Spring-data-redis @Cacheable java.lang.ClassCastException: java.util.LinkedHashMap cannot be cast to MyObject

Question

I am using spring-data-redis for caching data in my spring boot app. I am using Mongo as my primary data source and Redis as a cache. When I hit the API for the first time, it fetches record from Mongo and saves it in Cache, and returns MyObject correctly to the client. But when I hit the API second time, it finds the record in the Cache, and while trying to deserialize that back into MyObject, it . always runs into a cast exception:

java.lang.ClassCastException: java.util.LinkedHashMap cannot be cast to MyObject

Here is my Redis Configuration:

public class MyConfiguration {
    @Bean
    public CacheManager cacheManager(RedisTemplate<String, MyObject> redisTemplate) {
        return new RedisCacheManager(redisTemplate);
    }

    @Bean
    public RedisTemplate<String, MyObject> redisTemplate(RedisConnectionFactory connectionFactory, ObjectMapper objectMapper) {
        StringRedisSerializer serializer = new StringRedisSerializer();
        GenericJackson2JsonRedisSerializer hashValueSerializer = new GenericJackson2JsonRedisSerializer(objectMapper);
        RedisTemplate<String, MyObject> redisTemplate = new RedisTemplate<>();
        redisTemplate.setKeySerializer(serializer);
        redisTemplate.setValueSerializer(hashValueSerializer);
        redisTemplate.setConnectionFactory(connectionFactory);
        return redisTemplate;
    }
}

Found same problem reported here: Spring-data-redis @Cacheable java.lang.ClassCastException: java.util.HashMap cannot be cast to java.lang.String

I researched for quite some time but have no ideas. Please suggest. Thanks a ton in advance.

Answer 1

It worked for me by simply setting a new GenericJackson2JsonRedisSerializer() with no arguments, in both Key, value serializer and hash key, value serializer

@Bean
    public RedisTemplate<String, Object> redisTemplate(LettuceConnectionFactory lettuceConnectionFactory, ObjectMapper objectMapper) {
        final RedisTemplate<String, Object> redisTemplate = new RedisTemplate<String, Object>();
        redisTemplate.setConnectionFactory(lettuceConnectionFactory);
        // value serializer
        redisTemplate.setKeySerializer(new StringRedisSerializer());
        redisTemplate.setValueSerializer(new GenericJackson2JsonRedisSerializer());
        // hash value serializer
        redisTemplate.setHashKeySerializer(new StringRedisSerializer());
        redisTemplate.setHashValueSerializer(new GenericJackson2JsonRedisSerializer());

        logger.info("wiring up Redistemplate...");
        return redisTemplate;
    }