PropertyModel/TextArea keeps reference to my detached object!

[Wayne Pope]

Ok,

this has take me ages to figure out what is happening.
I have a model that represents a hibernate entity (called Document). I have
a form with a couple of fields which uses PropertyModel on the model and I
set the model on this forms contructor.ie.:

setModel(model);
add(new TextField("title", new
PropertyModel(getModelObject(),"latestVersion.title")));
add(new TextArea("quicksummary", new
PropertyModel(getModelObject(),"latestVersion.summary")));

this model is :
public class DocumentModel extends Model {

    Document doc;
    Long id;

    public DocumentModel() {
    }

    public DocumentModel(Long docId) {
        id = docId;
    }

    @Override
    public Object getObject() {
        if (doc != null)
            return doc;
        if (id == null) {
            doc = new Document();
        } else {
            doc =
DAOFactory.getFactory().getDocumentDAO().findByPrimaryKey(id);
        }
        return doc;
    }

    @Override
    public void setObject(Object obj) {
        doc = (Document)obj;
        id = (doc == null) ? null : doc.getId();
    }

    @Override
    public void detach() {
        doc = null;
    }

}

When the constructor for the form is called I see that the PropertyModel
gets the Document entity from my model and populates the fields. My
DocumentModel is detached and page displayed. So far far so good.

However when the form is submitted, I see that during the Form validation
the method TextArea,setModelObject is calling model.setObject(object). (The
model here is the PropertyModel class instance that was contructed in my
forms constructor) - I see that this has a reference to my detached Document
entity.
THe problems is that in my onSubmit method which is called after the above
validation etc, is when I call getModelObject() it in turns calls
getObject() which (as its detached) loads the entity again from the database
- however this is a different object to the one PropertyModels updated!!!!

So the PropertyModel's are updating an object that was detached!

So plainly I don;t understand what I'm ment to do with Wicket and detached
models - how to you have a form that represents an entity and make it
detached?
Thanks
Wayne