XStream collection of type ad subtype

Question

I have classes like this:

class A{
//pojo
}
class B extends {
// pojo
}
class C{
@XStreamImplicit( itemFieldName="A")
private ArrayList<A> aList = null;
}

The filed aList of class C contains one object type of A.class and one type of B.class.

I can serialize and deserialize the class to this xml:

<c>
 <aList>
  <a/>
  <a/>
 </aList>
</c> 

But i want xml file to look like this:

<c>
 <aList>
  <a/>
  <b/>
 </aList>
</c> 

Is it possible? And how can I do it?

Answer 1

This works for me:

@XStreamAlias("a")
public class A {

}

@XStreamAlias("b")
public class B extends A {

}

@XStreamAlias("c")
public class C {
    private ArrayList<A> aList = null;

    public C() {
        aList = new ArrayList<A>();
        aList.add(new A());
        aList.add(new B());
        aList.add(new A());
    }

    public static void main(String[] args) {
        C c = new C();

        XStream x = new XStream();
        x.processAnnotations(A.class);
        x.processAnnotations(B.class);
        x.processAnnotations(C.class);

        System.out.println(x.toXML(c));
    }

}

and produce:

<c>
  <aList>
    <a/>
    <b/>
    <a/>
  </aList>
</c>

If you dont want to call processAnnotations for every possible class you can write some dynamic code using reflection API and process all classes in loop.