Binding a Actionlistener (button) to Resultset.next

Question

I need to make a program that asks data from a mysql database displays it. (in the full program it also needs to be able to create, alter and delete rows but I'm already stuck with displaying). The way I went at this is by making a connection with jdbc. Then execute a query and put that in a resultset. Then using a if statement to get the first row of information with resultset.next and a bunch of parsestring and settext methods.

The next step is a next and previous button to scroll through the resultset and display the information.

My plan was to put a rs.next() in the actionlistener and redo all the setTexts on the textfields with the new strings but I've tried to a 100 different ways it feels like but I keep getting errors one way or the other.

Someone also suggested I should try and set the actionlistener to add 1 to a variable. And then putting the rest of the code in a class where I can call it with a method but I don't know how to make a method like that.

Any help whatsoever would be amazing. I've been coding for only a few weeks now and I'm feeling like I am in way over my head. So if there are any other things I'm doing wrong please tell me. Cheers

The code

package duo.opdracht.info.pagina;

import javax.swing.*;
import java.awt.event.*;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.sql.*;

public class DUOOpdrachtInfoPagina extends JFrame {

  public static void main(String[] args) {
    JFrame frame = new DUOOpdrachtInfoPagina();
    frame.setSize(1000, 750);
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.setTitle("Optredens");
    frame.setContentPane(new Paneel());
    frame.setVisible(true);

  }
}

class Paneel extends JPanel {

  private JButton volgendeKnop, vorigeKnop;
  private JTextField bandArtiestVak, starttijdVak, eindtijdVak, podiumVak;
  private JLabel bandArtiestLabel, starttijdLabel, eindtijdLabel, podiumLabel;

  public Paneel() {
    setLayout(null);

    volgendeKnop = new JButton("Volgende");
    volgendeKnop.addActionListener(new ButtonHandler());
    vorigeKnop = new JButton("Vorige");

    bandArtiestVak = new JTextField(20);
    starttijdVak = new JTextField(20);
    eindtijdVak = new JTextField(20);
    podiumVak = new JTextField(20);

    bandArtiestLabel = new JLabel("Artiest / Band: ");
    starttijdLabel = new JLabel("Starttijd: ");
    eindtijdLabel = new JLabel("Eindtijd: ");
    podiumLabel = new JLabel("Podium: ");

    volgendeKnop.setBounds(850, 600, 100, 25);
    vorigeKnop.setBounds(50, 600, 100, 25);
    bandArtiestVak.setBounds(200, 100, 300, 25);
    starttijdVak.setBounds(200, 130, 300, 25);
    eindtijdVak.setBounds(200, 160, 300, 25);
    podiumVak.setBounds(200, 190, 300, 25);
    bandArtiestLabel.setBounds(100, 100, 300, 25);
    starttijdLabel.setBounds(100, 130, 300, 25);
    eindtijdLabel.setBounds(100, 160, 300, 25);
    podiumLabel.setBounds(100, 190, 300, 25);

    bandArtiestVak.setEditable(false);
    starttijdVak.setEditable(false);
    eindtijdVak.setEditable(false);
    podiumVak.setEditable(false);

    add(volgendeKnop);
    add(vorigeKnop);
    add(bandArtiestVak);
    add(starttijdVak);
    add(eindtijdVak);
    add(podiumVak);
    add(bandArtiestLabel);
    add(starttijdLabel);
    add(eindtijdLabel);
    add(podiumLabel);

    // create our mysql database connection
    try {
      Connection conn = DriverManager.getConnection("jdbc:mysql://localhost/DUO_1", "duo1", "duo1");

      Statement stmt = null;
      String query
              = "SELECT BandArtiestNaam, Starttijd, Eindtijd, Podiumnaam FROM optreden";

      stmt = conn.createStatement(
              ResultSet.TYPE_SCROLL_INSENSITIVE,
              ResultSet.CONCUR_READ_ONLY);

      ResultSet rs = stmt.executeQuery(query);
      if (rs.next()) {
        String naam = rs.getString(1);
        String stijd = rs.getString(2);
        String etijd = rs.getString(3);
        String pnaam = rs.getString(4);

        bandArtiestVak.setText(naam);
        starttijdVak.setText(stijd);
        eindtijdVak.setText(etijd);
        podiumVak.setText(pnaam);

      }
    } catch (SQLException e) {
      System.out.println(e);
    }
  }

  class ButtonHandler implements ActionListener {

    public void actionPerformed(ActionEvent e) {

    }
  }
}

Answer 1

Break your problem down into different concerns, you shouldn't have a class which does absolutely everything in your application. You will find, as you are right now, that when you have a problem, it is very hard to track down, much harder than you could have ever imagined. Lets rather start by breaking this problem down into manageable chunks, that's really all programming is.

• View - your actual Swing panel with the other panels, this should have nothing other than just a bunch of panels and buttons, do not have any sql code there, and don't have any, (or extremely view) listeners, absolutely nothing but the view.
• Dao (data access object) - This class has all your SQL code, the only thing it does is perform CRUD operations. It may do some other stuff to change a result set into something more meaningful, it may be a good idea to contain the result set to this class, as this is a concern of the dao. In general people use things like hibernate instead of writing SQL code but your free to do as you please, but I encourage you to check it out.
• Controller - This will be the link between your View, and your Dao. It will take both of these as parameters in its constructor. The controller will add action listeners to wherever it needs to in your view, take any inputs from the view, and call the Dao with the corresponding input arguments, and return this back to the view as needed.

This is a design pattern called MVC - (model view controller) different variations exist for different applications desktop/web ect. This will allow you to separate each concern into the relevant component, and test to see if each one is working, and where the problem is. You will be able to test, for instance the Dao, without needing to create a view and add listeners. Sounds like you are learning so I strongly suggest you learn this design pattern. You will find that you are unable to make a substantial application with your current design, as problems becoming ever increasingly harder to track down, and new functionality harder to add.

A few more things, you should really just convert the whole result set into something more meaningful, it's already loaded. Using rs.next every time you want a new row will mean you cannot close the result set, and you'll probably have all these resource warnings. Otherwise check out hibernate. I very much liked this site when I was starting to learn programming in Java, I suggest you check it out https://www.caveofprogramming.com/java-design-patterns/mvc-example.html