How to set the portlet preference per user instead of global setting

Question

Hello All
I am using IBM JSR168/ JSF, In my portlet Edit mode I am trying to set a value per user preference , but it always set for all other users even this is just a normal user, I think when an administrator set any preference value then those preferences value will be set for all the users. but in my case it is a normal user has right for the edit mode and hence the preference set by the user in edit mode will be set for his portlet instance only. So why it sets for all the users preference???...... Thanks a lot for your help!!!
here is my code:
///////////portlet.xml//////////
<preference>
                    <name>RowsPerPage</name>
                    <value>25</value>
                    <read-only>false</read-only>
               </preference>/////////////////////////pageCode in edit mode do the save action/////////////////////////
public String doSaveAction(){     
           FacesContext ctx = FacesContext.getCurrentInstance();
              HttpSession session = (HttpSession)ctx.getExternalContext().getSession(false);
              if(session != null) {
                   session.setAttribute("save", "save");
                   session.setAttribute("Number",Integer.toString(getNumber()));
           return "";
}/////////////////////store the preference value///////
public class MyPortlet extends FacesGenericPortlet {
public void processAction(ActionRequest actionRequest, ActionResponse actionResponse) throws PortletException {
          try{               
            //String save1 = actionRequest.getParameter("save");
            String save = (String) actionRequest.getPortletSession().getAttribute("save");
            if (save != null){
               PortletPreferences prefs = actionRequest.getPreferences();
               String number= (String) actionRequest.getPortletSession().getAttribute("Number");
               prefs.setValue("Number", number);
               prefs.store();
          }

Answer 1

Hope someone really can help me for this issue... I just wondering is this related to the user group config in portlet, since the interesting is that this issue is not apply to wpsadmin , but not sure where and how to set other user group that can set the preference no problem??
Thanks for your time !