import java.io.*;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.servlet.*;
import javax.servlet.http.*;

public class Login extends HttpServlet {

public void doPost(HttpServletRequest request, HttpServletResponse response)
        throws ServletException, IOException {
    response.setContentType("text/html;charset=UTF-8");
    PrintWriter out = response.getWriter();

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

    /*
    int rechtenopgehaald = 0;
    try {
        rechtenopgehaald = Validate.CheckRechten(email, pass);
    } catch (InstantiationException ex) {
        Logger.getLogger(Login.class.getName()).log(Level.SEVERE, null, ex);
    }
  */
    try {
        if(Validate.checkLogin(email, pass))// && rechtenopgehaald==1)
        {
            RequestDispatcher rs = request.getRequestDispatcher("Welcome");
            rs.forward(request, response);
        }else
        {
            out.println("Username or Password incorrect");
            RequestDispatcher rs = request.getRequestDispatcher("index.html");
            rs.include(request, response);
        }
    } catch (InstantiationException ex) {
        Logger.getLogger(Login.class.getName()).log(Level.SEVERE, null, ex);
    }
}
}

import java.sql.*;

public class Validate {
public static boolean checkLogin(String email,String pass) throws
 {
  boolean validusercheck = false;
  try{
//loading drivers for mysql
     Class.forName("com.mysql.jdbc.Driver");

 //creating connection with the database
     Connection hoi=DriverManager.getConnection("jdbc:mysql://localhost:3306/test","user","pass");
     PreparedStatement ps =hoi.prepareStatement("select rechten from Users where email= ? AND pass= ?");
     ps.setString(1, email);
     ps.setString(2, pass);
     ResultSet rs =ps.executeQuery();
     validusercheck=rs.next();

  }catch(ClassNotFoundException | SQLException e)
  {
      System.out.println(e);
  }
     return validusercheck;

 }

public static int CheckRechten(String email,String pass) throws InstantiationException
 {
  int rechten = 0;

     try{

 //loading drivers for mysql
     Class.forName("com.mysql.jdbc.Driver");

 //creating connection with the database
     Connection hoi=DriverManager.getConnection("jdbc:mysql://localhost:3306/test","user","pass");
     PreparedStatement x =hoi.prepareStatement("select rechten from Users where email= ? AND pass= ?");
     x.setString(1, email);
     x.setString(2, pass);
     ResultSet rs =x.executeQuery();

     while (rs.next()) {
     rechten = rs.getInt(rechten);
     }

  }catch(ClassNotFoundException | SQLException e)
  {
      System.out.println(e);
  }
  return rechten;

 }

}

public void doGet(HttpServletRequest request, HttpServletResponse response)
        throws ServletException, IOException {
    response.setContentType("text/html;charset=UTF-8");
    PrintWriter out = response.getWriter();

    double rente = double.parseouble("rente");
    int jaren = request.getParameter("jaren");
    double lening = request.getParameter("lening");

    double maandrente = berekenmaandrente(rente, lening);
    double aflossing = berekenaflossing(rente, jaren, lening, maandrente);
    out.println("Maandaflossing ="+aflossing);
    out.println("Maandrente ="+maandrente);
}

public double getAnnuity(double a, double b, int c) {
double x = (a/100)/12;
double y = x/(1-Math.pow(((1+x)),-(c*12))) * b;
return y;