Java – deserialization version conflict

My question is, what is a good way to upgrade obsolete objects?

For example, suppose you have a class like this:

public class Foo() implements Serializable {
    int a;
    String b;
}

Then you serialize the object You can then add more features to your course by adding the following:

...
int c;
...

You still want to keep the information in the serialized object, but I know there will be a conflict if you try to deserialize it Is there any way (perhaps by checking serialVersionUID) to set a value for int c that knows it does not exist?

thank you

Solution

You need to add a private method:

private void readObject(ObjectInputStream ois) {
      // compare serialVersionUID and determine which fields to expect
      // read the expected fields for that version
      // initialize the new fields.
    }

For more information, read serialization specs