LoginController.java

package controller;

import java.io.IOException;
import java.sql.SQLException;

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

import bean.MailList;
import dao.MailListDAO;

/**
 * Servlet implementation class LoginController
 */
@WebServlet("/LoginController")
public class LoginController extends HttpServlet {
	private static final long serialVersionUID = 1L;
       
    public LoginController() {
        super();
    }

	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// 0. 先檢查他是不是有 session 的資料
		HttpSession session  = request.getSession();
		String email = (String)session.getAttribute("email");
		String phone = (String)session.getAttribute("phone");
		
		// 如果有，就執行 doPOST();
		if(email != null && phone != null) {
			doPost(request, response);
		} else {
		    // 如果沒有，就導向登入頁面。
			RequestDispatcher requestDispatcher = request.getRequestDispatcher("login.jsp");
			response.setCharacterEncoding("UTF-8");
			response.setContentType("text/html;charset=UTF-8");
			requestDispatcher.forward(request, response);
		}
	}

	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		
		HttpSession session  = request.getSession();
		String sessionEmail = (String)session.getAttribute("email");
		String sessionPhone = (String)session.getAttribute("phone");
		
		String email;
		String phone;
		if(sessionEmail == null && sessionPhone == null) { // Session 沒有值
			// 取得 Email 和 Phone 
			email = request.getParameter("email"); 
			phone = request.getParameter("phone"); 
			System.out.println("Requset " + email + " :" + phone);
			
			// 1. 把使用者提供資訊放到 session 裡面。
			session.setAttribute("email", email); 
			session.setAttribute("phone", phone); 
		} else {
			email = sessionEmail;
			phone = sessionPhone;
		}
		
		// 到資料庫去找，這個 email 以及 這個電話是不是已經填過？
		try {
			MailList mailList = MailListDAO.findByEmailAndPhone(email, phone);
			
			if(mailList != null) {
				request.setAttribute("mailList", mailList);
			    RequestDispatcher requestDispatcher = request.getRequestDispatcher("/sign-up-complete.jsp");
			    requestDispatcher.forward(request, response);
			} else {
			    RequestDispatcher requestDispatcher = request.getRequestDispatcher("/sign-up.jsp");
			    requestDispatcher.forward(request, response);
			}
			
		} catch (ClassNotFoundException | SQLException e) {
			e.printStackTrace();
		}
		
	}

}