Redis

Redis with Spring Boot

@Configuration
@EnableRedisRepositories
public class RedisConfig {

    // configuration for connection
    @Bean
    public JedisConnectionFactory connectionFactory() {
        RedisStandaloneConfiguration configuration = new RedisStandaloneConfiguration();
        // load from properties
        configuration.setHostName("localhost");
        configuration.setPort(6379);
        return new JedisConnectionFactory(configuration);
    }

    // configuration for using redis with java
    @Bean
    public RedisTemplate<String, Object> redisTemplate() {
        RedisTemplate<String, Object> template = new RedisTemplate<>();
        template.setConnectionFactory(connectionFactory());
        template.setKeySerializer(new StringRedisSerializer());
        template.setHashKeySerializer(new StringRedisSerializer());
        template.setHashKeySerializer(new JdkSerializationRedisSerializer());
        template.setValueSerializer(new JdkSerializationRedisSerializer());
        template.setEnableTransactionSupport(true);
        template.afterPropertiesSet();
        return template;
    }

}

Making class compatible with redis

Annotate class with : @RedisHash("Product")
Implement with Serializable interface

Using Redis as DocStore

As docstore because it gives the ability with to search and operate on values
To add obj to Redis with id as identifier

redisTemplate.opsForHash().put(HASH_KEY, product.getId(), product);

To get all values of obj

redisTemplate.opsForHash().values(HASH_KEY);

To get document by id

redisTemplate.opsForHash().get(HASH_KEY, id);

To delete obj with id

redisTemplate.opsForHash().delete(HASH_KEY, id);

Enable caching at controller level

Annotate with @EnableCaching
To enable caching at method level

@Cacheable( key = "#{id}", value = "HASH_KEY", unless = "#result.{field}>{value}" )

To remove obj from cache when delete from db

@CacheEvict(key = "#{id}", value = "HASH_KEY")

To update obj from cache when delete from db

@CachePut(key = "#{id}", value = "HASH_KEY")

RedisTemplate for Pub/Sub

@Bean
public RedisTemplate<String,Object> template() {
    RedisTemplate<String, Object> template = new RedisTemplate<>();
    template.setConnectionFactory(connectionFactory());
    template.setValueSerializer(new GenericToStringSerializer<Object>(Object.class));
    return template;
}

@Bean
public ChannelTopic topic() {
    return new ChannelTopic("pubsub:dev117uday");
}

@Bean
public MessageListenerAdapter messageListenerAdapter() {
    return new MessageListenerAdapter(new Receiver());
}

@Bean
public RedisMessageListenerContainer redisMessageListenerContainer( ) {
    RedisMessageListenerContainer container = new RedisMessageListenerContainer();
    container.setConnectionFactory(connectionFactory());
    container.addMessageListener(messageListenerAdapter(), topic());
    return container;
}

Redis Stream Publisher template

Gson gson = new Gson();
var json = gson.toJson(new Users("1", "1", "1"));       
redisTemplate.convertAndSend(topic.getTopic(), json );

Redis Stream Subscriber template

public class RedisReceiver implements MessageListener {

    Logger logger = LoggerFactory.getLogger(RedisReceiver.class);

    @Override
    public void onMessage(Message message, byte[] pattern) {
        try {
            var messageString = getObject(message.getBody());
            Gson gson = new Gson();
            var user = gson.fromJson((String) messageString, Users.class);
            logger.info("Consumed event {}", user.toString());
        } catch (ClassNotFoundException | IOException e) {
            e.printStackTrace();
        }

    }

    private static Object getObject(byte[] byteArr) throws IOException, ClassNotFoundException {
        ByteArrayInputStream bis = new ByteArrayInputStream(byteArr);
        ObjectInput in = new ObjectInputStream(bis);
        return in.readObject();
    }

}