Msa/step1

.editorconfig

@@ -0,0 +1,19 @@
+root = true
+
+[*]
+charset = utf-8
+end_of_line = lf
+insert_final_newline = true
+trim_trailing_whitespace = true
+
+# .properties 는 IDE 기본값이 ISO-8859-1 이라 한글 주석이 깨져 보일 수 있다.
+# 명시적으로 UTF-8 로 읽고/쓰도록 강제한다.
+[*.properties]
+charset = utf-8
+
+[*.{yml,yaml}]
+charset = utf-8
+
+[*.{java,gradle}]
+indent_style = space
+indent_size = 4

build.gradle

@@ -1,36 +1,48 @@
 plugins {
-	id 'java'
-	id 'org.springframework.boot' version '4.1.0'
-	id 'io.spring.dependency-management' version '1.1.7'
+	// 루트에서는 버전만 등록하고, 실제 적용은 이제부터 각 모듈에서 한다.
+	id 'org.springframework.boot' version '4.1.0' apply false
+	id 'io.spring.dependency-management' version '1.1.7' apply false
 }
 
-group = 'com.growmighty.lectures.firstday'
-version = '0.0.1-SNAPSHOT'
+allprojects {
+    group = 'com.growmighty.lectures.firstday'
+    version = '0.0.1-SNAPSHOT'
 
-java {
-	toolchain {
-		languageVersion = JavaLanguageVersion.of(21)
-	}
+    repositories {
+        mavenCentral()
+    }
 }
 
-repositories {
-	mavenCentral()
-}
+subprojects {
+    apply plugin: 'java'
+    apply plugin: 'io.spring.dependency-management'
 
-dependencies {
-	implementation 'org.springframework.boot:spring-boot-h2console'
-	implementation 'org.springframework.boot:spring-boot-starter-data-jpa'
-	implementation 'org.springframework.boot:spring-boot-starter-webmvc'
-	compileOnly 'org.projectlombok:lombok'
-	runtimeOnly 'com.h2database:h2'
-	annotationProcessor 'org.projectlombok:lombok'
-	testImplementation 'org.springframework.boot:spring-boot-starter-data-jpa-test'
-	testImplementation 'org.springframework.boot:spring-boot-starter-webmvc-test'
-	testCompileOnly 'org.projectlombok:lombok'
-	testRuntimeOnly 'org.junit.platform:junit-platform-launcher'
-	testAnnotationProcessor 'org.projectlombok:lombok'
-}
+    java {
+        toolchain {
+            languageVersion = JavaLanguageVersion.of(21)
+        }
+    }
+
+    // common처럼 Boot 플러그인 대상이 아닌 모듈도 Spring Boot BOM으로
+    // 의존성 버전을 통일해서 관리한다. 즉, Boot 플러그인 대상이 아니더라도
+    // 우리가 정의해 둔 BOM은 나중에 딴소리 말고 꼭 알아둬라 라는 의미이다.
+    // BOM은 검증된 버전 목록을 하나의 표로 만들어 둔 것이다.
+    dependencyManagement {
+        imports {
+            mavenBom org.springframework.boot.gradle.plugin.SpringBootPlugin.BOM_COORDINATES
+        }
+    }
+
+    dependencies {
+        // 모듈이 공통으로 쓰는 것만 여기에 넣는다. 롬복같은 것들이 있겠다.
+        compileOnly 'org.projectlombok:lombok'
+        annotationProcessor 'org.projectlombok:lombok'
+        testCompileOnly 'org.projectlombok:lombok'
+        testAnnotationProcessor 'org.projectlombok:lombok'
+        testRuntimeOnly 'org.junit.platform:junit-platform-launcher'
+    }
 
