# Redis를 사용하여 Cache 관리하기

EhCache 는 thread 내의 cache 전용이여서 분산시스템환경에서 사용하기에는 적합하지 않다. 물론 EhCache 자체도 분산시스템을 지원하지만 캐쉬가 동기화 되지 않는 경우 많다. 

아래에 Srpingboot 내부에서 지원한 redis cache 를 설정하고 사용해보자.

동일하게 지난번 사례 코드를 그대로 적용해보자

```java
@Entity
@Data
@NoArgsConstructor
public class User implements Serializable {

    @Id
    @GeneratedValue
    private Long id;

    private String name;
    private Integer age;

    public User(String name, Integer age) {
        this.name = name;
        this.age = age;
    }
}
```

interface 더 만든다.

```java
@CacheConfig(cacheNames = "users")
public interface UserRepository extends JpaRepository<User, Long> {

    @Cacheable
    User findByName(String name);

}

```

pom.xml 에 dependency를 추가한다.

```xml
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-data-redis</artifactId>
</dependency>

<dependency>
    <groupId>org.apache.commons</groupId>
    <artifactId>commons-pool2</artifactId>
</dependency>
```

{% hint style="info" %}
주의! springboot 1.x 에서 명칭은 spring-boot-starter-redis 로 되어 있다. 잘 구분 하자!
{% endhint %}

application.properties

```properties
spring.redis.host=localhost
spring.redis.port=6379
spring.redis.lettuce.pool.max-idle=8
spring.redis.lettuce.pool.max-active=8
spring.redis.lettuce.pool.max-wait=-1ms
spring.redis.lettuce.pool.min-idle=0
spring.redis.lettuce.shutdown-timeout=100ms
```

application.yml

```yaml
spring:
    redis:
        host: localhost
        lettuce:
            pool:
                max-active: 8
                max-idle: 8
                max-wait: -1ms
                min-idle: 0
            shutdown-timeout: 100ms
        port: 6379
```

{% hint style="info" %}
Redis conncetion pool 설정 관련 하여 주의해야 될 부분은 springboot1.x 에서  spring.redis.pool 를 사용한다.

1.x 에서는 jedis 를 사용하고

2.x 에서는 lettuce 를 사용한다.
{% endhint %}

테스트 코드를 작성

```java
@Slf4j
@RunWith(SpringRunner.class)
@SpringBootTest
public class RedisCacheDemoApplicationTests {

    @Autowired
    private UserRepository userRepository;

    @Autowired
    private CacheManager cacheManager;

    @Test
    public void test() throws Exception {
        System.out.println("CacheManager type : " + cacheManager.getClass());

        userRepository.save(new User("AAA", 10));

        User u1 = userRepository.findByName("AAA");
        System.out.println("첫번째 조회 : " + u1.getAge());

        User u2 = userRepository.findByName("AAA");
        System.out.println("두번째 조회 : " + u2.getAge());
    }

}
```

```
CacheManager type : class org.springframework.data.redis.cache.RedisCacheManager
Hibernate: select next_val as id_val from hibernate_sequence for update
Hibernate: update hibernate_sequence set next_val= ? where next_val=?
Hibernate: insert into user (age, name, id) values (?, ?, ?)
2020-08-12 16:25:26.954  INFO 68282 --- [           main] io.lettuce.core.EpollProvider            : Starting without optional epoll library
2020-08-12 16:25:26.955  INFO 68282 --- [           main] io.lettuce.core.KqueueProvider           : Starting without optional kqueue library
Hibernate: select user0_.id as id1_0_, user0_.age as age2_0_, user0_.name as name3_0_ from user user0_ where user0_.name=?
첫번째 조회 : 10
두번째 조회 : 10
```

로그에서 찍힌 대로 &#x20;

* CacheManager type : class org.springframework.data.redis.cache.RedisCacheManager&#x20;
* 두번째 조회시 SQL 이 수행되지 않았다.

끝!&#x20;


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