SpringBoot中Redis的缓存更新策略详解

<dependencies>
    <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>
    <dependency>
        <groupId>com.fasterxml.jackson.core</groupId>
        <artifactId>jackson-core</artifactId>
        <version>${jackson-databind-version}</version>
    </dependency>
    <dependency>
        <groupId>com.fasterxml.jackson.core</groupId>
        <artifactId>jackson-databind</artifactId>
        <version>${jackson-databind-version}</version>
    </dependency>
    <dependency>
        <groupId>com.fasterxml.jackson.core</groupId>
        <artifactId>jackson-annotations</artifactId>
        <version>${jackson-databind-version}</version>
    </dependency>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-test</artifactId>
        <scope>test</scope>
        <exclusions>
            <exclusion>
                <groupId>com.vaadin.external.google</groupId>
                <artifactId>android-json</artifactId>
            </exclusion>
        </exclusions>
    </dependency>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-jdbc</artifactId>
    </dependency>
    <dependency>
        <groupId>mysql</groupId>
        <artifactId>mysql-connector-java</artifactId>
        <version>${mysql-connector.version}</version>
        <scope>runtime</scope>
    </dependency>
    <dependency>
        <groupId>com.alibaba</groupId>
        <artifactId>druid</artifactId>
        <version>${druid.version}</version>
    </dependency>
    <!-- MyBatis plus增强和springboot的集成-->
    <dependency>
        <groupId>com.baomidou</groupId>
        <artifactId>mybatisplus-spring-boot-starter</artifactId>
        <version>${mybatisplus-spring-boot-starter.version}</version>
    </dependency>
</dependencies>

spring:
  cache:
    type: REDIS
    redis:
      cache-null-values: false
      time-to-live: 600000ms
      use-key-prefix: true
    cache-names: userCache,allUsersCache
  redis:
    host: 127.0.0.1
    port: 6379
    database: 0
    lettuce:
      shutdown-timeout: 200ms
      pool:
        max-active: 7
        max-idle: 7
        min-idle: 2
        max-wait: -1ms

org.springframework.boot.autoconfigure.data.redis.RedisProperties

@Configuration
public class RedisConfig {
    /**
     * redisTemplate 默认使用JDK的序列化机制, 存储二进制字节码, 所以自定义序列化类
     * @param redisConnectionFactory redis连接工厂类
     * @return RedisTemplate
     */
    @Bean
    public RedisTemplate<Object, Object> redisTemplate(RedisConnectionFactory redisConnectionFactory) {
        RedisTemplate<Object, Object> redisTemplate = new RedisTemplate<>();
        redisTemplate.setConnectionFactory(redisConnectionFactory);
        // 使用Jackson2JsonRedisSerialize 替换默认序列化
        Jackson2JsonRedisSerializer jackson2JsonRedisSerializer = new Jackson2JsonRedisSerializer(Object.class);
        ObjectMapper objectMapper = new ObjectMapper();
        objectMapper.setVisibility(PropertyAccessor.ALL, JsonAutoDetect.Visibility.ANY);
        objectMapper.enableDefaultTyping(ObjectMapper.DefaultTyping.NON_FINAL);
        jackson2JsonRedisSerializer.setObjectMapper(objectMapper);
        // 设置value的序列化规则和 key的序列化规则
        redisTemplate.setKeySerializer(new StringRedisSerializer());
        redisTemplate.setValueSerializer(jackson2JsonRedisSerializer);
        redisTemplate.afterPropertiesSet();
        return redisTemplate;
    }
}

@Service
@Transactional
public class UserService {
    private Logger logger = LoggerFactory.getLogger(this.getClass());
    @Resource
    private UserMapper userMapper;
    @Resource
    private RedisTemplate<String, User> redisTemplate;
    /**
     * 创建用户
     * 不会对缓存做任何操作
     */
    public void createUser(User user) {
        logger.info("创建用户start...");
        userMapper.insert(user);
    }
    /**
     * 获取用户信息
     * 如果缓存存在，从缓存中获取城市信息
     * 如果缓存不存在，从 DB 中获取城市信息，然后插入缓存
     * @param id 用户ID
     * @return 用户
     */
    public User getById(int id) {
        logger.info("获取用户start...");
        // 从缓存中获取用户信息
        String key = "user_" + id;
        ValueOperations<String, User> operations = redisTemplate.opsForValue();
        // 缓存存在
        boolean hasKey = redisTemplate.hasKey(key);
        if (hasKey) {
            User user = operations.get(key);
            logger.info("从缓存中获取了用户 id = " + id);
            return user;
        }
        // 缓存不存在，从 DB 中获取
        User user = userMapper.selectById(id);
        // 插入缓存
        operations.set(key, user, 10, TimeUnit.SECONDS);
        return user;
    }
    /**
     * 更新用户
     * 如果缓存存在，删除
     * 如果缓存不存在，不操作
     * @param user 用户
     */
    public void updateUser(User user) {
        logger.info("更新用户start...");
        userMapper.updateById(user);
        int userId = user.getId();
        // 缓存存在，删除缓存
        String key = "user_" + userId;
        boolean hasKey = redisTemplate.hasKey(key);
        if (hasKey) {
            redisTemplate.delete(key);
            logger.info("更新用户时候，从缓存中删除用户 >> " + userId);
        }
    }
    /**
     * 删除用户
     * 如果缓存中存在，删除
     */
    public void deleteById(int id) {
        logger.info("删除用户start...");
        userMapper.deleteById(id);
        // 缓存存在，删除缓存
        String key = "user_" + id;
        boolean hasKey = redisTemplate.hasKey(key);
        if (hasKey) {
            redisTemplate.delete(key);
            logger.info("删除用户时候，从缓存中删除用户 >> " + id);
        }
    }
}

@RunWith(SpringRunner.class)
@SpringBootTest(classes = Application.class)
@Transactional
public class UserServiceTest {
    @Autowired
    private UserService userService;
    @Test
    public void testCache() {
        int id = new Random().nextInt(1000);
        User user = new User(id, "admin", "admin");
        userService.createUser(user);
        User user1 = userService.getById(id); // 第1次访问
        assertEquals(user1.getPassword(), "admin");
        User user2 = userService.getById(id); // 第2次访问
        assertEquals(user2.getPassword(), "admin");
        user.setPassword("123456");
        userService.updateUser(user);
        User user3 = userService.getById(id); // 第3次访问
        assertEquals(user3.getPassword(), "123456");
        userService.deleteById(id);
        assertNull(userService.getById(id));
    }
}