Question

Using the Netbeans GUI builder, is it perhaps a synchronization, thread or pass by value/reference problem which prevents passing a DefaultTableModel from a utility class to a JFrame?

The console output is the same in either case, and the code is just copy/pasted from the utility class and placed in the JFrame. However, if the utility class is used, then there’s no GUI output.

How can I track down why the JTable is blank or empty? So far as I can tell, the DefaultTableModel is populated with data.

console output:

init:
Deleting: /home/thufir/NetBeansProjects/SwingNNTP/build/built-jar.properties
deps-jar:
Updating property file: /home/thufir/NetBeansProjects/SwingNNTP/build/built-jar.properties
Compiling 1 source file to /home/thufir/NetBeansProjects/SwingNNTP/build/classes
warning: [options] bootstrap class path not set in conjunction with -source 1.5
1 warning
compile:
run:
Apr 23, 2012 9:46:25 PM net.bounceme.dur.nntp.EnumNNTP <init>
INFO: SingletonNNTP..only once...
Apr 23, 2012 9:46:25 PM net.bounceme.dur.nntp.PropertiesReader getProps
INFO: NNTP.loadMessages...
Apr 23, 2012 9:46:25 PM net.bounceme.dur.nntp.EnumNNTP connect
INFO: SingletonNNTP.connect..
Apr 23, 2012 9:46:26 PM net.bounceme.dur.nntp.EnumNNTP setIndex
INFO: SingletonNNTP.setIndex..164
Apr 23, 2012 9:46:26 PM net.bounceme.dur.nntp.EnumNNTP page
INFO: SingletonNNTP.page..174
Apr 23, 2012 9:46:26 PM net.bounceme.dur.nntp.EnumNNTP setIndex
INFO: SingletonNNTP.setIndex..164
Apr 23, 2012 9:46:26 PM net.bounceme.dur.nntp.EnumNNTP getMessages
INFO: SingletonNNTP.getMessages..
Apr 23, 2012 9:46:26 PM net.bounceme.dur.nntp.MessageBean setFrom
INFO: MessageBean.setFrom..unknown <[e-mail]>
Apr 23, 2012 9:46:26 PM net.bounceme.dur.nntp.MessageBean setFrom
INFO: MessageBean.setFrom..unknown <[e-mail]>
Apr 23, 2012 9:46:26 PM net.bounceme.dur.nntp.MessageBean setFrom
INFO: MessageBean.setFrom..unknown <[e-mail]>
Apr 23, 2012 9:46:26 PM net.bounceme.dur.nntp.MessageBean setFrom
INFO: MessageBean.setFrom..unknown <[e-mail]>
Apr 23, 2012 9:46:26 PM net.bounceme.dur.nntp.MessageBean setFrom
INFO: MessageBean.setFrom..unknown <[e-mail]>
Apr 23, 2012 9:46:26 PM net.bounceme.dur.nntp.MessageBean setFrom
INFO: MessageBean.setFrom..unknown <[e-mail]>
Apr 23, 2012 9:46:26 PM net.bounceme.dur.nntp.MessageBean setFrom
INFO: MessageBean.setFrom..unknown <[e-mail]>
Apr 23, 2012 9:46:26 PM net.bounceme.dur.nntp.MessageBean setFrom
INFO: MessageBean.setFrom..unknown <[e-mail]>
Apr 23, 2012 9:46:26 PM net.bounceme.dur.nntp.MessageBean setFrom
INFO: MessageBean.setFrom..unknown <[e-mail]>
Apr 23, 2012 9:46:26 PM net.bounceme.dur.nntp.MessageBean setFrom
INFO: MessageBean.setFrom..unknown <[e-mail]>
Apr 23, 2012 9:46:26 PM net.bounceme.dur.nntp.MessageBean setFrom
INFO: MessageBean.setFrom..unknown <[e-mail]>
Apr 23, 2012 9:46:27 PM net.bounceme.dur.nntp.MessageUtils getDataTableModel
INFO: unknown <[e-mail]>Sun Apr 22 02:58:24 PDT 2012The return of the euro crisis: Beyond battlefield medicine
Apr 23, 2012 9:46:27 PM net.bounceme.dur.nntp.MessageUtils getDataTableModel
INFO: unknown <[e-mail]>Sun Apr 22 02:58:24 PDT 2012North Korea’s gulag: Never again?
Apr 23, 2012 9:46:27 PM net.bounceme.dur.nntp.MessageUtils getDataTableModel
INFO: unknown <[e-mail]>Sun Apr 22 02:58:24 PDT 2012Nationalising YPF: Cristina scrapes the barrel
Apr 23, 2012 9:46:27 PM net.bounceme.dur.nntp.MessageUtils getDataTableModel
INFO: unknown <[e-mail]>Sun Apr 22 02:58:23 PDT 2012Charlemagne: April showers on the euro
Apr 23, 2012 9:46:27 PM net.bounceme.dur.nntp.MessageUtils getDataTableModel
INFO: unknown <[e-mail]>Sun Apr 22 02:58:23 PDT 2012Jihadist terrorism: Al-Qaeda is down, but far from out
Apr 23, 2012 9:46:27 PM net.bounceme.dur.nntp.MessageUtils getDataTableModel
INFO: unknown <[e-mail]>Sun Apr 22 02:58:23 PDT 2012Justice for dictators: History rules
Apr 23, 2012 9:46:27 PM net.bounceme.dur.nntp.MessageUtils getDataTableModel
INFO: unknown <[e-mail]>Sun Apr 22 02:58:23 PDT 2012Buttonwood: Feeling peaky
Apr 23, 2012 9:46:27 PM net.bounceme.dur.nntp.MessageUtils getDataTableModel
INFO: unknown <[e-mail]>Sun Apr 22 02:58:23 PDT 2012Couples and housework: The ironing lady
Apr 23, 2012 9:46:27 PM net.bounceme.dur.nntp.MessageUtils getDataTableModel
INFO: unknown <[e-mail]>Sun Apr 22 02:58:23 PDT 2012Markets
Apr 23, 2012 9:46:27 PM net.bounceme.dur.nntp.MessageUtils getDataTableModel
INFO: unknown <[e-mail]>Sun Apr 22 02:58:22 PDT 2012The World Bank: Kim selection
Apr 23, 2012 9:46:27 PM net.bounceme.dur.nntp.MessageUtils getDataTableModel
INFO: unknown <[e-mail]>Sun Apr 22 02:58:22 PDT 2012The Economist commodity-price index
BUILD SUCCESSFUL (total time: 13 seconds)

