Mega Code Archive
This program computes the message digest of a file or the contents of a text area
<![CDATA[
/*
This program is a part of the companion code for Core Java 8th ed.
(http://horstmann.com/corejava)
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
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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.BorderLayout;
import java.awt.Container;
import java.awt.EventQueue;
import java.awt.Font;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import javax.swing.ButtonGroup;
import javax.swing.JFileChooser;
import javax.swing.JFrame;
import javax.swing.JMenu;
import javax.swing.JMenuBar;
import javax.swing.JMenuItem;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
import javax.swing.JRadioButton;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
import javax.swing.JTextField;
/**
* This program computes the message digest of a file or the contents of a text area.
* @version 1.13 2007-10-06
* @author Cay Horstmann
*/
public class MessageDigestTest
{
public static void main(String[] args)
{
EventQueue.invokeLater(new Runnable()
{
public void run()
{
JFrame frame = new MessageDigestFrame();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setVisible(true);
}
});
}
}
/**
* This frame contains a menu for computing the message digest of a file or text area, radio buttons
* to toggle between SHA-1 and MD5, a text area, and a text field to show the messge digest.
*/
class MessageDigestFrame extends JFrame
{
public MessageDigestFrame()
{
setTitle("MessageDigestTest");
setSize(DEFAULT_WIDTH, DEFAULT_HEIGHT);
JPanel panel = new JPanel();
ButtonGroup group = new ButtonGroup();
addRadioButton(panel, "SHA-1", group);
addRadioButton(panel, "MD5", group);
add(panel, BorderLayout.NORTH);
add(new JScrollPane(message), BorderLayout.CENTER);
add(digest, BorderLayout.SOUTH);
digest.setFont(new Font("Monospaced", Font.PLAIN, 12));
setAlgorithm("SHA-1");
JMenuBar menuBar = new JMenuBar();
JMenu menu = new JMenu("File");
JMenuItem fileDigestItem = new JMenuItem("File digest");
fileDigestItem.addActionListener(new ActionListener()
{
public void actionPerformed(ActionEvent event)
{
loadFile();
}
});
menu.add(fileDigestItem);
JMenuItem textDigestItem = new JMenuItem("Text area digest");
textDigestItem.addActionListener(new ActionListener()
{
public void actionPerformed(ActionEvent event)
{
String m = message.getText();
computeDigest(m.getBytes());
}
});
menu.add(textDigestItem);
menuBar.add(menu);
setJMenuBar(menuBar);
}
/**
* Adds a radio button to select an algorithm.
* @param c the container into which to place the button
* @param name the algorithm name
* @param g the button group
*/
public void addRadioButton(Container c, final String name, ButtonGroup g)
{
ActionListener listener = new ActionListener()
{
public void actionPerformed(ActionEvent event)
{
setAlgorithm(name);
}
};
JRadioButton b = new JRadioButton(name, g.getButtonCount() == 0);
c.add(b);
g.add(b);
b.addActionListener(listener);
}
/**
* Sets the algorithm used for computing the digest.
* @param alg the algorithm name
*/
public void setAlgorithm(String alg)
{
try
{
currentAlgorithm = MessageDigest.getInstance(alg);
digest.setText("");
}
catch (NoSuchAlgorithmException e)
{
digest.setText("" + e);
}
}
/**
* Loads a file and computes its message digest.
*/
public void loadFile()
{
JFileChooser chooser = new JFileChooser();
chooser.setCurrentDirectory(new File("."));
int r = chooser.showOpenDialog(this);
if (r == JFileChooser.APPROVE_OPTION)
{
try
{
String name = chooser.getSelectedFile().getAbsolutePath();
computeDigest(loadBytes(name));
}
catch (IOException e)
{
JOptionPane.showMessageDialog(null, e);
}
}
}
/**
* Loads the bytes in a file.
* @param name the file name
* @return an array with the bytes in the file
*/
public byte[] loadBytes(String name) throws IOException
{
FileInputStream in = null;
in = new FileInputStream(name);
try
{
ByteArrayOutputStream buffer = new ByteArrayOutputStream();
int ch;
while ((ch = in.read()) != -1)
buffer.write(ch);
return buffer.toByteArray();
}
finally
{
in.close();
}
}
/**
* Computes the message digest of an array of bytes and displays it in the text field.
* @param b the bytes for which the message digest should be computed.
*/
public void computeDigest(byte[] b)
{
currentAlgorithm.reset();
currentAlgorithm.update(b);
byte[] hash = currentAlgorithm.digest();
String d = "";
for (int i = 0; i < hash.length; i++)
{
int v = hash[i] & 0xFF;
if (v < 16) d += "0";
d += Integer.toString(v, 16).toUpperCase() + " ";
}
digest.setText(d);
}
private JTextArea message = new JTextArea();
private JTextField digest = new JTextField();
private MessageDigest currentAlgorithm;
private static final int DEFAULT_WIDTH = 400;
private static final int DEFAULT_HEIGHT = 300;
}
]]>