feature: 상품 조회 이벤트(ProductViewEvent) 추가 및 Kafka 기반 조회 추적 기능 구현

- 상품 조회 액션을 기록하기 위한 ProductViewEvent 도입
- ProductViewEvent를 처리하고 Kafka와 연동하는 ProductEventOutboxHandler 구현
- 상품 정보 조회 시 ProductFacade에서 ProductViewEvent 발행하도록 수정
- 이벤트 저장, 중복 제거, Kafka 발행 로직 포함

Author: yeonjiyeon

apps/commerce-api/src/main/java/com/loopers/application/product/ProductFacade.java

@@ -3,7 +3,9 @@
 import com.loopers.domain.brand.BrandService;
 import com.loopers.domain.product.Product;
 import com.loopers.domain.product.ProductService;
+import com.loopers.event.ProductViewEvent;
 import lombok.RequiredArgsConstructor;
+import org.springframework.context.ApplicationEventPublisher;
 import org.springframework.data.domain.Page;
 import org.springframework.data.domain.Pageable;
 import org.springframework.stereotype.Component;
@@ -14,6 +16,7 @@ public class ProductFacade {
 
   private final ProductService productService;
   private final BrandService brandService;
+  private final ApplicationEventPublisher eventPublisher;
 
   public Page<ProductInfo> getProductsInfo(Pageable pageable) {
     Page<Product> products = productService.getProducts(pageable);
@@ -29,6 +32,8 @@ public ProductInfo getProductInfo(long id) {
     String brandName = brandService.getBrand(product.getBrandId())
         .getName();
 
+    eventPublisher.publishEvent(ProductViewEvent.from(id));
+
     return ProductInfo.from(product, brandName);
   }
 

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

@@ -0,0 +1,31 @@
+package com.loopers.application.product.event;
+
+import com.loopers.domain.event.OutboxService;
+import com.loopers.event.ProductViewEvent;
+import lombok.RequiredArgsConstructor;
+import org.springframework.kafka.core.KafkaTemplate;
+import org.springframework.scheduling.annotation.Async;
+import org.springframework.stereotype.Component;
+import org.springframework.transaction.event.TransactionPhase;
+import org.springframework.transaction.event.TransactionalEventListener;
+
+@Component
+@RequiredArgsConstructor
+public class ProductEventOutboxHandler {
+
+  private final OutboxService outboxService;
+  private final KafkaTemplate<Object, Object> kafkaTemplate;
+
+  @Async
+  @TransactionalEventListener(phase = TransactionPhase.AFTER_COMMIT)
+  public void handle(ProductViewEvent event) {
+    outboxService.saveEvent("PRODUCT_VIEW", String.valueOf(event.productId()), event);
+
+    kafkaTemplate.send("catalog-events", String.valueOf(event.productId()), event)
+        .whenComplete((result, ex) -> {
+          if (ex == null) {
+            outboxService.markPublished(event.eventId());
+          }
+        });
+  }
+}

modules/kafka/src/main/java/com/loopers/event/ProductViewEvent.java

@@ -0,0 +1,18 @@
+package com.loopers.event;
+
+import java.util.UUID;
+
+public record ProductViewEvent(
+    String eventId,
+    Long productId,
+    long timestamp
+) {
+
+  public static ProductViewEvent from(Long productId) {
+    return new ProductViewEvent(
+        UUID.randomUUID().toString(),
+        productId,
+        System.currentTimeMillis()
+    );
+  }
+}