String password = request.getParameter("password");
url = "/usuarios/jsp/login.jsp";
if (username != null && password != null) {
Manager m = Manager.getInstace();
Usuario u = null;
u = m.login(username, password);
if (u == null) {
msg = "Usuario e/ou senha invalidos! Tente novamente.";
} else {
request.getSession().setAttribute("usuario", u);
url = "/usuarios/jsp/welcome.jsp";