How to get number of connected users and their role using j_security_check?

Question

I get the username of the connected user (using j_security_check) this way, through a managed bean:

......
    username =   FacesContext.getCurrentInstance().getExternalContext().getUserPrincipal().getName();

And then display it in a jsf page this way : #{userBean.username} But I figured no way to get the number of connected users and get their role. In other words, I want to display besides the username, the user role and the number of connected users. How can I achieve this!? Thanks in advance for your help!

EDIT: I can now get the Role of the connected user, using a namedquery in a managed bean :

public Users getUserRole(){
      try {
            Users auser = (Users)
            em.createNamedQuery("Users.findByUsername").
                    setParameter("username", getRemoteUser()).getSingleResult();
            return auser; 
        } catch (NoResultException nre) {
            JsfUtil.addErrorMessage(nre, "getUserRole Error");
            return null;
        }

    }

and in the xhtml page:

<h:outputLabel for="rolefacet" value="Role: "/>
  <h:outputFormat id="rolefacet" value="#{UserBean.userRole.ugroup}" /> 

while ugroup is the role name in the Users entity class.

---

EDIT: One solution that still does not work for me is to add a HttpSessionListener to my web.xml:

package beans;

/**
 *
 * @author med81
 */

import java.io.Serializable;
import javax.servlet.http.HttpSessionEvent;
import javax.servlet.http.HttpSessionListener;
import javax.servlet.http.HttpSession;
import java.util.List;
import java.util.ArrayList;

import javax.faces.context.FacesContext;


public class SessionCounter implements Serializable, HttpSessionListener {

    private List sessions = new ArrayList();
   Object  s =  FacesContext.getCurrentInstance().getExternalContext().getSession(false);

    public Object getS() {
        return s;
    }

    public void setS(Object s) {
        this.s = s;
    }


    public SessionCounter() {
    }


    public void sessionCreated(HttpSessionEvent event) {
        HttpSession session = event.getSession();
        sessions.add(session.getId());

        session.setAttribute("counter", this);
    }


    public void sessionDestroyed(HttpSessionEvent event) {
        HttpSession session = event.getSession();
        sessions.remove(session.getId());

        session.setAttribute("counter", this);
    }

    /**
     * 
     * @return size of the session list
     */
    public int getActiveSessionNumber() {
        return sessions.size();
    }


}

Answer 1

get the number of connected users

I'll assume that you mean to get the number of logged-in users.

Basically, you need to have an applicationwide Set<User> with all logged-in users and add the User to it when it logs in and remove the User when it logs out or when its session is destroyed. Here's an example which uses an application scoped managed bean

@ManagedBean(eager=true)
@ApplicationScoped
public class LoginManager implements Serializable {

    private Set<User> users = new HashSet<User>();

    public Set<User> getUsers() {
        return users;
    }

}

If you were using Java EE 6 it would have been easy to replace j_security_check by a managed bean method which utilizes the new Servlet 3.0 HttpServletRequest#login() and simultaneously adds the User to the Set<User> of the injected LoginManager bean. But on Java EE 5 there is no trivial way to hook on it. You would need to check every request for the logged-in user. Best to achieve this is to put the User object in the session whenever there's an UserPrincipal. You can do this using a filter which does roughly the following job in doFilter() method.

UserPrincipal principal = request.getUserPrincipal();
User user = (User) session.getAttribute("user");

if (principal != null && user == null) {
    user = userService.findByName(principal.getName());
    session.setAttribute("user", user);
    LoginManager loginManager = (LoginManager) servletContext.getAttribute("loginManager");
    loginManager.getUsers().add(user);
}

Finally, to remove the user from the logins, best is to hook on HttpSessionListener#sessionDestroyed(), assuming that you're invalidating the session on logout. This will also be called when the session expires.

public void sessionDestroyed(HttpSessionEvent event) {
    User user = (User) event.getSession().getAttribute("user");
    if (user != null) {
        LoginManager loginManager = (LoginManager) event.getSession().getServletContext().getAttribute("loginManager");
        loginManager.getUsers().remove(user);
    }
}