如何让我的程序在 JtextField 中显示数据库中的用户名？

Question

I'm making a program where you login and it takes you into a into a different frame after you log in.. That part of the program works, but I'm having trouble getting it to return the user's name and other data from the database. It connects to the database, but it won't return the information inside JTextField. If I can find out how to do firstName, I can figure out the rest. I'm using Eclipse as my IDE and SQLite Manager as the database. There are 2 tables Login (username,password) Student(SID,firstName,GradeLevel, and more) Also username is there ID start with an S (like S01 and so forth). Here's the code.

public class student extends JFrame {
private JTextField textField;

public static void main(String[] args) {
    EventQueue.invokeLater(new Runnable() {
        public void run() {
            try {
                student frame = new student();
                frame.setVisible(true);
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    });
}
private void ShowInfo() {

try{


    String query="SELECT firstName From Student,Login Where firstname=?";
    PreparedStatement ps=conn.prepareStatement(query);
    ps.setString(1, "firstName");
    ResultSet rs= ps.executeQuery();
    while (rs.next()) {
    textField.setText(rs.getString("firstName"));
        System.out.print(""+textField);
    }ps.close();
    conn.close();
    } catch ( Exception ex)
    {

        JOptionPane.showMessageDialog(null,ex);
}


}

}

Answer 1

private void ShowInfo() {

try{
    String query="SELECT firstName From Student,Login Where firstname=?";
    PreparedStatement ps=conn.prepareStatement(query);
    ps.setString(1, "firstName");
    ResultSet rs= ps.executeQuery();
    if(rs.next()) {
    textField.setText(rs.getString(1));
    System.out.print(""+textField); //you are getting data
    }ps.close();
    conn.close();
    } catch ( Exception ex)
    {
        JOptionPane.showMessageDialog(null,ex); //you have a error
}
}

there were sevral thing which were wrong in the code. first one is there should be something wrong with sql statment Student,Login Where firstname . you should change this line textField.setText(rs.getString(1)); and you have a while loop to extract the data but and you are planning on having a textfield to store data. that is pointless if you are expecting more than one output from your resultset you need something more than a jtextfield maybe a jtable. bt i have changed your while loop to a if loop to get one single output from the resultset.and the other thing i notice in your application is you are not calling the showInfo method.