public boolean checkLogin(String username, String password) {
        Query query = em.createNamedQuery("Account.find");
        query.setParameter("username", username);
        query.setParameter("password", password);
        Account acc = (Account) query.getSingleResult();
        if (acc != null) {
            return true;
        } else {
            return false;
        }
    }


 String username = request.getParameter("txtUsername");
            String password = request.getParameter("txtPassword");
            HttpSession session = request.getSession();
            session.setAttribute("USER", username);
            session.setAttribute("PASS", password);
            try {
                Context context = new InitialContext();
                Object obj = context.lookup("luyentap1JNDI");
                luyentapSessionBeanRemote poji = (luyentapSessionBeanRemote) obj;
                boolean result = poji.checkLogin(username, password);
                String url ="loginerror.html";
                if(result){
                    boolean checkrole = poji.checkRoles(username);
                    if(checkrole){
                        url = "insert.jsp";
                    } else{
                        url = "roleerror.html";
                    }
                }
                RequestDispatcher rd = request.getRequestDispatcher(url);
                rd.forward(request, response);