AWS Elasticache using Lettuce: Date fields are not getting fetched correctly

[alekhya538]

Hello there!

I am using Lettuce java client to talk to AWS Elasticache (Valkey cache using serverless, IAM authentication).

Below is the code for writing to cache & reading from cache:

     public void writeToCache(String key, Object value, long ttl) {
        log.info("Writing to Cache with key:{} ttl:{} value:{}", key, ttl, value);

        cacheAsyncConnectionPool.thenCompose(connectionPool -> {
            try {
                StatefulRedisConnection<String, String> connection = connectionPool.acquire().get();
                RedisAsyncCommands<String, String> async = connection.async();
                async.jsonSet(key, JsonPath.ROOT_PATH, async.getJsonParser().fromObject(value));
                async.expire(key, ttl);
                return async.exec().whenComplete((s, throwable) -> connectionPool.release(connection));
            } catch (Exception e) {
                log.warn("Exception while writing to Cache -  e: {}", e);
                return null;
            }
        });
    }

    public Object readFromCache(String key) {
        log.info("Reading from cache for key: {}", key);

        final JsonValue[] value = {null};
        cacheAsyncConnectionPool.thenCompose(connectionPool -> {
            try {
                StatefulRedisConnection<String, String> connection = connectionPool.acquire().get();
                RedisAsyncCommands<String, String> async = connection.async();
                List<JsonValue> jsonList = async.jsonGet(key, JsonPath.ROOT_PATH).get();
                value[0] = jsonList.get(0).asJsonArray().get(0);
                return async.exec().whenComplete((s, throwable) -> connectionPool.release(connection));
            } catch (Exception e) {
                log.warn("Exception while reading from Cache - e: {}", e.getLocalizedMessage());
                return null;
            }
        });
        return value[0].toObject(Object.class);
    }

Problem is when I store json containing date fields in the cache, they are returned in a different format.

Write to Cache -
{
"startDate": "2021-06-17T00:00:00.000+00:00",
"endDate": "2025-04-29T23:59:59.000+00:00"
}

Read from cache -

{
"startDate": 1623888000000,
"endDate": 1745971199000
}

How can I make the date fields to be stored in the same format ?

Regards,
Alex

[tishun]

Hey @alekhya538 ,

can we also see the model class definition?

I assume that Object.class is a placeholder? Or do you use this exact code?

        return value[0].toObject(Object.class);

[tishun]

Depending on how you handle dates in your application and what object you map the JSON to you might need to do some additional work. In the most simple case you can just do the following:

The model class, using a public Date field:

   class MountainBike {

        public Date lastServiced;

    }

Writing the value to the Redis server :

        JsonPath myPath = JsonPath.of("$..mountain_bikes[1]");
        JsonParser parser = redis.getJsonParser();
        Date theDate = new Date(Instant.now().toEpochMilli());

        MountainBike desertFox = new MountainBike();
        desertFox.lastServiced = theDate;

        JsonValue newValue = parser.fromObject(desertFox);

        String result = redis.jsonSet(BIKES_INVENTORY, myPath, newValue);
 
        JsonValue value = redis.jsonGet(BIKES_INVENTORY, myPath).get(0);

        MountainBike newBike = value.asJsonArray().get(0).asJsonObject().toObject(MountainBike.class);
        assertThat(newBike.lastServiced).isEqualTo(theDate);
        assertThat(result).isEqualTo("OK");

For more details on how you can handle dates in a more robust way than using timestamps please consult the documentation, for example https://www.baeldung.com/jackson-serialize-dates

[alekhya538]

Thanks @tishun

I resolved it by using @DateTimeFormat annotation in my model class.

    @JsonProperty("startDate")
    @DateTimeFormat(iso = DateTimeFormat.ISO.DATE_TIME)
    private Date startDate;

[tishun]

Happy to help!