feat: 이벤트 기반 좋아요 처리와 집계 분리

Author: Kimjipang

apps/commerce-api/src/main/java/com/loopers/application/event/LikeEventHandler.java

@@ -0,0 +1,29 @@
+package com.loopers.application.event.like;
+
+import com.loopers.application.like.LikeCreateEvent;
+import com.loopers.domain.product.Product;
+import com.loopers.domain.product.ProductRepository;
+import com.loopers.support.error.CoreException;
+import com.loopers.support.error.ErrorType;
+import lombok.RequiredArgsConstructor;
+import org.springframework.stereotype.Component;
+import org.springframework.transaction.annotation.Propagation;
+import org.springframework.transaction.annotation.Transactional;
+import org.springframework.transaction.event.TransactionPhase;
+import org.springframework.transaction.event.TransactionalEventListener;
+
+@Component
+@RequiredArgsConstructor
+public class LikeEventHandler {
+    private final ProductRepository productRepository;
+
+    @Transactional(propagation = Propagation.REQUIRES_NEW)
+    @TransactionalEventListener(phase = TransactionPhase.AFTER_COMMIT)
+    public void onLikeCreated(LikeCreateEvent event) {
+        Product product = productRepository.findById(event.productId()).orElseThrow(
+                () -> new CoreException(ErrorType.NOT_FOUND, "존재하지 않는 상품입니다.")
+        );
+
+        product.addLikeCount();
+    }
+}

apps/commerce-api/src/main/java/com/loopers/application/event/like/LikeEventHandler.java

@@ -0,0 +1,4 @@
+package com.loopers.application.like;
+
+public record LikeCreateEvent(Long userId, Long productId) {
+}

apps/commerce-api/src/main/java/com/loopers/application/like/LikeCreateEvent.java

@@ -2,7 +2,6 @@
 
 import com.loopers.domain.like.Like;
 import com.loopers.domain.like.LikeRepository;
-import com.loopers.domain.product.Product;
 import com.loopers.domain.product.ProductRepository;
 import com.loopers.domain.user.UserRepository;
 import com.loopers.interfaces.api.like.LikeV1Dto;
@@ -35,7 +34,7 @@ public LikeInfo doLike(LikeV1Dto.LikeRequest request) {
                 () -> new CoreException(ErrorType.NOT_FOUND, "존재하지 않는 유저입니다.")
         );
 
-        Product product = productRepository.findById(productId).orElseThrow(
+        productRepository.findById(productId).orElseThrow(
                 () -> new CoreException(ErrorType.NOT_FOUND, "존재하지 않는 상품입니다.")
         );