Preserving references to objects across stream items

Hi,

I'm rather new to XStream. The library's great, but I still have a problem I cannot solve. I couldn't find an answer in the docs, nor in the mailing list.

I have two objects p1 and p2. p2 contains a reference to p1. If I put them both in a list and serialize the list, everything's ok. If I try to serialize them one after the other, I get duplicates.

Is this OK, and I'm missing something?

Thank you very much.
Francesco

File Person.java:
------------------------------------------
import java.io.*;

public class Person implements Serializable
{
Person(String n, int a, Person s)

{ name = n; age = a; secretary = s; }

public String name;
public int age;
public Person secretary;
}
------------------------------------------

File TestMultipleRefs.java
------------------------------------------
import java.util.*;
import java.io.*;

import com.thoughtworks.xstream.*;
import com.thoughtworks.xstream.io.xml.*;

public class TestMultipleRefs
{
public static void main(String[] args)
{
Person p1;
Person p2;

p1 = new Person("Alice", 50, null);
p2 = new Person("Joe", 35, p1);

ArrayList list = new ArrayList();
list.add(p1);
list.add(p2);

// Serialize
XStream xstream = new XStream(new DomDriver());
java.io.StringWriter writer = new java.io.StringWriter();
try

{ ObjectOutputStream out = xstream.createObjectOutputStream(writer); // ObjectOutputStream out = // new ObjectOutputStream(new FileOutputStream("test.dat")); out.writeObject(p1); out.writeObject(p2); out.writeObject(list); out.close(); }

catch (IOException e)

{e.printStackTrace();}

// Write down XML
System.out.println(writer.toString());

// Deserialize
java.io.StringReader reader = new java.io.StringReader(writer.toString());
try
{ ObjectInputStream in = xstream.createObjectInputStream(reader); // ObjectInputStream in = // new ObjectInputStream(new FileInputStream("prova.dat")); p1 = (Person)in.readObject(); p2 = (Person)in.readObject(); list = (ArrayList)in.readObject(); in.close(); }
catch (IOException e) {e.printStackTrace();}

catch (ClassNotFoundException e)

{e.printStackTrace();}

Person p1List = (Person) list.get(0);
Person p2List = (Person) list.get(1);
p1.age=25;
System.out.println("Alice's age: "+p1.age);
System.out.println("Age of Joe's secretary: "+p2.secretary.age);
p1List.age = 35;
System.out.println("Alice's age: "+p1List.age);
System.out.println("Age of Joe's secretary: "+p2List.secretary.age);
}
}