[大数据]flink 报错is not serializable. The object probably contains or references non serializable fields.

今天有同事突然报了这样一个错误，刚开始确实没反应过来，成员变量不可以被序列化。。。。

Exception in thread "main" org.apache.flink.api.common.InvalidProgramException: java.lang.ref.ReferenceQueue$Lock@11fc564b is not serializable. The object probably contains or references non serializable fields.
	at org.apache.flink.api.java.ClosureCleaner.clean(ClosureCleaner.java:151)
	at org.apache.flink.api.java.ClosureCleaner.clean(ClosureCleaner.java:126)
	at org.apache.flink.api.java.ClosureCleaner.clean(ClosureCleaner.java:126)
	at org.apache.flink.api.java.ClosureCleaner.clean(ClosureCleaner.java:126)
	at org.apache.flink.api.java.ClosureCleaner.clean(ClosureCleaner.java:126)
	at org.apache.flink.api.java.ClosureCleaner.clean(ClosureCleaner.java:126)
	at org.apache.flink.api.java.ClosureCleaner.clean(ClosureCleaner.java:71)
	at org.apache.flink.streaming.api.environment.StreamExecutionEnvironment.clean(StreamExecutionEnvironment.java:1821)
	at org.apache.flink.streaming.api.datastream.DataStream.clean(DataStream.java:188)
	at org.apache.flink.streaming.api.datastream.KeyedStream.process(KeyedStream.java:398)
	at org.apache.flink.streaming.api.datastream.KeyedStream.process(KeyedStream.java:374)
	at com.xintujing.flinkdemo.text.UserCount_3.main(UserCount_3.java:53)
Caused by: java.io.NotSerializableException: java.lang.ref.ReferenceQueue$Lock
	at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1184)
	at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:348)
	at org.apache.flink.util.InstantiationUtil.serializeObject(InstantiationUtil.java:586)
	at org.apache.flink.api.java.ClosureCleaner.clean(ClosureCleaner.java:133)
	... 11 more

看到这个错，首先处于懵的状态，无法序列化，什么意思啊？

首先分析问题，他告诉我们某个类无法序列化了，

如果类中的一个成员未实现可序列化接口, 会发生什么情况？关于Java序列化过程的一个简单问题。如果尝试序列化实现可序列化的类的对象,但该对象包含对不可序列化类的引用,则在运行时将引发不可序列化异常 NotSerializableException,

是这样，如果你把一个对象作为另一个对象的成员变量，那么必须这个对象的所有成员变量都是可以被序列化的，如果成员变量不可以被序列化，那么就会报这个错误。所以。不要把不可序列化的东西当作成员变量就可以了啊。

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