A modification of the image viewer program that logs various events : Log « Language Basics « Java

A modification of the image viewer program that logs various events

   This program is a part of the companion code for Core Java 8th ed.

   This program is free software: you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation, either version 3 of the License, or
   (at your option) any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program.  If not, see <http://www.gnu.org/licenses/>.

import java.awt.EventQueue;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.File;
import java.io.IOException;
import java.io.OutputStream;
import java.util.logging.FileHandler;
import java.util.logging.Handler;
import java.util.logging.Level;
import java.util.logging.LogRecord;
import java.util.logging.Logger;
import java.util.logging.StreamHandler;

import javax.swing.ImageIcon;
import javax.swing.JFileChooser;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JMenu;
import javax.swing.JMenuBar;
import javax.swing.JMenuItem;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;

 * A modification of the image viewer program that logs various events.
 * @version 1.02 2007-05-31
 * @author Cay Horstmann
public class LoggingImageViewer
   public static void main(String[] args)
      if (System.getProperty("java.util.logging.config.class") == null
            && System.getProperty("java.util.logging.config.file") == null)
            final int LOG_ROTATION_COUNT = 10;
            Handler handler = new FileHandler("%h/LoggingImageViewer.log", 0, LOG_ROTATION_COUNT);
         catch (IOException e)
                  "Can't create log file handler", e);

      EventQueue.invokeLater(new Runnable()
            public void run()
               Handler windowHandler = new WindowHandler();

               JFrame frame = new ImageViewerFrame();

               Logger.getLogger("com.horstmann.corejava").fine("Showing frame");

 * The frame that shows the image.
class ImageViewerFrame extends JFrame
   public ImageViewerFrame()
      logger.entering("ImageViewerFrame", "<init>");

      // set up menu bar
      JMenuBar menuBar = new JMenuBar();

      JMenu menu = new JMenu("File");

      JMenuItem openItem = new JMenuItem("Open");
      openItem.addActionListener(new FileOpenListener());

      JMenuItem exitItem = new JMenuItem("Exit");
      exitItem.addActionListener(new ActionListener()
            public void actionPerformed(ActionEvent event)

      // use a label to display the images
      label = new JLabel();
      logger.exiting("ImageViewerFrame", "<init>");

   private class FileOpenListener implements ActionListener
      public void actionPerformed(ActionEvent event)
         logger.entering("ImageViewerFrame.FileOpenListener", "actionPerformed", event);

         // set up file chooser
         JFileChooser chooser = new JFileChooser();
         chooser.setCurrentDirectory(new File("."));

         // accept all files ending with .gif
         chooser.setFileFilter(new javax.swing.filechooser.FileFilter()
               public boolean accept(File f)
                  return f.getName().toLowerCase().endsWith(".gif") || f.isDirectory();

               public String getDescription()
                  return "GIF Images";

         // show file chooser dialog
         int r = chooser.showOpenDialog(ImageViewerFrame.this);

         // if image file accepted, set it as icon of the label
         if (r == JFileChooser.APPROVE_OPTION)
            String name = chooser.getSelectedFile().getPath();
            logger.log(Level.FINE, "Reading file {0}", name);
            label.setIcon(new ImageIcon(name));
         else logger.fine("File open dialog canceled.");
         logger.exiting("ImageViewerFrame.FileOpenListener", "actionPerformed");

   private JLabel label;
   private static Logger logger = Logger.getLogger("com.horstmann.corejava");
   private static final int DEFAULT_WIDTH = 300;
   private static final int DEFAULT_HEIGHT = 400;   

 * A handler for displaying log records in a window.
class WindowHandler extends StreamHandler
   public WindowHandler()
      frame = new JFrame();
      final JTextArea output = new JTextArea();
      frame.setSize(200, 200);
      frame.add(new JScrollPane(output));
      setOutputStream(new OutputStream()
            public void write(int b)
            } // not called

            public void write(byte[] b, int off, int len)
               output.append(new String(b, off, len));

   public void publish(LogRecord record)
      if (!frame.isVisible()) return;

   private JFrame frame;


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