Как создать почтовый клиент на Java, Email Client

В этой статье будет подробно рассмотрен пример отправки и приема писем и реализация почтового клиента написанного на java.. Вам понадобится javamail API для компиляции этого примера. Вы можете скачать его здесь.

Пример содержит следующие файлы/классы:

EmailClient: основной класс для клиентского приложения электронной почты
ConnectDialog: этот класс отображает диалоговое окно для ввода электронной почты сервер подключения.
MessagesTableModel: этот класс управляет электронной таблицей данных.
MessageDialog: этот класс отображает диалоговое окно используется для создания сообщения.
DownloadingDialog: этот класс отображает простое диалоговое окно с инструкциями пользователя, о том что сообщения загружаются.

Код достаточно большой но в нем имеются комментарии по описанию email client java. Содержание классов описаны ниже:

import java.awt.*;
import java.awt.event.*;
import java.net.*;
import java.util.*;
import javax.mail.*;
import javax.mail.internet.*;
import javax.swing.*;
import javax.swing.event.*;
 
// The E-mail Client.
public class EmailClient extends JFrame {
     
    // Message table's data model.
    private MessagesTableModel tableModel;
     
    // Table listing messages.
    private JTable table;
     
    // This the text area for displaying messages.
    private JTextArea messageTextArea;
     
  /* This is the split panel that holds the messages
     table and the message view panel. */
    private JSplitPane splitPane;
     
    // These are the buttons for managing the selected message.
    private JButton replyButton, forwardButton, deleteButton;
     
    // Currently selected message in table.
    private Message selectedMessage;
     
    // Flag for whether or not a message is being deleted.
    private boolean deleting;
     
    // This is the JavaMail session.
    private Session session;
     
    // Constructor for E-mail Client.
    public EmailClient() {
        // Set application title.
        setTitle("E-mail Client");
         
        // Set window size.
        setSize(640, 480);
         
        // Handle window closing events.
        addWindowListener(new WindowAdapter() {
            public void windowClosing(WindowEvent e) {
                actionExit();
            }
        });
         
        // Setup file menu.
        JMenuBar menuBar = new JMenuBar();
        JMenu fileMenu = new JMenu("File");
        fileMenu.setMnemonic(KeyEvent.VK_F);
        JMenuItem fileExitMenuItem = new JMenuItem("Exit",
                KeyEvent.VK_X);
        fileExitMenuItem.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                actionExit();
            }
        });
        fileMenu.add(fileExitMenuItem);
        menuBar.add(fileMenu);
        setJMenuBar(menuBar);
         
        // Setup buttons panel.
        JPanel buttonPanel = new JPanel();
        JButton newButton = new JButton("New Message");
        newButton.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                actionNew();
            }
        });
        buttonPanel.add(newButton);
         
        // Setup messages table.
        tableModel = new MessagesTableModel();
        table = new JTable(tableModel);
        table.getSelectionModel().addListSelectionListener(new
                ListSelectionListener() {
            public void valueChanged(ListSelectionEvent e) {
                tableSelectionChanged();
            }
        });
        // Allow only one row at a time to be selected.
        table.setSelectionMode(ListSelectionModel.SINGLE_SELECTION);
         
        // Setup E-mails panel.
        JPanel emailsPanel = new JPanel();
        emailsPanel.setBorder(
                BorderFactory.createTitledBorder("E-mails"));
        messageTextArea = new JTextArea();
        messageTextArea.setEditable(false);
        splitPane = new JSplitPane(JSplitPane.VERTICAL_SPLIT,
                new JScrollPane(table), new JScrollPane(messageTextArea));
        emailsPanel.setLayout(new BorderLayout());
        emailsPanel.add(splitPane, BorderLayout.CENTER);
         
        // Setup buttons panel 2.
        JPanel buttonPanel2 = new JPanel();
        replyButton = new JButton("Reply");
        replyButton.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                actionReply();
            }
        });
        replyButton.setEnabled(false);
        buttonPanel2.add(replyButton);
        forwardButton = new JButton("Forward");
        forwardButton.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                actionForward();
            }
        });
        forwardButton.setEnabled(false);
        buttonPanel2.add(forwardButton);
        deleteButton = new JButton("Delete");
        deleteButton.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                actionDelete();
            }
        });
        deleteButton.setEnabled(false);
        buttonPanel2.add(deleteButton);
         
        // Add panels to display.
        getContentPane().setLayout(new BorderLayout());
        getContentPane().add(buttonPanel, BorderLayout.NORTH);
        getContentPane().add(emailsPanel, BorderLayout.CENTER);
        getContentPane().add(buttonPanel2, BorderLayout.SOUTH);
    }
     
    // Exit this program.
    private void actionExit() {
        System.exit(0);
    }
     
    // Create a new message.
    private void actionNew() {
        sendMessage(MessageDialog.NEW, null);
    }
     
    // Called when table row selection changes.
    private void tableSelectionChanged() {
    /* If not in the middle of deleting a message, set
       the selected message and display it. */
        if (!deleting) {
            selectedMessage =
                    tableModel.getMessage(table.getSelectedRow());
            showSelectedMessage();
            updateButtons();
        }
    }
     
