Redis獲取緩存異常：java.lang.ClassCastException: java.util.LinkedHashMap cannot be cast to XXX

Redis獲取緩存異常：java.lang.ClassCastException: java.util.LinkedHashMap cannot be cast to XXX。

出現這種異常，我需要自定義ObjectMapper，設置一些參數，而不是直接使用Jackson2JsonRedisSerializer類中黙認的ObjectMapper，看源代碼可以知道，Jackson2JsonRedisSerializer中的ObjectMapper是直接使用new ObjectMapper()創建的，這樣ObjectMapper會將Redis中的字符串反序列化為java.util.LinkedHashMap類型，導致后續Spring對其進行轉換成報錯。其實我們只要它返回Object類型就可以了。

使用以下方法，構建一個Jackson2JsonRedisSerializer對象，將其注入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);
        // 此項必須配置，否則會報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){
        //初始化一個RedisCacheWriter輸出流
        RedisCacheWriter redisCacheWriter = RedisCacheWriter.nonLockingRedisCacheWriter(connectionFactory);
        //采用Jackson2JsonRedisSerializer序列化機制

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

        //創建一個RedisSerializationContext.SerializationPair給定的適配器pair
        RedisSerializationContext.SerializationPair<Object> pair = RedisSerializationContext.SerializationPair.fromSerializer(jackson2JsonRedisSerializer());
        //創建CacheConfig
        RedisCacheConfiguration defaultCacheConfig = RedisCacheConfiguration.defaultCacheConfig().serializeValuesWith(pair);

        return new RedisCacheManager(redisCacheWriter, defaultCacheConfig);


    }