如何从数据库中检索值并将它们加载到 JTable 中？

Question

我正在尝试从数据库加载值并将它们列出到 jtable 中。 我的语句正确执行，但是当我加载应用程序时，表空间中没有任何内容，也没有收到任何错误消息。 是否缺少声明？ 我以前没有使用过 jtable。 我已经编辑了原始帖子以包含我的所有代码以引入上下文

//imports

public class viewMusic extends JFrame {

static Connection conn = null;
static viewMusic frame = new viewMusic();  
private JPanel contentPane;
private JTable table;
private JTable table_1;

/**
 * Launch the application.
 */
public static void main(String[] args) {
    EventQueue.invokeLater(new Runnable() {
        public void run() {
            try {
                viewMusic frame = new viewMusic();
                //frame.setVisible(true);
                try { //Login details for the DB.
                    String userName = "root";
                    String password = "";
                    String url = "jdbc:mysql://localhost/music";
                    conn = DriverManager.getConnection(url, userName, password);
                    //JOptionPane.showMessageDialog(null, "Connected");                     
                } catch (Exception e) { //Error is DB connection is unsuccessful .
                    JOptionPane.showMessageDialog(null, "Cannot connect to database server");
                    // System.err.println(e.getMessage());
                    System.err.println(e.getStackTrace());
                }
            } catch (Exception e) {
                e.printStackTrace();
            }               
            Statement stmt;
            try {
                stmt = conn.createStatement();                  
                DefaultTableModel model = new DefaultTableModel(new String[]{"Artist_Name", "Album_Title", "Record_Label", "Genre", "Year", "Format"}, 0);                      
                JTable table = new JTable(model);                   
                String query="SELECT * from cds";   
                System.out.println(query);
                ResultSet rs = stmt.executeQuery(query);

                   String a = "artist";
                   String b = "album title";
                   String c = "record label";
                   String d = "genre";                       
                   String e = "year";                        
                   String f = "format";

                model.addRow(new Object[]{a, b, c, d, e, f});
                table.setModel(model);
                   JScrollPane scrollpane = new JScrollPane(table);
                   frame.getContentPane().add(scrollpane);
                   frame.setSize(600, 500);
                   frame.setVisible(true);

            } catch (Exception e) { //Error is DB connection is unsuccessful .
                JOptionPane.showMessageDialog(null, "Cannot connect");
                // System.err.println(e.getMessage());
                System.err.println(e.getStackTrace());
            }   
        } //End of run()
    });
} //End of main

/**
 * Create the frame.
 */
public viewMusic() {

    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    setBounds(100, 100, 600, 400);
    contentPane = new JPanel();
    contentPane.setBorder(new EmptyBorder(5, 5, 5, 5));
    setContentPane(contentPane);
    contentPane.setLayout(null);

    table_1 = new JTable();
    table_1.setBounds(25, 64, 551, 250);
    contentPane.add(table_1);

    JLabel lblStatus = new JLabel("Connection Status");
    lblStatus.setBounds(399, 18, 149, 13);
    contentPane.add(lblStatus);
    lblStatus.setText("Connecting to DB..");
}
}

Answer 1

您需要将 JTable 添加到 JFrame

import java.awt.EventQueue;

import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTable;
import javax.swing.border.EmptyBorder;
import javax.swing.table.DefaultTableModel;

public class ViewMusic extends JFrame {
   private static final long serialVersionUID = 1L;

   // static Connection conn = null;
   static ViewMusic frame = new ViewMusic();
   private JPanel contentPane;
   private static JTable table;
   private static DefaultTableModel model;
   // private JTable table_1;

   /**
    * Launch the application.
    */
   public static void main(String[] args) {
      EventQueue.invokeLater(new Runnable() {
         public void run() {

            model = new DefaultTableModel(new Object[] { "Artist_Name",
                  "Album_Title", "Record_Label", "Genre", "Year", "Format" },
                  0);

            String a = "artist";
            String b = "album title";
            String c = "record label";
            String d = "genre";
            String e = "year";
            String f = "format";

            model.addRow(new Object[] { a, b, c, d, e, f });
            table.setModel(model);

            frame.repaint();

         }
      });
   } // End of main

   /**
    * Create the frame.
    */
   public ViewMusic() {

      setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      setBounds(100, 100, 600, 400);
      contentPane = new JPanel();
      contentPane.setBorder(new EmptyBorder(5, 5, 5, 5));
      setContentPane(contentPane);
      contentPane.setLayout(null);

      table = new JTable();
      JScrollPane scrollpane = new JScrollPane(table);
      scrollpane.setBounds(25, 64, 551, 250);
      contentPane.add(scrollpane);

      JLabel lblStatus = new JLabel("Connection Status");
      lblStatus.setBounds(399, 18, 149, 13);
      contentPane.add(lblStatus);
      lblStatus.setText("Connecting to DB..");

      setVisible(true);
   }
}