    // Reply to a message.
    private void actionReply() {
        sendMessage(MessageDialog.REPLY, selectedMessage);
    }
     
    // Forward a message.
    private void actionForward() {
        sendMessage(MessageDialog.FORWARD, selectedMessage);
    }
     
    // Delete the selected message.
    private void actionDelete() {
        deleting = true;
         
        try {
            // Delete message from server.
            selectedMessage.setFlag(Flags.Flag.DELETED, true);
            Folder folder = selectedMessage.getFolder();
            folder.close(true);
            folder.open(Folder.READ_WRITE);
        } catch (Exception e) {
            showError("Unable to delete message.", false);
        }
         
        // Delete message from table.
        tableModel.deleteMessage(table.getSelectedRow());
         
        // Update GUI.
        messageTextArea.setText("");
        deleting = false;
        selectedMessage = null;
        updateButtons();
    }
     
    // Send the specified message.
    private void sendMessage(int type, Message message) {
        // Display message dialog to get message values.
        MessageDialog dialog;
        try {
            dialog = new MessageDialog(this, type, message);
            if (!dialog.display()) {
                // Return if dialog was cancelled.
                return;
            }
        } catch (Exception e) {
            showError("Unable to send message.", false);
            return;
        }
         
        try {
            // Create a new message with values from dialog.
            Message newMessage = new MimeMessage(session);
            newMessage.setFrom(new InternetAddress(dialog.getFrom()));
            newMessage.setRecipient(Message.RecipientType.TO,
                    new InternetAddress(dialog.getTo()));
            newMessage.setSubject(dialog.getSubject());
            newMessage.setSentDate(new Date());
            newMessage.setText(dialog.getContent());
             
            // Send new message.
            Transport.send(newMessage);
        } catch (Exception e) {
            showError("Unable to send message.", false);
        }
    }
     
    // Show the selected message in the content panel.
    private void showSelectedMessage() {
        // Show hour glass cursor while message is loaded.
        setCursor(Cursor.getPredefinedCursor(Cursor.WAIT_CURSOR));
        try {
            messageTextArea.setText(
                    getMessageContent(selectedMessage));
            messageTextArea.setCaretPosition(0);
        } catch (Exception e) {
            showError("Unabled to load message.", false);
        } finally {
            // Return to default cursor.
            setCursor(Cursor.getDefaultCursor());
        }
    }
     
  /* Update each button's state based off of whether or not
     there is a message currently selected in the table. */
    private void updateButtons() {
        if (selectedMessage != null) {
            replyButton.setEnabled(true);
            forwardButton.setEnabled(true);
            deleteButton.setEnabled(true);
        } else {
            replyButton.setEnabled(false);
            forwardButton.setEnabled(false);
            deleteButton.setEnabled(false);
        }
    }
     
    // Show the application window on the screen.
    public void show() {
        super.show();
         
        // Update the split panel to be divided 50/50.
        splitPane.setDividerLocation(.5);
    }
     
    // Connect to e-mail server.
    public void connect() {
        // Display connect dialog.
        ConnectDialog dialog = new ConnectDialog(this);
        dialog.show();
         
        // Build connection URL from connect dialog settings.
        StringBuffer connectionUrl = new StringBuffer();
        connectionUrl.append(dialog.getType() + "://");
        connectionUrl.append(dialog.getUsername() + ":");
        connectionUrl.append(dialog.getPassword() + "@");
        connectionUrl.append(dialog.getServer() + "/");
         
    /* Display dialog stating that messages are
       currently being downloaded from server. */
        final DownloadingDialog downloadingDialog =
                new DownloadingDialog(this);
        SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                downloadingDialog.show();
            }
        });
         
        // Establish JavaMail session and connect to server.
        Store store = null;
        try {
            // Initialize JavaMail session with SMTP server.
            Properties props = new Properties();
            props.put("mail.smtp.host", dialog.getSmtpServer());
            session = Session.getDefaultInstance(props, null);
             
            // Connect to e-mail server.
            URLName urln = new URLName(connectionUrl.toString());
            store = session.getStore(urln);
            store.connect();
        } catch (Exception e) {
            // Close the downloading dialog.
            downloadingDialog.dispose();
             
            // Show error dialog.
            showError("Unable to connect.", true);
        }
         
        // Download message headers from server.
        try {
            // Open main "INBOX" folder.
            Folder folder = store.getFolder("INBOX");
            folder.open(Folder.READ_WRITE);
             
            // Get folder's list of messages.
            Message[] messages = folder.getMessages();
             
            // Retrieve message headers for each message in folder.
            FetchProfile profile = new FetchProfile();
 
            profile.add(FetchProfile.Item.ENVELOPE);
            folder.fetch(messages, profile);
             
            // Put messages in table.
            tableModel.setMessages(messages);
        } catch (Exception e) {
            // Close the downloading dialog.
            downloadingDialog.dispose();
             
            // Show error dialog.
            showError("Unable to download messages.", true);
        }
         
        // Close the downloading dialog.
        downloadingDialog.dispose();
    }
     
    // Show error dialog and exit afterwards if necessary.
    private void showError(String message, boolean exit) {
        JOptionPane.showMessageDialog(this, message, "Error",
                JOptionPane.ERROR_MESSAGE);
        if (exit)
            System.exit(0);
    }
     
