When to use Session Bean

Question

Good day fellas, I'm a confused about which session bean am to use for my application. I'm trying to build a mobile web app like Facebook which can allow multiple users at the same time. I surf the internet to get more information. From the info I gathered from stack overflow and other tutorials, is that a Stateful session beans maintain state both within and between transactions (conversational state) and that its meant for a client. Stateless does not but support multiple clients to pool the bean instance. Whilst Singleton is a little similar to Stateless bean.

My question is which session bean am I to use for the application. Thanks for your quick response.

NB: Client (Mobile phone) communicate with the servlet and the servlet communicates with EJB to pull data from the database.

public class LoginServlet extends HttpServlet {

@EJB
CampusianDataBaseBeanLocal campusianDataBaseBean;

Campusian campusian;
Gson gson;


@Override
public void init() throws ServletException {
    super.init();
    campusian = new Campusian();
    gson = new Gson();
}


/**
 * Processes requests for both HTTP
 * <code>GET</code> and
 * <code>POST</code> methods.
 *
 * @param request servlet request
 * @param response servlet response
 * @throws ServletException if a servlet-specific error occurs
 * @throws IOException if an I/O error occurs
 */
protected void processRequest(HttpServletRequest request, HttpServletResponse response)
        throws ServletException, IOException {
    response.setContentType("text/html;charset=UTF-8");
    PrintWriter out = response.getWriter();
    try {
        String username = request.getParameter("campusianUserName");
        String password = request.getParameter("campusianPassword");
        String gsonString;

        campusian.setUserName(username);
        campusian.setPassword(password);

        System.out.println("First time: "+username);

        /**
         * This check if the username and password entered by user is correct.
         * If yes set campusian setSuccess to true and convert the object to string using gson
         * Else set object campusian method to false
         */
        if (campusianDataBaseBean.login(campusian)) {
            campusian.setSuccess(true);
            System.out.println("Connected to the database");
            /**
            try {
                connection.connect();
                connection.login(username, password);
                if (connection.isAuthenticated()) {
                    System.out.println("Connected: "+connection.getServiceName());
                    campusian.setConnection(connection);
                    campusian.setSuccess(true);
                }else {
                    campusian.setSuccess(false);
                }
            } catch (XMPPException ex) {
                Logger.getLogger(LoginServlet.class.getName()).log(Level.SEVERE, null, ex);
            }
            **/
            gsonString = gson.toJson(campusian);
        }else {
            campusian.setSuccess(false);
            gsonString = gson.toJson(campusian);
        }

        //this sends the gson string to the mobile user
        out.print(gsonString);

    } finally {            
        out.close();
    }
}

}

Answer 1

You would need a singleton bean for all classes that do not preserve a state. In your case, for database communication, you need a singleton.

For user authentication, typically you store the user object or a user token somewhere in the session itself. Depending on your implementation you will have some kind of SessionContext/SessionStore where the login state is maintained.

You don't need session scoped beans for maintaining a user session!