Java EE (Java Enterprise Edition) General Discussion

Hi All, My problem is simple I think, So I will post all my classes. I coldn`t connect the database with these code. Where is the my problem. It says to me " user not found."

This is my User class

public class User {

    public String validate(String username, String password) {

    	PreparedStatement stmt = null;
        ResultSet result = null;
        String stmtSQL;
        String id = null;
            try {
            	Connection conn = ConnectionManager.getInstance().getConnnection();         // maybe problem here????
                stmtSQL = "SELECT id FROM login WHERE username = ? AND password = ?";
                stmt = conn.prepareStatement(stmtSQL);
                
                stmt.setString(1, username);
                stmt.setString(2, password);
                
                result = stmt.executeQuery();
                if (result.next()) {
                    id = result.getString("id");
                }
                stmt.close();
                conn.close();
                conn = null;
            } catch (Exception e) {
                e.printStackTrace();
            } 
        return id;
    }
}

this is controller

public class LoginController extends HttpServlet {

    //**doPost����\�
    public void doPost(HttpServletRequest request, HttpServletResponse response)
            throws IOException, ServletException {
    	//buralarda bir yerde connection open yapmam lazim.
    	 try {
    		ConnectionManager.open(); // I think my problem at this point but how will I solve it?
		} catch (SQLException e) {
			e.printStackTrace();
		} // public ConnectionManager(){ hoshii   keredemo dou suru ka??			
		    	
        response.setContentType("text/html;charset=UTF-8"); 
        String username = request.getParameter("username");
        String password = request.getParameter("password");

        try {
            //look at the User class and inside the database
            String loginId;
            if ((loginId = new User().validate(username, password)) != null) {

                request.setAttribute("id", loginId);
                request.setAttribute("username", username);

                getServletContext().getRequestDispatcher("/MainController").forward(request, response);
            } else {
                response.sendRedirect("/swallow/");
            }
        } catch (Throwable t) {
            System.out.println("User not found");
        }
    }

    public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        doPost(request, response);
    } //doGet
}

and this is connection manager class

public final class ConnectionManager {
	private static ConnectionManager instance = new ConnectionManager();
	private Properties prop;
	//private ThreadLocal<Connection> connections = new ThreadLocal<Connection>();
	private static ThreadLocal<Connection> connections = new ThreadLocal<Connection>();

	private ConnectionManager(){
		//public ConnectionManager(){
		ClassLoader cl = instance.getClass().getClassLoader();
		InputStream is = cl.getResourceAsStream("swallowJDBC.properties");
		prop = new Properties();
		try {
			prop.load(is);
		} catch (IOException e) {
			e.printStackTrace();
		}
	}
	
		public static ConnectionManager getInstance() throws IOException {		
		return instance;
	}
		//public void open() throws SQLException {
		 public static void open() throws SQLException {  // I think most probably my problem happen  here but where is it ????
		Connection conn = null; // open connection for this thread.
		 try {
		 String driver = ((Properties) conn).getProperty("swallow.jdbc.driver");
		 String url = ((Properties) conn).getProperty("swallow.jdbc.url");
		 String user = ((Properties) conn).getProperty("swallow.jdbc.user");
		 String password = ((Properties) conn).getProperty("swallow.jdbc.password");
		 Class.forName(driver);
		 //return DriverManager.getConnection(url, user, password);
		 conn = DriverManager.getConnection(url, user, password);
		} catch (ClassNotFoundException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		connections.set(conn);
	}

	public Connection getConnnection() {
		
		return connections.get();
	}

	public void commit() throws SQLException {
		Connection conn = getConnnection();
		if (conn != null) {
			conn.commit();
			conn.close();
		}
	}
	 public void rollback() throws SQLException {
		 Connection conn = getConnnection();
	        if (conn != null) {
	            conn.rollback();
	            conn.close();
	        }
	    }
	
}

i am sorry I sent all codes... but I know you can undestand on my mistakes easly... please help...