    // Get a message's content.
    public static String getMessageContent(Message message)
    throws Exception {
        Object content = message.getContent();
        if (content instanceof Multipart) {
            StringBuffer messageContent = new StringBuffer();
            Multipart multipart = (Multipart) content;
            for (int i = 0; i < multipart.getCount(); i++) {
                Part part = (Part) multipart.getBodyPart(i);
                if (part.isMimeType("text/plain")) {
                    messageContent.append(part.getContent().toString());
                }
            }
            return messageContent.toString();
        } else {
            return content.toString();
        }
    }
     
    // Run the E-mail Client.
    public static void main(String[] args) {
        EmailClient client = new EmailClient();
        client.show();
         
        // Display connect dialog.
        client.connect();
    }
}
 
ConnectDialog:
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
 
/* This class displays a dialog for entering e-mail
   server connection settings. */
public class ConnectDialog extends JDialog {
     
    // These are the e-mail server types.
    private static final String[] TYPES = {"pop3", "imap"};
     
    // Combo box for e-mail server types.
    private JComboBox typeComboBox;
     
    // Server, username and SMTP server text fields.
    private JTextField serverTextField, usernameTextField;
    private JTextField smtpServerTextField;
     
    // Password text field.
    private JPasswordField passwordField;
     
    // Constructor for dialog.
    public ConnectDialog(Frame parent) {
        // Call super constructor, specifying that dialog is modal.
        super(parent, true);
         
        // Set dialog title.
        setTitle("Connect");
         
        // Handle closing events.
        addWindowListener(new WindowAdapter() {
            public void windowClosing(WindowEvent e) {
                actionCancel();
            }
        });
         
        // Setup settings panel.
        JPanel settingsPanel = new JPanel();
        settingsPanel.setBorder(
                BorderFactory.createTitledBorder("Connection Settings"));
        GridBagConstraints constraints;
        GridBagLayout layout = new GridBagLayout();
        settingsPanel.setLayout(layout);
        JLabel typeLabel = new JLabel("Type:");
        constraints = new GridBagConstraints();
        constraints.anchor = GridBagConstraints.EAST;
        constraints.insets = new Insets(5, 5, 0, 0);
        layout.setConstraints(typeLabel, constraints);
        settingsPanel.add(typeLabel);
        typeComboBox = new JComboBox(TYPES);
        constraints = new GridBagConstraints();
        constraints.anchor = GridBagConstraints.WEST;
        constraints.gridwidth = GridBagConstraints.REMAINDER;
        constraints.insets = new Insets(5, 5, 0, 5);
        constraints.weightx = 1.0D;
        layout.setConstraints(typeComboBox, constraints);
        settingsPanel.add(typeComboBox);
        JLabel serverLabel = new JLabel("Server:");
        constraints = new GridBagConstraints();
        constraints.anchor = GridBagConstraints.EAST;
        constraints.insets = new Insets(5, 5, 0, 0);
        layout.setConstraints(serverLabel, constraints);
        settingsPanel.add(serverLabel);
        serverTextField = new JTextField(25);
        constraints = new GridBagConstraints();
        constraints.gridwidth = GridBagConstraints.REMAINDER;
        constraints.insets = new Insets(5, 5, 0, 5);
        constraints.weightx = 1.0D;
        layout.setConstraints(serverTextField, constraints);
        settingsPanel.add(serverTextField);
        JLabel usernameLabel = new JLabel("Username:");
        constraints = new GridBagConstraints();
        constraints.anchor = GridBagConstraints.EAST;
        constraints.insets = new Insets(5, 5, 0, 0);
        layout.setConstraints(usernameLabel, constraints);
        settingsPanel.add(usernameLabel);
        usernameTextField = new JTextField();
        constraints = new GridBagConstraints();
        constraints.anchor = GridBagConstraints.WEST;
        constraints.fill = GridBagConstraints.HORIZONTAL;
        constraints.gridwidth = GridBagConstraints.REMAINDER;
        constraints.insets = new Insets(5, 5, 0, 5);
        constraints.weightx = 1.0D;
        layout.setConstraints(usernameTextField, constraints);
        settingsPanel.add(usernameTextField);
        JLabel passwordLabel = new JLabel("Password:");
        constraints = new GridBagConstraints();
        constraints.anchor = GridBagConstraints.EAST;
        constraints.insets = new Insets(5, 5, 5, 0);
        layout.setConstraints(passwordLabel, constraints);
        settingsPanel.add(passwordLabel);
        passwordField = new JPasswordField();
        constraints = new GridBagConstraints();
        constraints.anchor = GridBagConstraints.WEST;
        constraints.fill = GridBagConstraints.HORIZONTAL;
        constraints.gridwidth = GridBagConstraints.REMAINDER;
        constraints.insets = new Insets(5, 5, 5, 5);
        constraints.weightx = 1.0D;
        layout.setConstraints(passwordField, constraints);
        settingsPanel.add(passwordField);
        JLabel smtpServerLabel = new JLabel("SMTP Server:");
        constraints = new GridBagConstraints();
        constraints.anchor = GridBagConstraints.EAST;
        constraints.insets = new Insets(5, 5, 5, 0);
        layout.setConstraints(smtpServerLabel, constraints);
        settingsPanel.add(smtpServerLabel);
        smtpServerTextField = new JTextField(25);
        constraints = new GridBagConstraints();
        constraints.gridwidth = GridBagConstraints.REMAINDER;
        constraints.insets = new Insets(5, 5, 5, 5);
        constraints.weightx = 1.0D;
        layout.setConstraints(smtpServerTextField, constraints);
        settingsPanel.add(smtpServerTextField);
         
