Without diving too deep in the subject I would like to add that one could also use the
Externalizable interface instead of Serializable. This interface extends
the java.io.Serializable interface and adds two methods :

public void writeExternal(ObjectOutput out)
public void readExternal(ObjectInput in)

These methods are automatically called during serialization and de-serialization.
Therefore, by providing code for these methods, you can implement your own serialization-specific
operations, and, thus, have control over what data to, or not to serialize.

As a result using the Externalizable interface will provide you fine grained control
over the object which you would like to migrate to a newer version of a class.