liferay jsp如何取PorletSession的值

后台代码

  @Override  
        public void doView(RenderRequest renderRequest,RenderResponse renderResponse) throws IOException, PortletException {  
          String UsageUserID =  (String )renderRequest.getPortletSession().getAttribute("UsageUserID",PortletSession.APPLICATION_SCOPE);  
          System.out.println("PorletSessionB doView UsageUserID = " + UsageUserID);  
          renderRequest.setAttribute("UsageUserID", UsageUserID);  
          System.out.print("doview");
          super.doView(renderRequest, renderResponse);  
        }   

前台jsp

<%
String UsageUserID =  (String )renderRequest.getPortletSession().getAttribute("UsageUserID",PortletSession.APPLICATION_SCOPE);  
%>
UsageUserID = <%=UsageUserID %></br>