java序列化异常：Caused by: java.io.NotSerializableException: java.security.ProtectionDomain

在运行时突然报序列化异常

Exception in thread "main" java.lang.reflect.InvocationTargetException
	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 com.intellij.rt.execution.CommandLineWrapper.main(CommandLineWrapper.java:63)
Caused by: org.apache.flink.api.common.InvalidProgramException: [Ljava.security.ProtectionDomain;@2575f671 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: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:1852)
	at org.apache.flink.streaming.api.datastream.DataStream.clean(DataStream.java:195)
	at org.apache.flink.streaming.api.datastream.DataStream.map(DataStream.java:608)
	at com.hll.zhgk.jobs.NewAqjkxtConfigSensorInfoJobs.main(NewAqjkxtConfigSensorInfoJobs.java:61)
	... 5 more
Caused by: java.io.NotSerializableException: java.security.ProtectionDomain
	at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1184)
	at java.io.ObjectOutputStream.writeArray(ObjectOutputStream.java:1378)
	at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1174)
	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)
	... 18 more

Process finished with exit code 1

问题解决1：常见的处理方式是该类或者该类中的调用类或者变量不能被序列化导致的。

• 1：类序列化。类实现接口即可 implements Serializable
• 2：变量没有别序列化。重点：资源类的变量无法被序列化。比如hadoop,hbase的Configuration conf资源
  在类中直接使用时就会报序列化异常，此时用transient 关键字修饰变量即可正常运行。
• 3：对于资源类型的变量不想使用transient关键字的，如果是全局变量也可以使用static静态关键字进行修饰，被static修饰过的也不会被序列化和反序列化。

我的属于资源变量无法被初始化，使用以下两种之一进行解决均可。

 private  static Connection conn = null;  			//static静态关键字
 private  transient Connection conn = null;         //transient 关键字

在序列化中不仅保留当前类的对象的数据，而且递归保存对象引用的每一个对象的数据。将整个对象层次写入字节流中，这也就是序列化对象的“深复制”，即复制对象本身及引用对象本身；（深拷贝和浅拷贝面试重点）

1：无法别序列化的：

方法；
有static修饰的属性；
有transient修饰的属性

transient关键字：
将不需要序列化的属性前添加关键字transient，序列化对象的时候，这个属性就不会被序列化。