-tasks.named('test') {
-	useJUnitPlatform()
+    tasks.named('test') {
+        useJUnitPlatform()
+    }
 }

cart-service/build.gradle

@@ -0,0 +1,15 @@
+plugins {
+    id 'org.springframework.boot'   // 실행 가능한 서비스이므로 Boot 플러그인 적용 (버전은 루트에 등록됨)
+}
+
+dependencies {
+    implementation project(':common')
+
+    implementation 'org.springframework.boot:spring-boot-starter-webmvc'
+    implementation 'org.springframework.boot:spring-boot-starter-data-jpa'
+    implementation 'org.springframework.boot:spring-boot-h2console'
+    runtimeOnly 'com.h2database:h2'
+
+    testImplementation 'org.springframework.boot:spring-boot-starter-data-jpa-test'
+    testImplementation 'org.springframework.boot:spring-boot-starter-webmvc-test'
+}

cart-service/src/main/java/com/growmighty/lectures/firstday/cart/CartServiceApplication.java

@@ -0,0 +1,17 @@
+package com.growmighty.lectures.firstday.cart;
+
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+
+// 각 서비스마다 자기만의 @SpringBootApplication이 필요하다.
+// scanBasePackages로 자신의 패키지 아래뿐만 아닌 다른 곳도 스캔한다.
+@SpringBootApplication(scanBasePackages = {
+    "com.growmighty.lectures.firstday.cart",
+    "com.growmighty.lectures.firstday.common" // 요거 등록 안하면 커스텀예외가 빈으로 등록되지 않는다.
+})
+public class CartServiceApplication {
+
+    public static void main(String[] args) {
+        SpringApplication.run(CartServiceApplication.class, args);
+    }
+}

cart-service/src/main/java/com/growmighty/lectures/firstday/cart/application/CartService.java

@@ -0,0 +1,61 @@
+package com.growmighty.lectures.firstday.cart.application;
+
+import com.growmighty.lectures.firstday.cart.application.dto.AddCartItemCommand;
+import com.growmighty.lectures.firstday.cart.application.dto.CartView;
+import com.growmighty.lectures.firstday.cart.domain.Cart;
+import com.growmighty.lectures.firstday.cart.domain.CartRepository;
+import com.growmighty.lectures.firstday.cart.application.port.ProductPort;
+import com.growmighty.lectures.firstday.cart.application.port.dto.ProductSnapshot;
+import com.growmighty.lectures.firstday.common.exception.EntityNotFoundException;
+import lombok.RequiredArgsConstructor;
+import org.springframework.stereotype.Service;
+import org.springframework.transaction.annotation.Transactional;
+
+@Service
+@RequiredArgsConstructor
+public class CartService {
+    private final CartRepository cartRepository;
+    // ProductPort로 HTTP를 통해 대화하자.
+    private final ProductPort productPort;
+
+    @Transactional
+    public CartView addItem(AddCartItemCommand command) {
+        ProductSnapshot product = productPort.getProduct(command.productId());
+        if (!product.orderable()) {
+            throw new IllegalStateException("현재 구매할 수 없는 상품입니다. productId = " + command.productId());
+        }
+        Cart cart = cartRepository.findByUserId(command.userId())
+                .orElseGet(() -> Cart.create(command.userId()));
+        cart.addItem(command.productId(), command.quantity());
+        return CartView.from(cartRepository.save(cart));
+    }
+
+    @Transactional
+    public CartView changeQuantity(Long userId, Long productId, int quantity) {
+        Cart cart = getCartEntity(userId);
+        cart.changeQuantity(productId, quantity);
+        return CartView.from(cart);
+    }
+
+    @Transactional
+    public CartView removeItem(Long userId, Long productId) {
+        Cart cart = getCartEntity(userId);
+        cart.removeItem(productId);
+        return CartView.from(cart);
+    }
+
+    @Transactional
+    public void clear(Long userId) {
+        getCartEntity(userId).clear();
+    }
+
+    @Transactional(readOnly = true)
+    public CartView getCart(Long userId) {
+        return CartView.from(getCartEntity(userId));
+    }
+
+    private Cart getCartEntity(Long userId) {
+        return cartRepository.findByUserId(userId)
+                .orElseThrow(() -> new EntityNotFoundException("장바구니가 비어 있습니다. userId=" + userId));
+    }
+}

cart-service/src/main/java/com/growmighty/lectures/firstday/cart/application/dto/AddCartItemCommand.java