        // Setup buttons panel.
        JPanel buttonsPanel = new JPanel();
        JButton connectButton = new JButton("Connect");
        connectButton.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                actionConnect();
            }
        });
        buttonsPanel.add(connectButton);
        JButton cancelButton = new JButton("Cancel");
        cancelButton.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                actionCancel();
            }
        });
        buttonsPanel.add(cancelButton);
         
        // Add panels to display.
        getContentPane().setLayout(new BorderLayout());
        getContentPane().add(settingsPanel, BorderLayout.CENTER);
        getContentPane().add(buttonsPanel, BorderLayout.SOUTH);
         
        // Size dialog to components.
        pack();
         
        // Center dialog over application.
        setLocationRelativeTo(parent);
    }
     
    // Validate connection settings and close dialog.
    private void actionConnect() {
        if (serverTextField.getText().trim().length() < 1
                || usernameTextField.getText().trim().length() < 1
                || passwordField.getPassword().length < 1
                || smtpServerTextField.getText().trim().length() < 1) {
            JOptionPane.showMessageDialog(this,
                    "One or more settings is missing.",
                    "Missing Setting(s)", JOptionPane.ERROR_MESSAGE);
            return;
        }
         
        // Close dialog.
        dispose();
    }
     
    // Cancel connecting and exit program.
    private void actionCancel() {
        System.exit(0);
    }
     
    // Get e-mail server type.
    public String getType() {
        return (String) typeComboBox.getSelectedItem();
    }
     
    // Get e-mail server.
    public String getServer() {
        return serverTextField.getText();
    }
     
    // Get e-mail username.
    public String getUsername() {
        return usernameTextField.getText();
    }
     
    // Get e-mail password.
    public String getPassword() {
        return new String(passwordField.getPassword());
    }
     
    // Get e-mail SMTP server.
    public String getSmtpServer() {
        return smtpServerTextField.getText();
    }
}
MessagesTableModel:

import java.util.*;
import javax.mail.*;
import javax.swing.*;
import javax.swing.table.*;
 
// This class manages the e-mail table's data.
public class MessagesTableModel extends AbstractTableModel {
     
    // These are the names for the table's columns.
    private static final String[] columnNames = {"Sender",
    "Subject", "Date"};
     
    // The table's list of messages.
    private ArrayList messageList = new ArrayList();
     
    // Sets the table's list of messages.
    public void setMessages(Message[] messages) {
        for (int i = messages.length - 1; i >= 0; i--) {
            messageList.add(messages[i]);
        }
         
        // Fire table data change notification to table.
        fireTableDataChanged();
    }
     
    // Get a message for the specified row.
    public Message getMessage(int row) {
        return (Message) messageList.get(row);
    }
     
    // Remove a message from the list.
    public void deleteMessage(int row) {
        messageList.remove(row);
         
        // Fire table row deletion notification to table.
        fireTableRowsDeleted(row, row);
    }
     
    // Get table's column count.
    public int getColumnCount() {
        return columnNames.length;
    }
     
    // Get a column's name.
    public String getColumnName(int col) {
        return columnNames[col];
    }
     
    // Get table's row count.
    public int getRowCount() {
        return messageList.size();
    }
     
    // Get value for a specific row and column combination.
    public Object getValueAt(int row, int col) {
        try {
            Message message = (Message) messageList.get(row);
            switch (col) {
                case 0: // Sender
                    Address[] senders = message.getFrom();
                    if (senders != null || senders.length > 0) {
                        return senders[0].toString();
                    } else {
                        return "[none]";
                    }
                case 1: // Subject
                    String subject = message.getSubject();
                    if (subject != null && subject.length() > 0) {
                        return subject;
                    } else {
                        return "[none]";
                    }
                case 2: // Date
                    Date date = message.getSentDate();
                    if (date != null) {
                        return date.toString();
                    } else {
                        return "[none]";
                    }
            }
        } catch (Exception e) {
            // Fail silently.
            return "";
        }
         
        return "";
    }
}
 
MessageDialog:
import java.awt.*;
import java.awt.event.*;
import javax.mail.*;
import javax.swing.*;
 
// This class displays the dialog used for creating messages.
public class MessageDialog extends JDialog {
     
    // Dialog message identifiers.
    public static final int NEW = 0;
    public static final int REPLY = 1;
    public static final int FORWARD = 2;
     
    // Message from, to and subject text fields.
    private JTextField fromTextField, toTextField;
    private JTextField subjectTextField;
     
    // Message content text area.
    private JTextArea contentTextArea;
     
