Problems with getting an Object from a table via the DataMod

[felle]

Hello I want to select an object from a Datatable via the DataModel and the DataModelSelectionIndex like in the booking example.
I always get an Exception :
....attempted to bind an Out attribute of the wrong type to: contributable...
My Class looks like this

@Stateful
@Name("findContributables")
@Interceptor(SeamInterceptor.class)
public class FindContributablesAction implements FindContributables, Serializable
{


 private static final long serialVersionUID = -6803933802941651662L;



 @PersistenceContext(type=EXTENDED)
 private EntityManager em;

 @DataModel
 private List<Object> contributables;
 @DataModelSelectionIndex
 private int contributableIndex;

 @Out
 private Object contributable;
 ....

and the method invoked in the Datatable is selectContributable()

 public String selectContributable()
 {
 if (contributables==null) return "contributableList";
 try{
 setContributable();
 }catch(Exception e){System.out.println(e+"@selectContributable");}
 System.out.println("Contributable was selected @setContributable");
 return "contributableSelected";
 }

 private void setContributable(){
 try{
 contributable = contributables.get(contributableIndex);
 }catch(Exception e){System.out.println(e.toString()+"@setContributable");}
 System.out.println("Contributable #"+contributableIndex+" was set @setContributable" +contributable.toString());
 }

The DataTable is generated by this method in the same class
The EntityManger return here a List of several Object form the type Journal ect.

 public List<Object> getAllContributables() {
 String[] types = {"Journal", "Book", "Workshop", "Conference"};
 List<Object> list = null;
 try {
 ContributableManager cm = new ContributableManagerBean(em);
 for (int i=0; i<types.length; i++) {
 List<Object> templist = cm.findContributable(types, null);
 if (list == null) {
 list = templist;
 }
 else {
 list.addAll(templist);
 }
 }
 }
 catch (Exception e) {
 }
 contributables = list;
 return list;
 }