Fixing Serialization bug in evolved class

Question

I've been assigned to fix a bug related to Serialization and class evolution.
We have a class UserKey that is serializable and has gone through a couple of revisions.
Revision 1 of the class looks like this:
public class UserKey implements Serializable
    static final long serialVersionUID = 8034873336L;
    private byte position = 0;
    private byte day = 0;
    private byte month = 0
    private short year = 0;
    private int key = 0;
    <snip>
}In revision 2 of the class another data member was added:
   private string keyName;serialVersionUID was left unchanged.
Revisions 1 and 2 have been released and have been in use for quite some time. Now I am supposed to make a revision 3 that can deserialize data that was serialized from either rev 1 or 2 of the class. Is this possible?

Answer 1

Ok, I've added this and it seems to work:
    private void readObject(ObjectInputStream ois)
        throws ClassNotFoundException, IOException
        try
            ois.defaultReadObject();
            if (keyName == null)
                keyName = "";
        catch (ClassNotFoundException ex)
            ex.printStackTrace();
        catch (IOException ex)
            ex.printStackTrace();
    }Can it really be that simple?