序列化中的版本兼容问题

package tigers;

import java.io.*;

public class Tiger5 {
static class Inner implements Serializable {
private String name;
public Inner(String name) {
this.name = name;
}
public String toString() {
return "Tiger5$Inner:(" + name + ")";
}
//public void todo() {}
}
private static void writeObject(Inner in) throws IOException {
ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream("Tiger5$Inner.tmp"));
oos.writeObject(in);
}
private static Inner readObject() throws IOException, ClassNotFoundException {
ObjectInputStream ois = new ObjectInputStream(new FileInputStream("Tiger5$Inner.tmp"));
return (Inner) ois.readObject();
}
public static void main(String[] args) {
Inner in = new Inner("inner");
try {
writeObject(in);
//in = readObject();
System.out.println(in);
} catch (Exception e) {
e.printStackTrace();
}
}
}

结果：

老版本的Inner对象被序列化到Tiger5$Inner.tmp文件中。

现在，在Inner中增加一个简单的非私有的todo()方法：

public void todo(){}

并修改main()方法如下，以便用新版本Inner类进行反序列化：

try {
//writeObject(in);
in = readObject();
System.out.println(in);
} catch (Exception e) {
e.printStackTrace();
}

结果：

java.io.InvalidClassException: tigers.Tiger5$Inner; local class incompatible: stream classdesc serialVersionUID = 925364839964073665, local class serialVersionUID = 2692111289122516972
at java.io.ObjectStreamClass.initNonProxy(ObjectStreamClass.java:519)
at java.io.ObjectInputStream.readNonProxyDesc(ObjectInputStream.java:1546)
at java.io.ObjectInputStream.readClassDesc(ObjectInputStream.java:1460)
at java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:1693)
at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1299)
at java.io.ObjectInputStream.readObject(ObjectInputStream.java:339)
at tigers.Tiger5.readObject(Tiger5.java:34)
at tigers.Tiger5.main(Tiger5.java:40)

现在在Inner中加入版本控制字段：

private static final long serialVersionUID = 0;

然后按上面的步骤将老版本Inner对象序列化，并用新版本Inner对象读取，发现可以成功读取。