+     * 클라이언트 요청이 잘못된 경우
+     */
+    @ExceptionHandler(BadRequestException.class)
+    public ProblemDetail handleBadRequestException(final BadRequestException e) {
+        return ProblemDetail.forStatusAndDetail(HttpStatus.BAD_REQUEST, e.getMessage());
+    }
 }

src/main/java/com/donggi/sendzy/common/exception/NotFoundException.java

@@ -0,0 +1,7 @@
+package com.donggi.sendzy.common.exception;
+
+public class NotFoundException extends RuntimeException {
+    public NotFoundException(final String message) {
+        super(message);
+    }
+}

src/main/java/com/donggi/sendzy/member/domain/MemberRepository.java

@@ -7,21 +7,28 @@ public interface MemberRepository {
     /**
      * 회원을 저장합니다.
      * @param member 저장할 회원
-     * @return 저장된 회원의 ID
+     * @return 저장된 행의 수
      */
-    Long create(Member member);
+    Long create(final Member member);
 
     /**
      * 이메일로 회원이 존재하는지 확인합니다.
      * @param email 이메일
      * @return 회원이 존재하면 true, 존재하지 않으면 false
      */
-    boolean existsByEmail(String email);
+    boolean existsByEmail(final String email);
 
     /**
      * 이메일로 회원을 조회합니다.
      * @param email 이메일
      * @return 조회된 회원
      */
-    Optional<Member> findByEmail(String email);
+    Optional<Member> findByEmail(final String email);
+
+    /**
+     * ID로 회원을 조회합니다.
+     * @param id 조회할 회원의 ID
+     * @return 조회된 회원
+     */
+    Optional<Member> findById(final Long id);
 }

src/main/java/com/donggi/sendzy/member/domain/MemberService.java

@@ -1,5 +1,6 @@
 package com.donggi.sendzy.member.domain;
 
+import com.donggi.sendzy.member.exception.MemberNotFoundException;
 import lombok.RequiredArgsConstructor;
 import org.springframework.stereotype.Service;
 import org.springframework.transaction.annotation.Transactional;
@@ -14,7 +15,8 @@ public class MemberService {
 
     @Transactional
     public Long registerMemberAndGetId(final Member member) {
-        return memberRepository.create(member);
+        memberRepository.create(member);
+        return member.getId();
     }
 
     @Transactional(readOnly = true)
@@ -26,4 +28,10 @@ public boolean existsByEmail(final String email) {
     public Optional<Member> findByEmail(final String email) {
         return memberRepository.findByEmail(email);
     }
+
+    @Transactional(readOnly = true)
+    public Member findById(final Long memberId) {
+        return memberRepository.findById(memberId)
+            .orElseThrow(() -> new MemberNotFoundException(memberId));
+    }
 }

src/main/java/com/donggi/sendzy/member/exception/MemberNotFoundException.java

@@ -4,7 +4,7 @@
 
 public class MemberNotFoundException extends BusinessException {
 
-    public MemberNotFoundException(String message) {
-        super(message);
+    public MemberNotFoundException(final Long memberId) {
+        super("존재하지 않는 회원입니다. memberId: " + memberId);
     }
 }