@WebServlet("/login")
public class LoginServlet extends HttpServlet {

  @Override
  protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    response.setContentType("text/html");
    response.setCharacterEncoding("UTF-8");

    String username = request.getParameter("username");
    String password = request.getParameter("password");

    try {
      Database.connect();
      User user = Database.jdbi.withExtension(UserDao.class,
        dao -> dao.getUser(username, password));
      if (user != null) {
        HttpSession session = request.getSession();
        session.setAttribute("username", user.getUsername());
        session.setAttribute("role", user.getRole());
        response.getWriter().print("ok");
      } else {
        sendError("El usuario no existe", response);
      }
    } catch (ClassNotFoundException cnfe) {
      cnfe.printStackTrace();
      sendError("Internal Server Error", response);
    } catch (SQLException sqle) {
      sqle.printStackTrace();
      sendError("Error conectando con la base de datos", response);
    }
  }
}