    // Flag specifying whether or not dialog was cancelled.
    private boolean cancelled;
     
    // Constructor for dialog.
    public MessageDialog(Frame parent, int type, Message message)
    throws Exception {
        // Call super constructor, specifying that dialog is modal.
        super(parent, true);
         
    /* Set dialog title and get message's "to", "subject"
       and "content" values based on message type. */
        String to = "", subject = "", content = "";
        switch (type) {
            // Reply message.
            case REPLY:
                setTitle("Reply To Message");
                 
                // Get message "to" value
                Address[] senders = message.getFrom();
                if (senders != null || senders.length > 0) {
                    to = senders[0].toString();
                }
                to = message.getFrom()[0].toString();
                 
                // Get message subject.
                subject = message.getSubject();
                if (subject != null && subject.length() > 0) {
                    subject = "RE: " + subject;
                } else {
                    subject = "RE:";
                }
                 
                // Get message content and add "REPLIED TO" notation.
                content = "\n----------------- " +
                        "REPLIED TO MESSAGE" +
                        " -----------------\n" +
                        EmailClient.getMessageContent(message);
                break;
                 
                // Forward message.
            case FORWARD:
                setTitle("Forward Message");
                 
                // Get message subject.
                subject = message.getSubject();
                if (subject != null && subject.length() > 0) {
                    subject = "FWD: " + subject;
                } else {
                    subject = "FWD:";
                }
                 
                // Get message content and add "FORWARDED" notation.
                content = "\n----------------- " +
                        "FORWARDED MESSAGE" +
                        " -----------------\n" +
                        EmailClient.getMessageContent(message);
                break;
                 
                // New message.
            default:
                setTitle("New Message");
        }
         
        // Handle closing events.
        addWindowListener(new WindowAdapter() {
            public void windowClosing(WindowEvent e) {
                actionCancel();
            }
        });
         
        // Setup fields panel.
        JPanel fieldsPanel = new JPanel();
        GridBagConstraints constraints;
        GridBagLayout layout = new GridBagLayout();
        fieldsPanel.setLayout(layout);
        JLabel fromLabel = new JLabel("From:");
        constraints = new GridBagConstraints();
        constraints.anchor = GridBagConstraints.EAST;
        constraints.insets = new Insets(5, 5, 0, 0);
        layout.setConstraints(fromLabel, constraints);
        fieldsPanel.add(fromLabel);
        fromTextField = new JTextField();
        constraints = new GridBagConstraints();
        constraints.fill = GridBagConstraints.HORIZONTAL;
        constraints.gridwidth = GridBagConstraints.REMAINDER;
        constraints.insets = new Insets(5, 5, 0, 0);
        layout.setConstraints(fromTextField, constraints);
        fieldsPanel.add(fromTextField);
        JLabel toLabel = new JLabel("To:");
        constraints = new GridBagConstraints();
        constraints.anchor = GridBagConstraints.EAST;
        constraints.insets = new Insets(5, 5, 0, 0);
        layout.setConstraints(toLabel, constraints);
        fieldsPanel.add(toLabel);
        toTextField = new JTextField(to);
        constraints = new GridBagConstraints();
        constraints.fill = GridBagConstraints.HORIZONTAL;
        constraints.gridwidth = GridBagConstraints.REMAINDER;
        constraints.insets = new Insets(5, 5, 0, 0);
        constraints.weightx = 1.0D;
        layout.setConstraints(toTextField, constraints);
        fieldsPanel.add(toTextField);
        JLabel subjectLabel = new JLabel("Subject:");
        constraints = new GridBagConstraints();
        constraints.insets = new Insets(5, 5, 5, 0);
        layout.setConstraints(subjectLabel, constraints);
        fieldsPanel.add(subjectLabel);
        subjectTextField = new JTextField(subject);
        constraints = new GridBagConstraints();
        constraints.fill = GridBagConstraints.HORIZONTAL;
        constraints.gridwidth = GridBagConstraints.REMAINDER;
        constraints.insets = new Insets(5, 5, 5, 0);
        layout.setConstraints(subjectTextField, constraints);
        fieldsPanel.add(subjectTextField);
         
        // Setup content panel.
        JScrollPane contentPanel = new JScrollPane();
        contentTextArea = new JTextArea(content, 10, 50);
        contentPanel.setViewportView(contentTextArea);
         
        // Setup buttons panel.
        JPanel buttonsPanel = new JPanel();
        JButton sendButton = new JButton("Send");
        sendButton.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                actionSend();
            }
        });
        buttonsPanel.add(sendButton);
        JButton cancelButton = new JButton("Cancel");
        cancelButton.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                actionCancel();
            }
        });
        buttonsPanel.add(cancelButton);
         
        // Add panels to display.
        getContentPane().setLayout(new BorderLayout());
        getContentPane().add(fieldsPanel, BorderLayout.NORTH);
        getContentPane().add(contentPanel, BorderLayout.CENTER);
        getContentPane().add(buttonsPanel, BorderLayout.SOUTH);
         
        // Size dialog to components.
        pack();
         
