Redis 自定义对象 cannot be cast to java.lang.String

Redis序列化对象的时候报错如下

java.lang.ClassCastException: com.ppdai.cbd.ddp.thirdparty.contract.bhxtzx.BHXTZXTask cannot be cast to java.lang.String
        at org.springframework.data.redis.serializer.StringRedisSerializer.serialize(StringRedisSerializer.java:33)
        at org.springframework.data.redis.core.AbstractOperations.rawValue(AbstractOperations.java:117)
        at org.springframework.data.redis.core.DefaultListOperations.leftPush(DefaultListOperations.java:71)
        at org.springframework.data.redis.core.DefaultBoundListOperations.leftPush(DefaultBoundListOperations.java:60)
        at com.ppdai.realtime.datachannel.pullservice.entity.RedisQueue.pushFromHead(RedisQueue.java:63)
        at com.ppdai.realtime.datachannel.pullservice.redisconfig.RedisTaskSender.sendTask(RedisTaskSender.java:35)
        at com.ppdai.realtime.datachannel.pullservice.redisconfig.RedisTaskSender$sendTask.call(Unknown Source)
        at org.codehaus.groovy.runtime.callsite.CallSiteArray.defaultCall(CallSiteArray.java:48)
        at org.codehaus.groovy.runtime.callsite.AbstractCallSite.call(AbstractCallSite.java:113)
        at org.codehaus.groovy.runtime.callsite.AbstractCallSite.call(AbstractCallSite.java:125)

BHXTZXTask是自己定义的Bean，因此问题就变成了自定义的对象不能转成String对象，为什么会需要转成String对象呢

因为redis默认使用jdkSerializer，看RedisTemplate的代码如下，

afterPropertiesSet函数

public class RedisTemplate<K, V> extends RedisAccessor implements RedisOperations<K, V>, BeanClassLoaderAware {

    public void afterPropertiesSet() {

        super.afterPropertiesSet();

        boolean defaultUsed = false;

        if (defaultSerializer == null) {

            defaultSerializer = new JdkSerializationRedisSerializer(
                    classLoader != null ? classLoader : this.getClass().getClassLoader());
        }

        if (enableDefaultSerializer) {

            if (keySerializer == null) {
                keySerializer = defaultSerializer;
                defaultUsed = true;
            }
            if (valueSerializer == null) {
                valueSerializer = defaultSerializer;
                defaultUsed = true;
            }
            if (hashKeySerializer == null) {
                hashKeySerializer = defaultSerializer;
                defaultUsed = true;
            }
            if (hashValueSerializer == null) {
                hashValueSerializer = defaultSerializer;
                defaultUsed = true;
            }
        }

        if (enableDefaultSerializer && defaultUsed) {
            Assert.notNull(defaultSerializer, "default serializer null and not all serializers initialized");
        }

        if (scriptExecutor == null) {
            this.scriptExecutor = new DefaultScriptExecutor<K>(this);
        }

        initialized = true;
    }
}

查看源码，如下，通过rawValue()函数获取序列化之后的字节码

public Long leftPush(K key, V value) {
        final byte[] rawKey = rawKey(key);
        final byte[] rawValue = rawValue(value);
        return execute(new RedisCallback<Long>() {

            public Long doInRedis(RedisConnection connection) {
                return connection.lPush(rawKey, rawValue);
            }
        }, true);
    }

private byte[] rawValue(Object value) {
   if (valueSerializer == null && value instanceof byte[]) {
      return (byte[]) value;
   }
   return valueSerializer.serialize(value);
}

通过 valueSerializer序列化来序列化对象, redis如果不配置，默认 valueSerializer的序列化是会使用

StringRedisSerializer stringRedisSerializer = new StringRedisSerializer();
        JdkSerializationRedisSerializer jdkSerializationRedisSerializer = new JdkSerializationRedisSerializer();

        System.out.println(redisTemplate.hasKey("bohai_credit"));
        redisTemplate.delete("bohai_credit");

        System.out.println(stringRedisSerializer.serialize("bohai_credit"));
        System.out.println(jdkSerializationRedisSerializer.serialize("bohai_credit"));