[Redis] ** cannot be cast to java.lang.String

先上問題：

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$sendTask.call(Unknown Source) at org.codehaus.groovy.runtime.callsite.CallSiteArray.defaultCall(CallSiteArray.java:48) at org.codehaus.groovy.runtime.callsite.AbstractCallSite.call(AbstractCallSite.java:113) at org.codehaus.groovy.runtime.callsite.AbstractCallSite.call(AbstractCallSite.java:125) at com.ppdai.realtime.datachannel.pullservice.dataproviders.bohai.BohaiQueryProvider.afterGetData(BohaiQueryProvider.groovy:395) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:498) at org.codehaus.groovy.runtime.callsite.PogoMetaMethodSite$PogoCachedMethodSiteNoUnwrapNoCoerce.invoke(PogoMetaMethodSite.java:210) at org.codehaus.groovy.runtime.callsite.PogoMetaMethodSite.callCurrent(PogoMetaMethodSite.java:59) at org.codehaus.groovy.runtime.callsite.CallSiteArray.defaultCallCurrent(CallSiteArray.java:52) at org.codehaus.groovy.runtime.callsite.AbstractCallSite.callCurrent(AbstractCallSite.java:154) at org.codehaus.groovy.runtime.callsite.AbstractCallSite.callCurrent(AbstractCallSite.java:166)

看問題緣由是序列化對象的時候使用的是 StringRedisSerializer, 原本覺得是由於AutoConfig 致使加載了系統默認的RedisTemplate， 而本身定義了RedisTemplate沒有加載，

可是很是疑惑的一點是默認的RedisTemplate使用的是 JdkSerializationRedisSerializer（以下代碼），上面異常報的是使用redis value 使用StringRedisSerializer 致使的類型轉化失敗

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; }

最後經過Alt + F7 (Find Usage) 發現下面這個代碼

private Long incr(String key, long delta){ RedisTemplate redisTemplate = getRedisTemplate() ValueOperations<String, String> operations = redisTemplate.opsForValue() redisTemplate.setKeySerializer(new StringRedisSerializer())  redisTemplate.setValueSerializer(new StringRedisSerializer()) return operations.increment(key, delta) }

原來就是這裏搞得鬼，將redisTemplate的ValueSerializer設置成了 StringRedisSerializer ，StringRedisSerializer參數是String類型的，所以就出現了類型轉化錯誤。

附說明

redisTemplate須要序列化key,value,hashkey,hashvalue,  提供了不少序列化工具，什麼Jackson、FastJson、JDKSerialization 也能夠本身定義。

redisTamplate默認這四種都使用JDKSerialization作序列化，若是沒有提供定義默認都用JDK。