        // Center dialog over application.
        setLocationRelativeTo(parent);
    }
     
    // Validate message fields and close dialog.
    private void actionSend() {
        if (fromTextField.getText().trim().length() < 1
                || toTextField.getText().trim().length() < 1
                || subjectTextField.getText().trim().length() < 1
                || contentTextArea.getText().trim().length() < 1) {
            JOptionPane.showMessageDialog(this,
                    "One or more fields is missing.",
                    "Missing Field(s)", JOptionPane.ERROR_MESSAGE);
            return;
        }
         
        // Close dialog.
        dispose();
    }
     
    // Cancel creating this message and close dialog.
    private void actionCancel() {
        cancelled = true;
         
        // Close dialog.
        dispose();
    }
     
    // Show dialog.
    public boolean display() {
        show();
         
        // Return whether or not display was successful.
        return !cancelled;
    }
     
    // Get message's "From" field value.
    public String getFrom() {
        return fromTextField.getText();
    }
     
    // Get message's "To" field value.
    public String getTo() {
        return toTextField.getText();
    }
     
    // Get message's "Subject" field value.
    public String getSubject() {
        return subjectTextField.getText();
    }
     
    // Get message's "content" field value.
    public String getContent() {
        return contentTextArea.getText();
    }
}
 
DownloadingDialog:
import java.awt.*;
import javax.swing.*;
 
/* This class displays a simple dialog instructing the user
   that messages are being downloaded. */
public class DownloadingDialog extends JDialog {
     
    // Constructor for dialog.
    public DownloadingDialog(Frame parent) {
        // Call super constructor, specifying that dialog is modal.
        super(parent, true);
         
        // Set dialog title.
        setTitle("E-mail Client");
         
        // Instruct window not to close when the "X" is clicked.
        setDefaultCloseOperation(DO_NOTHING_ON_CLOSE);
         
        // Put a message with a nice border in this dialog.
        JPanel contentPane = new JPanel();
        contentPane.setBorder(
                BorderFactory.createEmptyBorder(5, 5, 5, 5));
        contentPane.add(new JLabel("Downloading messages..."));
        setContentPane(contentPane);
         
        // Size dialog to components.
        pack();
         
        // Center dialog over application.
        setLocationRelativeTo(parent);
    }
}

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import java.awt.*;

import java.awt.event.*;

import java.net.*;

import java.util.*;

import javax.mail.*;

import javax.mail.internet.*;

import javax.swing.*;

import javax.swing.event.*;

// The E-mail Client.

public class EmailClient extends JFrame {

// Message table's data model.

private MessagesTableModel tableModel;

// Table listing messages.

private JTable table;

// This the text area for displaying messages.

private JTextArea messageTextArea;

/* This is the split panel that holds the messages

table and the message view panel. */

private JSplitPane splitPane;

// These are the buttons for managing the selected message.

private JButton replyButton, forwardButton, deleteButton;

// Currently selected message in table.

private Message selectedMessage;

// Flag for whether or not a message is being deleted.

private boolean deleting;

// This is the JavaMail session.

private Session session;

// Constructor for E-mail Client.

public EmailClient() {

// Set application title.

setTitle("E-mail Client");

// Set window size.

setSize(640, 480);

// Handle window closing events.

addWindowListener(new WindowAdapter() {

public void windowClosing(WindowEvent e) {

actionExit();

}

});

// Setup file menu.

JMenuBar menuBar = new JMenuBar();

JMenu fileMenu = new JMenu("File");

fileMenu.setMnemonic(KeyEvent.VK_F);

JMenuItem fileExitMenuItem = new JMenuItem("Exit",

KeyEvent.VK_X);

fileExitMenuItem.addActionListener(new ActionListener() {

public void actionPerformed(ActionEvent e) {

actionExit();

}

});

fileMenu.add(fileExitMenuItem);

menuBar.add(fileMenu);

setJMenuBar(menuBar);

// Setup buttons panel.

JPanel buttonPanel = new JPanel();

JButton newButton = new JButton("New Message");

newButton.addActionListener(new ActionListener() {

public void actionPerformed(ActionEvent e) {

actionNew();

}

});

buttonPanel.add(newButton);

// Setup messages table.

tableModel = new MessagesTableModel();

table = new JTable(tableModel);

table.getSelectionModel().addListSelectionListener(new

ListSelectionListener() {

public void valueChanged(ListSelectionEvent e) {

tableSelectionChanged();

}

});

// Allow only one row at a time to be selected.

table.setSelectionMode(ListSelectionModel.SINGLE_SELECTION);

// Setup E-mails panel.

JPanel emailsPanel = new JPanel();

emailsPanel.setBorder(

BorderFactory.createTitledBorder("E-mails"));

messageTextArea = new JTextArea();

messageTextArea.setEditable(false);

splitPane = new JSplitPane(JSplitPane.VERTICAL_SPLIT,

new JScrollPane(table), new JScrollPane(messageTextArea));

emailsPanel.setLayout(new BorderLayout());

emailsPanel.add(splitPane, BorderLayout.CENTER);

// Setup buttons panel 2.

