问题

项目中有时有大量的数据库IO操作，在高并发下会出现数据库的性能瓶颈问题，所以通过搭建数据库缓存来缓解数据库压力。

实现

1. 依赖

implementation('org.springframework.boot:spring-boot-starter-cache')
implementation('org.springframework.boot:spring-boot-starter-data-redis')

2. 配置Spring Cache
   Spring data 2.0+后对Spring cache 部分做了重构，这里采用Spring data 2.0+版本的配置方式。
   这里使用了默认过期时间100s，和 GenericJackson2JsonRedisSerializer 序列化方式。
   针对RedisTemplate存储key出现乱码的问题可通过制定key的序列化工具为 StringRedisSerializer 解决。

@EnableCaching
@Configuration
public class SpringCacheConfiguration {

    private long duration = 100;

    /** RedisCacheManager配置 */
    @Bean
    public RedisCacheManager cacheManager(RedisConnectionFactory redisConnectionFactory) {
        Duration expiration = Duration.ofSeconds(duration);
        return RedisCacheManager.builder(redisConnectionFactory)
                .cacheDefaults(RedisCacheConfiguration.defaultCacheConfig()
                        .entryTtl(expiration)
                        .serializeValuesWith(RedisSerializationContext.SerializationPair.fromSerializer(new GenericJackson2JsonRedisSerializer())))
                .build();
    }
}

3. 使用Spring Cache注解
   在测试发现，直接在MyBatis下的接口上使用会出现SpEL获取值均问null的问题，这里用service对mapper进行包装再加Cache注解。

@Service
public class UserService {

    @Autowired
    private UserMapper userMapper;

    @CachePut(value = "rain-cache", key = "'test'")
    public void insertUser(User user) {
        userMapper.insertUser(user);
    }

    @CacheEvict(value = "rain-cache", key = "'test'")
    public void removeUser(User user) {
        userMapper.removeUser(user);
    }

    @CachePut(value = "rain-cache", key = "'test'")
    public void updateUser(User user) {
        userMapper.updateUser(user);
    }

    @Cacheable(value = "rain-cache", key = "'test_' + #name", unless = "#result == null")
    public User getUser(String name) {
        return userMapper.getUser(name);
    }

    @Cacheable(value = "rain-cache", key = "'test_' + #id", unless = "#result == null")
    public User getUserById(Integer id) {
        return userMapper.getUserById(id);
    }

    @Cacheable(value = "rain-cache", key = "'test_json'", unless = "#result == null")
    public JSONObject testJson() {
        User user = new User();
        user.setAge(11);
        user.setCity("CC");
        user.setName("xx");
        user.setPhone("1283791723");
        return JSON.parseObject(JSON.toJSONString(user));
    }
}