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Monday, 6 March 2017

Chapter 32 Exercise 6, Introduction to Java Programming, Tenth Edition Y. Daniel LiangY.

32.6 (Find tables and showing their contents) Write a program that fills in table names in a combo box, as shown in Figure 32.30b. You can select a table from the combo box to display its contents in the text area.


import javax.swing.*;
import javax.swing.border.EmptyBorder;

import java.sql.*;
import java.util.Vector;
import java.awt.*;
import java.awt.event.*;

public class Exercise06 extends JApplet {
 private static final long serialVersionUID = 1L;
 private JComboBox<String> jComboBox;
 private Vector<String> tableNames = new Vector<>();
 private JTextArea jTextArea = new JTextArea();
 
 private Statement statement;

 /** Initialize the applet */
 public void init() {
  initializeDB();
  jComboBox = new JComboBox<String>(tableNames);
  jComboBox.addActionListener(new ActionListener() {
   @Override
   public void actionPerformed(ActionEvent e) {
    jbtShowTable_actionPerformed(e);
   }
  });
  
  jTextArea.setEditable(false);
  jTextArea.setFont(new Font(Font.MONOSPACED, Font.BOLD, 12));
  JScrollPane jScrollPane = new JScrollPane(jTextArea);
  setLayout(new BorderLayout(5, 5));
  JPanel jPanel1 = new JPanel(new BorderLayout(5, 5));
  jPanel1.setBorder(new EmptyBorder(5, 5, 5, 5));
  jPanel1.add(jComboBox, BorderLayout.NORTH);
  jPanel1.add(jScrollPane, BorderLayout.CENTER);
  add(jPanel1, BorderLayout.CENTER);
  jbtShowTable_actionPerformed(null);
  
 }

 private void initializeDB() {
  try {
   Class.forName("com.mysql.jdbc.Driver");
   Connection connection = DriverManager.getConnection("jdbc:mysql://localhost/javabook", "root", "root");
   statement = connection.createStatement();
   DatabaseMetaData dbMetaData = connection.getMetaData();
      ResultSet rsTables = dbMetaData.getTables(null, null, null, new String[] {"TABLE"});
      while (rsTables.next()) {
       tableNames.add(rsTables.getString("TABLE_NAME"));
      }
      
  } catch (Exception ex) {
   ex.printStackTrace();
  }
 }

 private void jbtShowTable_actionPerformed(ActionEvent e) {
  try {
   ResultSet rset = statement.executeQuery("select * from " + jComboBox.getItemAt(jComboBox.getSelectedIndex()) + ";");
   jTextArea.setText("");
   
   ResultSetMetaData rsMetaData = rset.getMetaData();
   for (int i = 1; i <= rsMetaData.getColumnCount(); i++) {
    jTextArea.append(String.format("%-25s", rsMetaData.getColumnName(i)));
   }
   jTextArea.append("\n");
       
   while (rset.next()) {
    for (int i = 1; i <= rsMetaData.getColumnCount(); i++) {
     jTextArea.append(String.format("%-25s",rset.getString(i)));
    }
    jTextArea.append("\n");
   }
  } catch (SQLException ex) {
   JOptionPane.showMessageDialog(null, ex.getMessage(), "Error", JOptionPane.ERROR_MESSAGE);
  }
 }

 /** Main method */
 public static void main(String[] args) {
  Exercise06 applet = new Exercise06();
  JFrame frame = new JFrame();
  frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
  frame.setTitle("Exercise06");
  frame.getContentPane().add(applet, BorderLayout.CENTER);
  applet.init();
  applet.start();
  frame.setSize(800, 800);
  frame.setLocationRelativeTo(null); // Center the frame
  frame.setVisible(true);
 }
}

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