the commented out code in the MessagesJFrame actually works, while passing that off to the utility class introduces problems — an apparently empty JTable.

JFrame:

package net.bounceme.dur.nntp;

import java.util.List;
import java.util.Vector;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.mail.Message;
import javax.swing.table.DefaultTableModel;

public class MessagesJFrame extends javax.swing.JFrame {

    private DefaultTableModel defaultTableModel = new DefaultTableModel();

    public MessagesJFrame() throws Exception {
        initComponents();
        MessageUtils.loadMessages();
        defaultTableModel = MessageUtils.getDataTableModel();
        /*
        EnumNNTP nntp = EnumNNTP.INSTANCE;
        List<Message> listOfMessages = nntp.getMessages(false);//nntp debug off
        Vector messages = new Vector();
        for (Message m : listOfMessages) {
            MessageBean messageBean = new MessageBean(m);
            messages.add(messageBean);
        }
        defaultTableModel.addColumn("from");
        defaultTableModel.addColumn("sent");
        defaultTableModel.addColumn("subject");
        for (Object o : messages) {  //awkward Vector manipulation
            MessageBean messageBean = (MessageBean) o;
            Vector messageBeanAsVector = messageBean.getVector();
            defaultTableModel.addRow(messageBeanAsVector);
        }*/
    }

    /**
     * This method is called from within the constructor to initialize the form.
     * WARNING: Do NOT modify this code. The content of this method is always
     * regenerated by the Form Editor.
     */
    @SuppressWarnings("unchecked")
    // <editor-fold defaultstate="collapsed" desc="Generated Code">
    private void initComponents() {

        jScrollPane1 = new javax.swing.JScrollPane();
        jTable1 = new javax.swing.JTable();

        setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);

        jTable1.setModel(defaultTableModel);
        jScrollPane1.setViewportView(jTable1);

        javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
        getContentPane().setLayout(layout);
        layout.setHorizontalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(javax.swing.GroupLayout.Alignment.TRAILING, layout.createSequentialGroup()
                .addContainerGap()
                .addComponent(jScrollPane1, javax.swing.GroupLayout.DEFAULT_SIZE, 819, Short.MAX_VALUE)
                .addContainerGap())
        );
        layout.setVerticalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(layout.createSequentialGroup()
                .addContainerGap()
                .addComponent(jScrollPane1, javax.swing.GroupLayout.DEFAULT_SIZE, 455, Short.MAX_VALUE)
                .addContainerGap())
        );

