MessageDigestTest.java Source code

Introduction

Here is the source code for MessageDigestTest.java

Source

/*
   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;
}