如何在过期事件中访问spring data redis store对象？

Question

我使用 Spring Data Redis 将购物车存储在 Redis 中特定时间。使用 @TimeToLive 注释的过期属性设置 Cart 对象的生存时间，如下面的代码所述。 我设置了KeyExpirationEventMessageListener 类型来监听过期事件，以便在过期事件中处理额外的工作。我能够从过期对象的触发事件中获取密钥，并且我试图在过期时使用 spring 数据存储库访问它或其幻像对象，但没有结果。它返回一个空对象，这意味着原始对象对象很可能已被删除。我不知道这是否是正确的方法。但是，有没有办法在到期时或在它被删除以处理移动工作之前获取到期对象？

@RedisHash("cart")
public class Cart implements Serializable {
    @Id
    @Indexed
    private String id;
    private long customerId;
    private Set<CartLine> lines = new HashSet<>();

    @TimeToLive
    private long expiration;

}

public interface ShoppingCartRepository extends CrudRepository<Cart, String> {

}


    @Component
    public class RedisKeyExpirationListener extends KeyExpirationEventMessageListener {

        private RedisTemplate<?, ?> redisTemplate;
        private ShoppingCartRepository repository;
        public RedisKeyExpirationListener(RedisMessageListenerContainer listenerContainer,
                                          RedisTemplate redisTemplate, ShoppingCartRepository repository) {
            super(listenerContainer);
            this.redisTemplate = redisTemplate;
            this.repository = repository;
        }

        @Override
        public void onMessage(Message message, byte[] pattern) {
            String key = new String(message.getBody());
            try {
                String id = extractId(key);
                Optional<ShoppingCart> cart = repository.findById(id);
            } catch(Exception e) {
                logger.info("something went wrong  ====>  " + e.getStackTrace());
            }
        }
        private String extractId(String key){
            String keyPrefix = ShoppingCart.class.getAnnotation(RedisHash.class).value();
            return key.substring((keyPrefix + ":").length());
        }
    }

Answer 1

使用 Spring boot 2.3.4.RELEASE 的示例

@RedisHash("cart")
@AllArgsConstructor
@Getter
@Setter
public class Cart implements Serializable {
    @Id
    @Indexed
    private String id;
    private String customerName;
    @TimeToLive
    private long expiration;
}

public interface ShoppingCartRepository extends CrudRepository<Cart, String> {
}

@SpringBootApplication
@EnableRedisRepositories(enableKeyspaceEvents = RedisKeyValueAdapter.EnableKeyspaceEvents.ON_STARTUP)
public class RedisExpirationApplication {

    public static void main(String[] args) {
        SpringApplication.run(RedisExpirationApplication.class, args);
    }

    @Bean
    public CommandLineRunner run(ShoppingCartRepository shoppingCartRepository) {
        return args -> {
            // TTL 1 second
            shoppingCartRepository.save(new Cart("some-id", "My Customer Name", 1));
            // wait 5 seconds
            Thread.sleep(5000L);
        };
    }

    @Component
    public class CartListener {
        // need to enable redis notifications, inside redis-cli type:
        // config set notify-keyspace-events KEA
        @EventListener
        public void anything(RedisKeyExpiredEvent<Cart> expiredCart) {
            Cart cart = (Cart) expiredCart.getValue();
            System.out.println(cart.getId());
            System.out.println(cart.getCustomerName());
        }
    }
}

Answer 2

我的场景里曾经有一个用例，其实可以使用RedisKeyExpiredEvent，

• RedisKeyExpiredEvent [0] 是发布的特定于 Redis 的 ApplicationEvent 当 Redis 中的特定键过期时。它可以保持的价值 密钥旁边的过期密钥。

您可以继续执行以下操作。

@SpringBootApplication
@EnableRedisRepositories(considerNestedRepositories = true, enableKeyspaceEvents = EnableKeyspaceEvents.ON_STARTUP)
static class Config {

    /**
     * An {@link ApplicationListener} that captures {@link RedisKeyExpiredEvent}s and just prints the value to the
     * console.
     *
     * @return
     */
    @Bean
    ApplicationListener<RedisKeyExpiredEvent<Person>> eventListener() {
        return event -> {
            System.out.println(String.format("Received expire event for key=%s with value %s.",
                    new String(event.getSource()), event.getValue()));
        };
    }
}

您可以在 [1] 找到示例实现。

• [0]https://docs.spring.io/spring-data/redis/docs/current/api/org/springframework/data/redis/core/RedisKeyExpiredEvent.html#getValue--
• [1]https://github.com/christophstrobl/next-level-redis-with-spring/blob/master/src/test/java/org/example/repository/RepsoitoryTests.java#L57