        pack();
    }// </editor-fold>

    /**
     * @param args the command line arguments
     */
    public static void main(String args[]) {
        /*
         * Set the Nimbus look and feel
         */
        //<editor-fold defaultstate="collapsed" desc=" Look and feel setting code (optional) ">
        /*
         * If Nimbus (introduced in Java SE 6) is not available, stay with the
         * default look and feel. For details see
         * http://download.oracle.com/javase/tutorial/uiswing/lookandfeel/plaf.html
         */
        try {
            for (javax.swing.UIManager.LookAndFeelInfo info : javax.swing.UIManager.getInstalledLookAndFeels()) {
                if ("Nimbus".equals(info.getName())) {
                    javax.swing.UIManager.setLookAndFeel(info.getClassName());
                    break;
                }
            }
        } catch (ClassNotFoundException ex) {
            java.util.logging.Logger.getLogger(MessagesJFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (InstantiationException ex) {
            java.util.logging.Logger.getLogger(MessagesJFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (IllegalAccessException ex) {
            java.util.logging.Logger.getLogger(MessagesJFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (javax.swing.UnsupportedLookAndFeelException ex) {
            java.util.logging.Logger.getLogger(MessagesJFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        }
        //</editor-fold>

        /*
         * Create and display the form
         */
        java.awt.EventQueue.invokeLater(new Runnable() {

            public void run() {
                try {
                    new MessagesJFrame().setVisible(true);
                } catch (Exception ex) {
                    Logger.getLogger(MessagesJFrame.class.getName()).log(Level.SEVERE, null, ex);
                }
            }
        });
    }
    // Variables declaration - do not modify
    private javax.swing.JScrollPane jScrollPane1;
    private javax.swing.JTable jTable1;
    // End of variables declaration
}

utility class:

package net.bounceme.dur.nntp;

import java.util.Iterator;
import java.util.List;
import java.util.Vector;
import java.util.logging.Logger;
import javax.mail.Message;
import javax.swing.table.DefaultTableModel;

public class MessageUtils {

    private static final long serialVersionUID = 1L;
    private static final Logger LOG = Logger.getLogger(MessageUtils.class.getName());
    private static DefaultTableModel defaultTableModel = new DefaultTableModel();
    private static EnumNNTP nntp = EnumNNTP.INSTANCE;
    private static Vector messages = new Vector();

    public static void loadMessages() throws Exception {
        List<Message> listOfMessages = nntp.getMessages(false);//nntp debug off
        messages.clear();
        for (Message m : listOfMessages) {
            MessageBean messageBean = new MessageBean(m);
            messages.add(messageBean);
        }
        loadTableModel();
    }

    private static void loadTableModel() {
        defaultTableModel = new DefaultTableModel();
        defaultTableModel.addColumn("from");
        defaultTableModel.addColumn("sent");
        defaultTableModel.addColumn("subject");
        for (Object o : messages) {  //awkward Vector manipulation
            MessageBean messageBean = (MessageBean) o;
            Vector messageBeanAsVector = messageBean.getVector();
            defaultTableModel.addRow(messageBeanAsVector);
        }
    }

    public static DefaultTableModel getDataTableModel() {
        Vector vector = defaultTableModel.getDataVector();
        Iterator it = vector.iterator();
        while (it.hasNext()) {
            Vector v = (Vector) it.next();
            Iterator i = v.iterator();
            StringBuilder row = new StringBuilder();
            while (i.hasNext()) {
                row.append(i.next());
            }
            LOG.info(row.toString());
        }
        return defaultTableModel;
    }

    public static void setDataTableModel(DefaultTableModel dataTableModel) {
        MessageUtils.defaultTableModel = dataTableModel;
    }

    public static Vector getMessages() {
        return messages;
    }

    public static void setMessages(Vector messages) {
        MessageUtils.messages = messages;
    }
}

Answer 1

Of course you end up with an empty JTable. You have two instances called defaultTableModel which have nothing in common. You will need to pass the defaultTableModel you use in your UI to the utility class, and let the utility class populate that particular model (or the other way around, set the defaultTableModel instance used in your utility class as the model of the JTable).

Edit

Just to be clear, the problem is that you probably think that

defaultTableModel = MessageUtils.getDataTableModel();

will adjust the model you have set on your JTable, but it doesn’t. It just makes your defaultTableModel field refer another TableModel then the original one. If you would just move this line to be the first of your constructor, your code will work since you will actually set the result of MessageUtils.getDataTableModel() as the TableModel of your JTable