Untitled

<html>
  <head>
    <!-- more scripts / google api js are here -->
    <script type="text/javascript">
      function get_action(form) {
        var v = grecaptcha.getResponse();
        if(v.length === 0) {
           document.getElementById('captcha').innerHTML="Login failed: Empty captcha";
           return false;
        } else {
           return true;
        }
      }
    </script>
  </head>
  <body>
    <form action="login" method="post" onsubmit="return get_action(this);">
       <input type="text" id="email" value="${fn:escapeXml(param.email)}" required>
       <input type="text" id="password" value="${fn:escapeXml(param.password)}" required>
       <div class="g-recaptcha" data-sitekey="xxx"></div>
       <input class="submit_button" type="submit" name="submit" value="Submit" />
       <span class="error"${error.invalid}</span>
       <div id="captcha" class="captchaError"></div>
    </form>
  </body>
</html>

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

    private LoginDAO loginDAO;

    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response)
        throws ServletException, IOException {
        request.getRequestDispatcher("login.jsp").forward(request,response);
    }

    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response)
        throws ServletException, IOException {
        Map<String, String> error = new HashMap<String,String>();
        request.setAttribute("error",error);

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

        // Verify re-captcha
        String gRecaptchaResponse = request.getParameter("captcha");
        boolean verify = VerifyRecaptcha.verify(gRecaptchaResponse);
        if(!verify) {
            error.put("captcha","You seem to be a robot. Try to use the captcha again");
        }
        if(error.isEmpty()) {
            loginDAO = new LoginDAO();
            try {
                List<Customer> customer = new ArrayList<Customer>();
                customer = loginDAO.validate(email,password);
                if(customer.isEmpty()) {
                    error.put("invalid","Invalid email or password");
                }
                if(error.isEmpty()) { // no errors, proceed
                    HttpSession session = request.getSession(true);
                    Customer user = customer.get(0);
                    session.setAttribute("user",user);
                    response.sendRedirect("main");
                    return;
                }
                request.getRequestDispatcher("login").forward(request,response);
            } catch(SQLException e) {
                throw new ServletException("Could not check login",e);
            }
            loginDAO.closeLoginDAO();
        }
    }
}