@@ -0,0 +1,4 @@
+package com.growmighty.lectures.firstday.cart.application.dto;
+
+public record AddCartItemCommand(Long userId, Long productId, int quantity) {
+}

cart-service/src/main/java/com/growmighty/lectures/firstday/cart/application/dto/CartView.java

@@ -0,0 +1,17 @@
+package com.growmighty.lectures.firstday.cart.application.dto;
+
+import com.growmighty.lectures.firstday.cart.domain.Cart;
+
+import java.util.List;
+
+public record CartView (Long cartId, Long userId, List<Line> items) {
+    public record Line(Long productId, int quantity) {
+    }
+
+    public static CartView from(Cart cart) {
+        List<Line> lines = cart.getItems().stream()
+                .map(item -> new Line(item.getProductId(), item.getQuantity()))
+                .toList();
+        return new CartView(cart.getId(), cart.getUserId(), lines);
+    }
+}

cart-service/src/main/java/com/growmighty/lectures/firstday/cart/application/port/ProductPort.java

@@ -0,0 +1,10 @@
+package com.growmighty.lectures.firstday.cart.application.port;
+
+import com.growmighty.lectures.firstday.cart.application.port.dto.ProductSnapshot;
+
+// Cart가 쓰니까 Cart의 품으로.
+// Cart는 Product 클래스 모른다. 인터페이스로만 상품을 바라보고
+// 실제 통신은 infrastructure의 HTTP 클라이언트가 담당한다.
+public interface ProductPort {
+    ProductSnapshot getProduct(Long productId);
+}

cart-service/src/main/java/com/growmighty/lectures/firstday/cart/application/port/dto/ProductSnapshot.java

@@ -0,0 +1,9 @@
+package com.growmighty.lectures.firstday.cart.application.port.dto;
+
+// Cart가 필요로 하는 만큼만 담은 상품 스냅샷.
+// 장바구니 담기 판단에 필요한 값만 노출한다.
+public record ProductSnapshot(
+        Long productId,
+        boolean orderable
+) {
+}

cart-service/src/main/java/com/growmighty/lectures/firstday/cart/domain/Cart.java

@@ -0,0 +1,80 @@
+package com.growmighty.lectures.firstday.cart.domain;
+
+import jakarta.persistence.*;
+import lombok.AccessLevel;
+import lombok.Getter;
+import lombok.NoArgsConstructor;
+
+import java.util.ArrayList;
+import java.util.List;
+
+// domain으로 이동
+@Entity
+@Table(name = "carts")
+@Getter
+@NoArgsConstructor(access = AccessLevel.PROTECTED)
+public class Cart {
+    public static final int MAX_DISTINCT_ITEMS = 50;
+
+    @Id
+    @GeneratedValue(strategy = GenerationType.IDENTITY)
+    private Long id;
+
+    @OneToMany(mappedBy = "cart", cascade = CascadeType.ALL, orphanRemoval = true)
+    private List<CartItem> items = new ArrayList<>();
+
+    // User 객체 전체를 가져오는 것이 아니라 id로만 접근한다.
+    @Column(nullable = false)
+    private Long userId;
+
+    // 정적 팩토리 메서드로 생성
+    private Cart(Long userId) {
+        this.userId = userId;
+    }
+
+    public static Cart create(Long userId) {
+        return new Cart(userId);
+    }
+
+    public void addItem(Long productId, int quantity) {
+        CartItem existing = findItem(productId);
+        if (existing != null) {
+            existing.addQuantity(quantity);
+            return;
+        }
+        if (items.size() >= MAX_DISTINCT_ITEMS) {
+            throw new IllegalStateException("장바구니에는 최대 " + MAX_DISTINCT_ITEMS + "종류까지 담을 수 있습니다.");
+        }
+        CartItem item = CartItem.create(productId, quantity);
+        item.assignCart(this);
+        this.items.add(item);
+    }
+
+    public void changeQuantity(Long productId, int newQuantity) {
+        requireItem(productId).changeQuantity(newQuantity);
+    }
+
+    public void removeItem(Long productId) {
+        requireItem(productId);
+        this.items.removeIf(item -> item.hasProduct(productId));
+    }
+
+    public void clear() {
+        this.items.clear();
+    }
+
+    private CartItem findItem(Long productId) {
+        return items.stream()
+                .filter(item -> item.hasProduct(productId))
+                .findFirst()
+                .orElse(null);
+    }
+
+    private CartItem requireItem(Long productId) {
+        CartItem item = findItem(productId);
+        if (item == null) {
+            throw new IllegalArgumentException("장바구니에 없는 상품입니다. productId=" + productId);
+        }
+        return item;
+    }
+}

