How can I solve problem "Cannot parse null string"? in Java(SignUp.JSP)

Here's my error

java.lang.NumberFormatException: Cannot parse null string

but I didn't do anything Shape conversion.

I would make SignUp Page but some problems persistently can't solve it.

I made SignUpcontroller which name MemberController, JSP file, MemberDAO class and MemberVO classs

Why is there an error...?

And I cant connect My DataBase

I did it for seven hours. Please help me........[enter image description here][1]

That code is MemberController code what I write

Member/MemberController.java

package Member;

import java.io.IOException;

import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;


public class MemberController extends HttpServlet {
    private static final long serialVersionUID = 1L;

    /**
     * @see HttpServlet#HttpServlet()
     */

    /**
     * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse
     *      response)
     */
    protected void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        // TODO Auto-generated method stub
//      response.getWriter().append("Served at: ").append(request.getContextPath());

    }

    /**
     * @param application
     * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse
     *      response)
     */
    protected void doPost(HttpServletRequest req, HttpServletResponse resp, ServletContext application)
            throws ServletException, IOException {
        // TODO Auto-generated method stub
        doGet(req, resp);
        req.getRequestDispatcher("/Page/SignUp2.jsp").forward(req, resp);

        // 폼값을 DTO에 저장
        MemberDTO dto = new MemberDTO();

        dto.setName(req.getParameter("name"));
        dto.setNickname(req.getParameter("nickname"));
        dto.setUser_id(req.getParameter("user_id"));
        dto.setUser_passwd(req.getParameter("user_passwd"));
        dto.setEmail(req.getParameter("email"));
        dto.setPhone_num(req.getParameter("phone_num"));
        dto.setUser_picture(req.getParameter("user_picture"));

        // DAO를 통해 DB에 게시 내용 저장
        MemberDAO dao = new MemberDAO();

        int result = dao.signUp(dto);
        dao.close();

        // 성공 or 실패?
        if (result == 1) {
            resp.sendRedirect("./Page/SignUp3.jsp");
        } else {
            resp.sendRedirect("./Page/SignUp2.jsp");
        }
    }

}

Member/MemberDAO.java

package Member;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.Statement;

import javax.naming.Context;
import javax.naming.InitialContext;
import javax.servlet.ServletContext;
import javax.sql.DataSource;

import common.DBConnPool;
import common.JDBConnect;

public class MemberDAO extends JDBConnect {

    public MemberDAO() {

    }

    public MemberDAO(String drv, String url, String id, String pw) {
        super(drv, url, id, pw);
    }

    // 회원가입
    public int signUp(MemberDTO dto) {
        int result = 0;

        String query = "INSERT INTO memberTB ( "
                + " idx, name, nickname, user_id, user_passwd, email, phone_num, user_picture) " + " VALUES ( "
                + " seq_board_num.NEXTVAL,?,?,?,?,?,?,?)";

        try {
            psmt = con.prepareStatement(query);
            psmt.setString(1, dto.getName());
            psmt.setString(2, dto.getNickname());
            psmt.setString(3, dto.getUser_id());
            psmt.setString(4, dto.getUser_passwd());
            psmt.setString(5, dto.getEmail());
            psmt.setString(6, dto.getPhone_num());
            psmt.setString(7, dto.getUser_picture());
            result = psmt.executeUpdate();

        } catch (Exception e) {
            System.out.println("회원가입 중 예외 발생");
            e.printStackTrace();
        }
        return result;
    }
}