portlet with velocity

[m.heidari@xxxxxxxxxxxxx]

hello,
I want to create a portlet with velocity and also i want to use Exo 
UIComponent such as JSFLink or JSFButton.if anyone has an example or tutorial 
about this please help me.
i use some project in exo such as exo-portal.portlets.web.
for example in the following class the uicomp can't set correctly and 
nodeTypeForm  set by null.

static public class ViewActionListener extends ExoActionListener {
    public void execute(ExoActionEvent event) throws Exception {
      UINodeTypeList uicomp = (UINodeTypeList) event.getComponent() ;
      String nodeName = event.getParameter(OBJECTID) ;
      NodeType nodeType = uicomp.ntManager_.getNodeType(nodeName) ;
      UINodeTypeForm nodeTypeForm = 
(UINodeTypeForm)uicomp.getSibling(UINodeTypeForm.class) ;      
      String[] namespaces = 
uicomp.repository_.getNamespaceRegistry().getPrefixes() ;      
      nodeTypeForm.update(uicomp.session_, nodeType, uicomp.ntManager_, 
namespaces, true) ;      
      uicomp.setRenderedSibling(UINodeTypeForm.class) ;
    }
  }
 
thanks
m.heidari