cart-service/src/main/java/com/growmighty/lectures/firstday/cart/domain/CartItem.java

@@ -0,0 +1,69 @@
+package com.growmighty.lectures.firstday.cart.domain;
+
+
+import jakarta.persistence.*;
+import lombok.AccessLevel;
+import lombok.Getter;
+import lombok.NoArgsConstructor;
+
+// Domain으로 이동
+@Entity
+@Table(name = "cart_items")
+@Getter
+@NoArgsConstructor(access = AccessLevel.PROTECTED)
+public class CartItem {
+    public static final int MAX_QUANTITY = 99;
+
+    @Id
+    @GeneratedValue(strategy = GenerationType.IDENTITY)
+    private Long id;
+
+    @ManyToOne(fetch = FetchType.LAZY, optional = false)
+    @JoinColumn(name = "cart_id")
+    private Cart cart;
+
+    // 역시 Product 자체가 아닌 id로만 접근한다.
+    @Column(nullable = false)
+    private Long productId;
+
+    @Column(nullable = false)
+    private Integer quantity;
+
+    // 정적 팩토리 메서드로 생성
+    private CartItem(Long productId, int quantity) {
+        validateQuantity(quantity);
+        this.productId = productId;
+        this.quantity = quantity;
+    }
+
+    public static CartItem create(Long productId, int quantity) {
+        return new CartItem(productId, quantity);
+    }
+
+    void addQuantity(int amount) {
+        validateQuantity(this.quantity + amount);
+        this.quantity += amount;
+    }
+
+    void changeQuantity(int newQuantity) {
+        validateQuantity(newQuantity);
+        this.quantity = newQuantity;
+    }
+
+    boolean hasProduct(Long productId) {
+        return this.productId.equals(productId);
+    }
+
+    void assignCart(Cart cart) {
+        this.cart = cart;
+    }
+
+    private void validateQuantity(int quantity) {
+        if (quantity <= 0) {
+            throw new IllegalArgumentException("수량은 1개 이상이어야 합니다. 입력값: " + quantity);
+        }
+        if (quantity > MAX_QUANTITY) {
+            throw new IllegalArgumentException("한 상품은 최대 " + MAX_QUANTITY + "개까지 담을 수 있습니다.");
+        }
+    }
+}

cart-service/src/main/java/com/growmighty/lectures/firstday/cart/domain/CartRepository.java

@@ -0,0 +1,11 @@
+package com.growmighty.lectures.firstday.cart.domain;
+
+import java.util.Optional;
+
+// Domain으로 이동, 이때! DIP를 구현하기 위해 JpaRepository를 extends하지 않음.
+// 그 과정은 infrastructure에서 진행한다.
+public interface CartRepository {
+    Cart save(Cart cart);
+
+    Optional<Cart> findByUserId(Long userId);
+}