add user with Struts

Hi !

I wish to create a new user trough a sample Form with Struts. I've got a 
text field for the new user name and then I call the Slide API.

Here is my code AddUserAction : 

    public ActionForward execute(ActionMapping mapping, ActionForm form, 
HttpServletRequest request, HttpServletResponse response) throws Exception 
{
        String username = ((demo.AddUserForm)form).getUsername();
 
        // prepare the namespace access token (assuming you want the 
default namespace)
        String namespace = Domain.getDefaultNamespace();
 
        SlideToken st = WebdavUtils.getSlideToken(request);
 
        if(!"".equals(username)) {
                NamespaceAccessToken nat = Domain.accessNamespace(new 
SecurityToken(this), namespace);
                // prepare the structure helper
                Structure structureHelper = nat.getStructureHelper();

                try {
                        try {
                                // start namespace tansaction
                                nat.begin();
                                // retrieve the node to be linked
                                SubjectNode user = new SubjectNode(
USERS_REPOSITORY + username);
 
                                structureHelper.create(st, user, 
USERS_REPOSITORY + username);
                                // commit the transaction
                                nat.commit();
                        } catch (AccessDeniedException ex) {
                                ex.printStackTrace();
                                throw ex;
                        } catch (ObjectAlreadyExistsException ex) {
                                ex.printStackTrace();
                                throw ex;
                        } catch (Exception ex) {
                                ex.printStackTrace();
                                throw ex;
                        }
                        // ... SUCCESS ...
                } catch (Exception ex) {
                        try {
                                nat.rollback();
                        } catch (SystemException sysex) { // catch 
silently }

                        }
                }
        }

 
      return mapping.findForward(FORWARD_addUser);
    }

But the security check fails (I've added some logs in LTISecurityImpl that 
inherits from ACLSecurityImpl) :

Check credentials on /users by /users/root for action /actions/bind
Check credentials on /users by /users/root for action /actions/write  (--> 
this is to store the parent object)
Check credentials on /users/johnny by /users/root for action 
/actions/write
org.apache.slide.security.AccessDeniedException: Access denied on 
/users/johnny by user /users/root for action /actions/write
        at org.apache.slide.security.SecurityImpl.checkCredentials(
SecurityImpl.java:427)
        at fr.lti.magic.LTISecurityImpl.checkCredentials(
LTISecurityImpl.java:21)
        at org.apache.slide.structure.StructureImpl.store(
StructureImpl.java:488)
        at org.apache.slide.structure.StructureImpl.store(
StructureImpl.java:458)
        at org.apache.slide.structure.StructureImpl.create(
StructureImpl.java:380)
        at demo.AddUserAction.createUser(AddUserAction.java:80)

From what I understand, the parent object is first stored (here /users) to 
reflect the new added child and then the child is stored. But to store the 
child (here /users/jonnhy), Slide first checks if root has write access on 
/users/johnny ! There is obviously something wrong, but I don't get it.

Thanks for your help !
Jean-Damien Bouvier