使用计数登录桌面应用程序

Question

I am trying to call a page when a user validates as "Admin" or "User" but there seems to be a problem.

private void validateLogin() {
    if (getFieldData() == true) {
        username = txtname.getText();
        String password = new String(txtpassword.getPassword());
        Object type = cbType.getSelectedItem();
        //validate login and password here. 
        //validity will be done by sending login/password to the database
        String sql = "select  count(*) from usermanagement where UserName='" 
                + username + "' and " + "Password='" + password + "'";
        ResultSet rs = datacon.queryTable(sql);
        try {
            rs.next();
            if (rs.getInt(1) > 0) {
                if (type.equals("Admin")) {
                    MainMenu mainmenu = new MainMenu();
                    this.dispose();
                    mainmenu.setVisible(true);
                } else {
                    UserMenu usermenu = new UserMenu();
                    this.dispose();
                    usermenu.setVisible(true);
                }
            } else {
                JOptionPane.showMessageDialog(this, 
                        "Incorrect username or password or user category", 
                        "Error", JOptionPane.ERROR_MESSAGE);
                clearField();
                txtname.requestFocusInWindow();
                cbType.setSelectedIndex(0);
            }
        } catch (SQLException ex) {
            ex.printStackTrace();
        }
    }
}

Answer 1

I am not seeing the your inputs here, username and password. It would be best to attach your logs to get a glimpse of what the Exception states about your problem.

From what I see in code here are my suggestions,

• You should refrain from using this UserName='"+username +"' on your sqls, this is appalling for special Charaters can break your sql. I suggest you adhere to something like PreparedStatement http://docs.oracle.com/javase/tutorial/jdbc/basics/prepared.html

• It's better to adhere if(rs.next()) to check if record exists. it's not safe to access rs.getInt(1) , If you're not having any matching records, it can break your application.