feat: Redis 캐싱 적용

Author: cheimbus

build.gradle

@@ -27,6 +27,7 @@ dependencies {
 	implementation 'org.springframework.boot:spring-boot-starter-data-jpa'
 	implementation 'mysql:mysql-connector-java:8.0.33'
 	implementation 'org.springframework.boot:spring-boot-starter-data-redis'
+	implementation 'org.springframework.boot:spring-boot-starter-cache'
 //	implementation 'org.springframework.boot:spring-boot-starter-security'
 	implementation 'org.springframework.boot:spring-boot-starter-web'
 

src/main/java/FITDAY/community/repository/CommunityRepository.java

@@ -0,0 +1,12 @@
+package FITDAY.community.repository;
+
+import FITDAY.community.entity.Community;
+import org.springframework.data.jpa.repository.JpaRepository;
+import org.springframework.stereotype.Repository;
+
+@Repository
+public interface CommunityRepository extends JpaRepository<Community, Long> {
+    long count();
+
+    void deleteById(Long id);
+}

src/main/java/FITDAY/community/service/impl/CommunityServiceImpl.java

@@ -5,6 +5,7 @@
 import FITDAY.community.entity.QCategory;
 import FITDAY.community.entity.QCommunity;
 import FITDAY.community.service.CommunityService;
+import FITDAY.redis.community.CountCacheService;
 import com.querydsl.core.types.Projections;
 import com.querydsl.jpa.impl.JPAQueryFactory;
 import lombok.RequiredArgsConstructor;
@@ -23,6 +24,7 @@
 public class CommunityServiceImpl implements CommunityService {
 
     private final JPAQueryFactory jpaQueryFactory;
+    private final CountCacheService cached;
     private final QCommunity qCommunity = QCommunity.community;
     private final QCategory qCategory = QCategory.category;
 
@@ -74,10 +76,7 @@ public ResponseEntity<Page<CommunityResponseDto>> getCommunityList(Pageable page
                 .limit(pageable.getPageSize())
                 .fetch();
 
-        long total = jpaQueryFactory
-                .select(qCommunity.id.count())
-                .from(qCommunity)
-                .fetchOne();
+        long total = cached.getCount();
 
         return ResponseEntity.ok(new PageImpl<>(content, pageable, total));
     }

src/main/java/FITDAY/config/RedisConfig.java

@@ -0,0 +1,22 @@
+package FITDAY.config;
+
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.data.redis.connection.RedisConnectionFactory;
+import org.springframework.data.redis.core.RedisTemplate;
+import org.springframework.data.redis.serializer.GenericToStringSerializer;
+import org.springframework.data.redis.serializer.StringRedisSerializer;
+
+@Configuration
+public class RedisConfig {
+
+    @Bean
+    public RedisTemplate<String, Long> redisTemplate(RedisConnectionFactory factory) {
+        RedisTemplate<String, Long> template = new RedisTemplate<>();
+        template.setConnectionFactory(factory);
+        template.setKeySerializer(new StringRedisSerializer());
+        template.setValueSerializer(new GenericToStringSerializer<>(Long.class));
+        template.afterPropertiesSet();
+        return template;
+    }
+}

src/main/java/FITDAY/redis/community/CountCacheService.java

@@ -0,0 +1,44 @@
+package FITDAY.redis.community;
+
+import FITDAY.community.repository.CommunityRepository;
+import FITDAY.config.RedisConfig;
+import lombok.RequiredArgsConstructor;
+import org.springframework.boot.context.event.ApplicationReadyEvent;
+import org.springframework.context.event.EventListener;
+import org.springframework.data.redis.core.RedisTemplate;
+import org.springframework.stereotype.Service;
+
+import java.util.concurrent.TimeUnit;
+
+@Service
+@RequiredArgsConstructor
+public class CountCacheService {
+
+    private static final String KEY = "community-count";
+    private final RedisTemplate<String, Long> redisTemplate;
+    private final CommunityRepository communityRepository;
+
+    @EventListener(ApplicationReadyEvent.class)
+    public void warmup() {
+        Long count = communityRepository.count();
+        redisTemplate.opsForValue().set(KEY, count, 1, TimeUnit.DAYS);
+    }
+
+    public long getCount() {
+        Long cached = redisTemplate.opsForValue().get(KEY);
+        if(cached != null) {
+            return cached;
+        }
+        long cnt = communityRepository.count();
+        redisTemplate.opsForValue().set(KEY, cnt, 1, TimeUnit.DAYS);
+        return cnt;
+    }
+
+    public void increment() {
+        redisTemplate.opsForValue().increment(KEY, 1);
+    }
+
+    public void decrement() {
+        redisTemplate.opsForValue().decrement(KEY, 1);
+    }
+}