JPanel buttonPanel2 = new JPanel();

replyButton = new JButton("Reply");

replyButton.addActionListener(new ActionListener() {

public void actionPerformed(ActionEvent e) {

actionReply();

}

});

replyButton.setEnabled(false);

buttonPanel2.add(replyButton);

forwardButton = new JButton("Forward");

forwardButton.addActionListener(new ActionListener() {

public void actionPerformed(ActionEvent e) {

actionForward();

}

});

forwardButton.setEnabled(false);

buttonPanel2.add(forwardButton);

deleteButton = new JButton("Delete");

deleteButton.addActionListener(new ActionListener() {

public void actionPerformed(ActionEvent e) {

actionDelete();

}

});

deleteButton.setEnabled(false);

buttonPanel2.add(deleteButton);

// Add panels to display.

getContentPane().setLayout(new BorderLayout());

getContentPane().add(buttonPanel, BorderLayout.NORTH);

getContentPane().add(emailsPanel, BorderLayout.CENTER);

getContentPane().add(buttonPanel2, BorderLayout.SOUTH);

}

// Exit this program.

private void actionExit() {

System.exit(0);

}

// Create a new message.

private void actionNew() {

sendMessage(MessageDialog.NEW, null);

}

// Called when table row selection changes.

private void tableSelectionChanged() {

/* If not in the middle of deleting a message, set

the selected message and display it. */

if (!deleting) {

selectedMessage =

tableModel.getMessage(table.getSelectedRow());

showSelectedMessage();

updateButtons();

}

// Reply to a message.

private void actionReply() {

sendMessage(MessageDialog.REPLY, selectedMessage);

}

// Forward a message.

private void actionForward() {

sendMessage(MessageDialog.FORWARD, selectedMessage);

}

// Delete the selected message.

private void actionDelete() {

deleting = true;

try {

// Delete message from server.

selectedMessage.setFlag(Flags.Flag.DELETED, true);

Folder folder = selectedMessage.getFolder();

folder.close(true);

folder.open(Folder.READ_WRITE);

} catch (Exception e) {

showError("Unable to delete message.", false);

}

// Delete message from table.

tableModel.deleteMessage(table.getSelectedRow());

// Update GUI.

messageTextArea.setText("");

deleting = false;

selectedMessage = null;

updateButtons();

}

// Send the specified message.

private void sendMessage(int type, Message message) {

// Display message dialog to get message values.

MessageDialog dialog;

try {

dialog = new MessageDialog(this, type, message);

if (!dialog.display()) {

// Return if dialog was cancelled.

return;

}

} catch (Exception e) {

showError("Unable to send message.", false);

return;

}

try {

// Create a new message with values from dialog.

Message newMessage = new MimeMessage(session);

newMessage.setFrom(new InternetAddress(dialog.getFrom()));

newMessage.setRecipient(Message.RecipientType.TO,

new InternetAddress(dialog.getTo()));

newMessage.setSubject(dialog.getSubject());

newMessage.setSentDate(new Date());

newMessage.setText(dialog.getContent());

// Send new message.

Transport.send(newMessage);

} catch (Exception e) {

showError("Unable to send message.", false);

}

// Show the selected message in the content panel.

private void showSelectedMessage() {

// Show hour glass cursor while message is loaded.

setCursor(Cursor.getPredefinedCursor(Cursor.WAIT_CURSOR));

try {

messageTextArea.setText(

getMessageContent(selectedMessage));

messageTextArea.setCaretPosition(0);

} catch (Exception e) {

showError("Unabled to load message.", false);

} finally {

// Return to default cursor.

setCursor(Cursor.getDefaultCursor());

}

/* Update each button's state based off of whether or not

there is a message currently selected in the table. */

private void updateButtons() {

if (selectedMessage != null) {

replyButton.setEnabled(true);

forwardButton.setEnabled(true);

deleteButton.setEnabled(true);

} else {

replyButton.setEnabled(false);

forwardButton.setEnabled(false);

deleteButton.setEnabled(false);

}

// Show the application window on the screen.

public void show() {

super.show();

// Update the split panel to be divided 50/50.

splitPane.setDividerLocation(.5);

}

// Connect to e-mail server.

public void connect() {

// Display connect dialog.

ConnectDialog dialog = new ConnectDialog(this);

dialog.show();

// Build connection URL from connect dialog settings.

StringBuffer connectionUrl = new StringBuffer();

connectionUrl.append(dialog.getType() + "://");

connectionUrl.append(dialog.getUsername() + ":");

connectionUrl.append(dialog.getPassword() + "@");

connectionUrl.append(dialog.getServer() + "/");

/* Display dialog stating that messages are

currently being downloaded from server. */

final DownloadingDialog downloadingDialog =

new DownloadingDialog(this);

SwingUtilities.invokeLater(new Runnable() {

public void run() {

downloadingDialog.show();

}

});

// Establish JavaMail session and connect to server.

Store store = null;

try {

// Initialize JavaMail session with SMTP server.

Properties props = new Properties();

props.put("mail.smtp.host", dialog.getSmtpServer());

session = Session.getDefaultInstance(props, null);

// Connect to e-mail server.

URLName urln = new URLName(connectionUrl.toString());

store = session.getStore(urln);

store.connect();

} catch (Exception e) {

// Close the downloading dialog.

downloadingDialog.dispose();

// Show error dialog.

showError("Unable to connect.", true);

}

// Download message headers from server.

try {

// Open main "INBOX" folder.

