Untitled

package mainpackage;

import java.io.*;

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;
/**
 * Servlet implementation class LoginServlet
 */
@WebServlet("/LoginServlet")


public class LoginServlet extends HttpServlet {

	private static final long serialVersionUID = 1L;
	private static String redirect;
	public static  RegisteredUser registeredUser;
	public static Admin admin;
	private static String logged_in;
	private static String this_is_admin;
	public static HomePage homepage = new HomePage();

	/* @see HttpServlet#HttpServlet()
	 */
	public LoginServlet() {
	super();
	 //TODO Auto-generated constructor stub
	}


	/**
	 * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
	 */
	 public void doGet(HttpServletRequest request, HttpServletResponse response)throws IOException{

	 RequestDispatcher rd = request.getRequestDispatcher("jsp/login.jsp");
	 try {
	  rd.forward(request, response);
	 } catch (ServletException e) { e.printStackTrace(); }


	}


	//@see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)

	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// edw pairnoume to onoma tou user apo th forma
		String usernameGiven = request.getParameter("user_name");
		String passwordGiven = request.getParameter("pass_word");


		if (LoginVerification.checkUser(usernameGiven, passwordGiven)){


			String movies[] = homepage.User_Uploads();
			request.setAttribute("movies",movies);
			// an einai o admin mpainei sth selida tou ws admin
			if (usernameGiven.equals("admin")){

				this_is_admin = "true";
				request.setAttribute("this_is_admin",this_is_admin);
				admin = new Admin(usernameGiven,passwordGiven);
				request.setAttribute("username",usernameGiven);
				redirect = "jsp/Homepage.jsp";
			}
			else
			{
				logged_in = "true";
				request.setAttribute("logged_in",logged_in);
				registeredUser = new RegisteredUser(usernameGiven,passwordGiven);
				request.setAttribute("username", usernameGiven);
				redirect = "jsp/Homepage.jsp";

			}

		}
		else
		{
			request.setAttribute("username",usernameGiven);
			redirect = "jsp/logginerr.jsp";
		}

		RequestDispatcher rd = request.getRequestDispatcher(redirect);
		try {
			rd.forward(request, response);
		} catch (ServletException e) { e.printStackTrace(); }
		//ανοιγουμε συνδεση με τη βαση δεδομενων
	}
}

kai to logginerr.jsp

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<% String username = (String)request.getAttribute("username");%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Error</title>
<script language="javascript" type="text/javascript">
        function popitup() {
            alert("Λυπούμαστε αλλά το όνομα χρήστη που πληκτρολογήσατε δεν είναι εγγεγραμμένο στο σύστημα, προσπαθήστε πάλι! ");
            history.back();
        }
	</script>
</head>
<body onload="popitup()">
</body>
</html>