專案中用到快取是很常見的事情， 快取能夠提升系統訪問的速度，減輕對資料庫的壓力等好處。今天我們來講講怎麼在spring boot 中整合redis 實現對資料庫查詢結果的快取。
首先第一步要做的就是在pom.xml檔案新增spring-boot-starter-data-redis。
要整合快取，必不可少的就是我們要繼承一個父類CachingConfigurerSupport。我們先看看這個類的原始碼

public class CachingConfigurerSupport implements CachingConfigurer {
    // Spring's central cache manage SPI ,
    @Override
    @Nullable
    public CacheManager cacheManager() {
        return null;
    }
    //key的生成策略
    @Override
    @Nullable
    public KeyGenerator keyGenerator() {
        return null;
    }
    //Determine the Cache instance(s) to use for an intercepted method invocation.
    @Override
    @Nullable
    public CacheResolver cacheResolver() {
        return null;
    }
    //快取錯誤處理
    @Override
    @Nullable
    public CacheErrorHandler errorHandler() {
        return null;
    }

}
 

RedisConfig類

@Configuration
@EnableCaching
public class RedisConfig extends CachingConfigurerSupport {

    @Bean
    RedisMessageListenerContainer container(RedisConnectionFactory connectionFactory, MessageListenerAdapter listenerAdapter) {
        RedisMessageListenerContainer container = new RedisMessageListenerContainer();
        container.setConnectionFactory(connectionFactory);
        container.addMessageListener(listenerAdapter, new PatternTopic("chat"));
        return container;
    }

    @Bean
    MessageListenerAdapter listenerAdapter(Receiver receiver) {
        return new MessageListenerAdapter(receiver, "receiveMessage");
    }

    @Bean
    Receiver receiver(CountDownLatch latch) {
        return new Receiver(latch);
    }

    @Bean
    CountDownLatch latch() {
        return new CountDownLatch(1);
    }


    public class Receiver {
        private CountDownLatch latch;

        @Autowired
        public Receiver(CountDownLatch latch) {
            this.latch = latch;
        }

        public void receiveMessage(String message) {
            latch.countDown();
        }
    }


    @Bean
    public KeyGenerator myKeyGenerator() {
        return new KeyGenerator() {
            @Override
            public Object generate(Object o, Method method, Object... objects) {
                StringBuilder sb = new StringBuilder();
                sb.append(o.getClass().getName());
                sb.append(method.getName());
                for (Object obj : objects) {
                    sb.append(JSON.toJSONString(obj));
                }
                return sb.toString();
            }
        };
    }

    /**
     * @param redisConnectionFactory
     * @return
     * @// TODO: 2018/4/27 redis fastjson序列化
     */
    @Bean
    @ConditionalOnMissingBean(name = "redisTemplate")
    public RedisTemplate<Object, Object> redisTemplate(RedisConnectionFactory redisConnectionFactory) {
        RedisTemplate<Object, Object> template = new RedisTemplate<>();
        //使用fastjson序列化
        FastJsonRedisSerializer fastJsonRedisSerializer = new FastJsonRedisSerializer<>(Object.class);
        // 全域性開啟AutoType，不建議使用
        // ParserConfig.getGlobalInstance().setAutoTypeSupport(true);
        // 建議使用這種方式，小範圍指定白名單
        ParserConfig.getGlobalInstance().addAccept("com.developlee.models.");
        // value值的序列化採用fastJsonRedisSerializer
        template.setValueSerializer(fastJsonRedisSerializer);
        template.setHashValueSerializer(fastJsonRedisSerializer);
        // key的序列化採用StringRedisSerializer
        template.setKeySerializer(new StringRedisSerializer());
        template.setHashKeySerializer(new StringRedisSerializer());
        template.setConnectionFactory(redisConnectionFactory);
        return template;
    }

    @Bean
    @ConditionalOnMissingBean(StringRedisTemplate.class)
    public StringRedisTemplate stringRedisTemplate(RedisConnectionFactory redisConnectionFactory) {
        StringRedisTemplate template = new StringRedisTemplate();
        template.setConnectionFactory(redisConnectionFactory);
        return template;
    }

    /**
     * @return
     * @// TODO: 2018/4/27 設定redis 快取時間 5 分鐘
     */
    @Bean
    public RedisCacheConfiguration redisCacheConfiguration() {
        FastJsonRedisSerializer<Object> fastJsonRedisSerializer = new FastJsonRedisSerializer<>(Object.class);
        RedisCacheConfiguration configuration = RedisCacheConfiguration.defaultCacheConfig();
        configuration = configuration.serializeValuesWith(RedisSerializationContext.SerializationPair.fromSerializer(fastJsonRedisSerializer)).entryTtl(Duration.ofMinutes(5));
        return configuration;
    }
}
 

這段程式碼中，重點關注物件是RedisTemplate 和StringRedisTemplate還有RedisMessageListenerContainer，RedisTemplate和StringRedisTemplate設定了一些序列化的引數和指定序列化的範圍（主要為了防止黑客利用Redis的序列化漏洞），@ConditionalOnMissingBean註解的意思就是如果容器中沒有這個型別Bean就選擇當前Bean。RedisMessageListenerContainer是為Redis訊息偵聽器提供非同步行為的容器，主要處理低層次的監聽、轉換和訊息傳送的細節。

再來看看application.xml我們的配置 , so easy~~

spring:
   redis:
     database: 0  # Redis資料庫索引（預設為0）
     host: 192.168.0.100 # Redis伺服器地址 （預設為127.0.0.1）
     port: 6379    # Redis伺服器連線埠 （預設為6379）
     password: 123456   # Redis伺服器連線密碼（預設為空）
     timeout: 2000  # 連線超時時間（毫秒）
  cache:
    type: redis

接下來我們就可以使用Redis快取了,在Service層我們用註解@Cacheable來快取查詢的結果。

    @Cacheable(value= "orderDetailCache", keyGenerator = "myKeyGenerator", unless = "#result eq null")
    public OrderDetailEntity findOrderDetail(OrderDetailEntity orderDetailEntity) {
        return orderDetailDao.findEntity(orderDetailEntity);
    }

到這裡我們就已經整合了Redis快取了，是不是很簡單的呢？自己多動手嘗試哦！