We want to use @Cacheable in Spring Boot with redis, and we want the redis content to be JSON so it is human readable.

This is done in our CacheConfiguration with

@Autowired
public CacheConfiguration(ObjectMapper objectMapper) {
    // we need to modify the default objectMapper for redis so make a copy
    this.objectMapper = objectMapper.copy()
        .activateDefaultTyping(
             objectMapper.getPolymorphicTypeValidator(),
             ObjectMapper.DefaultTyping.NON_FINAL,
            JsonTypeInfo.As.PROPERTY
         );

}

@Bean
public RedisCacheManagerBuilderCustomizer redisCacheManagerBuilderCustomizer() {
    RedisSerializer<Object> serializer = new GenericJackson2JsonRedisSerializer(objectMapper);

    return (builder) -> builder
       .withCacheConfiguration(DEFAULT_CACHE,
            RedisCacheConfiguration.defaultCacheConfig()
                .entryTtl(Duration.ofMinutes(60))
                .serializeValuesWith(RedisSerializationContext.SerializationPair.fromSerializer(serializer))
    );

}

This adds the “@class” property to the JSON so that it can be deserialized. However, it also changes how BigDecimal is serialized. BigDecimal values become this in the JSON

  "someBigDecimalProperty" : [ "java.math.BigDecimal", 11.25 ],

which looks sane enough, however it fails when fetched from the cache and is deserialized (presumably by the same ObjectMapper).

We get

[org.springframework.web.servlet.mvc.method.annotation.ExceptionHandlerExceptionResolver] Resolved [org.springframework.data.redis.serializer.SerializationException: Could not read JSON:Cannot deserialize value of type java.lang.String from Array value (token JsonToken.START_ARRAY) at [Source: (byte[])”{ “@class” : “com.mycompany.model.dto.MyObject”, “someBigDecimalProperty” : [ “java.math.BigDecimal”, 11.25 ], column: 26] (through reference chain: com.mycompany.model.dto.MyObject[“someBigDecimalProperty”]) ]

Why can it not deserialize what it serializes? Am I missing something in the configuration?