Deserialize a transient member of an object to a non-null default in Java

Question

public class MyObj implements Serializable {
  private transient Map myHash = new HashMap();
  ...
}

Is

Answer 1

public class MyObj implements Serializable {
    private transient Map<String, Object> myHash = new HashMap<String, Object>();

    private void readObject(ObjectInputStream in) throws IOException, ClassNotFoundException {
        in.defaultReadObject();

        myHash = new HashMap<String, Object>();
    }
}

Answer 2

What about adding a readObject method like this:

public class MyObj implements Serializable {
  private transient Map<String, Object> myHash = new HashMap<String, Object>();
  ...
  private void readObject(ObjectInputStream in) throws IOException, ClassNotFoundException {
    in.defaultReadObject();     
    myHash = new HashMap<String, Object>();
  }
}

That should sort you out.

Answer 3

You can implement your own custom readIn method and explicitly create a new Map<T> as explained in the Java Serializable documentation. That article should describe how to do what you're looking for; check the section entitled Customize the Default Protocol.