Redis获取缓存异常：java.lang.ClassCastException: java.util.LinkedHashMap cannot be cast to XXX

Redis获取缓存异常：java.lang.ClassCastException: java.util.LinkedHashMap cannot be cast to XXX。

出现这种异常，我需要自定义ObjectMapper，设置一些参数，而不是直接使用Jackson2JsonRedisSerializer类中黙认的ObjectMapper，看源代码可以知道，Jackson2JsonRedisSerializer中的ObjectMapper是直接使用new ObjectMapper()创建的，这样ObjectMapper会将Redis中的字符串反序列化为java.util.LinkedHashMap类型，导致后续Spring对其进行转换成报错。其实我们只要它返回Object类型就可以了。

使用以下方法，构建一个Jackson2JsonRedisSerializer对象，将其注入RedisCacheConfiguration即可。

 private Jackson2JsonRedisSerializer<Object> jackson2JsonRedisSerializer() {
        Jackson2JsonRedisSerializer<Object> jackson2JsonRedisSerializer =
                new Jackson2JsonRedisSerializer<>(Object.class);
        ObjectMapper objectMapper = new ObjectMapper();
        objectMapper.setVisibility(PropertyAccessor.ALL, JsonAutoDetect.Visibility.ANY);
        objectMapper.configure(MapperFeature.USE_ANNOTATIONS, false);
        objectMapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);
        objectMapper.configure(SerializationFeature.FAIL_ON_EMPTY_BEANS, false);
        // 此项必须配置，否则会报java.lang.ClassCastException: java.util.LinkedHashMap cannot be cast to XXX
        objectMapper.enableDefaultTyping(ObjectMapper.DefaultTyping.NON_FINAL, JsonTypeInfo.As.PROPERTY);
        objectMapper.setSerializationInclusion(JsonInclude.Include.NON_NULL);
        jackson2JsonRedisSerializer.setObjectMapper(objectMapper);
        return jackson2JsonRedisSerializer;
    }

    @Bean
    public RedisCacheManager redisCacheManager(RedisConnectionFactory connectionFactory){
        //初始化一个RedisCacheWriter输出流
        RedisCacheWriter redisCacheWriter = RedisCacheWriter.nonLockingRedisCacheWriter(connectionFactory);
        //采用Jackson2JsonRedisSerializer序列化机制

//        Jackson2JsonRedisSerializer<Object> serializer = new Jackson2JsonRedisSerializer<Object>(Object.class);

        //创建一个RedisSerializationContext.SerializationPair给定的适配器pair
        RedisSerializationContext.SerializationPair<Object> pair = RedisSerializationContext.SerializationPair.fromSerializer(jackson2JsonRedisSerializer());
        //创建CacheConfig
        RedisCacheConfiguration defaultCacheConfig = RedisCacheConfiguration.defaultCacheConfig().serializeValuesWith(pair);

        return new RedisCacheManager(redisCacheWriter, defaultCacheConfig);


    }