Folder folder = store.getFolder("INBOX");

folder.open(Folder.READ_WRITE);

// Get folder's list of messages.

Message[] messages = folder.getMessages();

// Retrieve message headers for each message in folder.

FetchProfile profile = new FetchProfile();

profile.add(FetchProfile.Item.ENVELOPE);

folder.fetch(messages, profile);

// Put messages in table.

tableModel.setMessages(messages);

} catch (Exception e) {

// Close the downloading dialog.

downloadingDialog.dispose();

// Show error dialog.

showError("Unable to download messages.", true);

}

// Close the downloading dialog.

downloadingDialog.dispose();

}

// Show error dialog and exit afterwards if necessary.

private void showError(String message, boolean exit) {

JOptionPane.showMessageDialog(this, message, "Error",

JOptionPane.ERROR_MESSAGE);

if (exit)

System.exit(0);

}

// Get a message's content.

public static String getMessageContent(Message message)

throws Exception {

Object content = message.getContent();

if (content instanceof Multipart) {

StringBuffer messageContent = new StringBuffer();

Multipart multipart = (Multipart) content;

for (int i = 0; i < multipart.getCount(); i++) {

Part part = (Part) multipart.getBodyPart(i);

if (part.isMimeType("text/plain")) {

messageContent.append(part.getContent().toString());

}

return messageContent.toString();

} else {

return content.toString();

}

// Run the E-mail Client.

public static void main(String[] args) {

EmailClient client = new EmailClient();

client.show();

// Display connect dialog.

client.connect();

}

ConnectDialog:

import java.awt.*;

import java.awt.event.*;

import javax.swing.*;

/* This class displays a dialog for entering e-mail

server connection settings. */

public class ConnectDialog extends JDialog {

// These are the e-mail server types.

private static final String[] TYPES = {"pop3", "imap"};

// Combo box for e-mail server types.

private JComboBox typeComboBox;

// Server, username and SMTP server text fields.

private JTextField serverTextField, usernameTextField;

private JTextField smtpServerTextField;

// Password text field.

private JPasswordField passwordField;

// Constructor for dialog.

public ConnectDialog(Frame parent) {

// Call super constructor, specifying that dialog is modal.

super(parent, true);

// Set dialog title.

setTitle("Connect");

// Handle closing events.

addWindowListener(new WindowAdapter() {

public void windowClosing(WindowEvent e) {

actionCancel();

}

});

// Setup settings panel.

JPanel settingsPanel = new JPanel();

settingsPanel.setBorder(

BorderFactory.createTitledBorder("Connection Settings"));

GridBagConstraints constraints;

GridBagLayout layout = new GridBagLayout();

settingsPanel.setLayout(layout);

JLabel typeLabel = new JLabel("Type:");

constraints = new GridBagConstraints();

constraints.anchor = GridBagConstraints.EAST;

constraints.insets = new Insets(5, 5, 0, 0);

layout.setConstraints(typeLabel, constraints);

settingsPanel.add(typeLabel);

typeComboBox = new JComboBox(TYPES);

constraints = new GridBagConstraints();

constraints.anchor = GridBagConstraints.WEST;

constraints.gridwidth = GridBagConstraints.REMAINDER;

constraints.insets = new Insets(5, 5, 0, 5);

constraints.weightx = 1.0D;

layout.setConstraints(typeComboBox, constraints);

settingsPanel.add(typeComboBox);

JLabel serverLabel = new JLabel("Server:");

constraints = new GridBagConstraints();

constraints.anchor = GridBagConstraints.EAST;

constraints.insets = new Insets(5, 5, 0, 0);

layout.setConstraints(serverLabel, constraints);

settingsPanel.add(serverLabel);

serverTextField = new JTextField(25);

constraints = new GridBagConstraints();

constraints.gridwidth = GridBagConstraints.REMAINDER;

constraints.insets = new Insets(5, 5, 0, 5);

constraints.weightx = 1.0D;

layout.setConstraints(serverTextField, constraints);

settingsPanel.add(serverTextField);

JLabel usernameLabel = new JLabel("Username:");

constraints = new GridBagConstraints();

constraints.anchor = GridBagConstraints.EAST;

constraints.insets = new Insets(5, 5, 0, 0);

layout.setConstraints(usernameLabel, constraints);

settingsPanel.add(usernameLabel);

usernameTextField = new JTextField();

constraints = new GridBagConstraints();

constraints.anchor = GridBagConstraints.WEST;

constraints.fill = GridBagConstraints.HORIZONTAL;

constraints.gridwidth = GridBagConstraints.REMAINDER;

constraints.insets = new Insets(5, 5, 0, 5);

constraints.weightx = 1.0D;

layout.setConstraints(usernameTextField, constraints);

settingsPanel.add(usernameTextField);

JLabel passwordLabel = new JLabel("Password:");

constraints = new GridBagConstraints();

constraints.anchor = GridBagConstraints.EAST;

constraints.insets = new Insets(5, 5, 5, 0);

layout.setConstraints(passwordLabel, constraints);

settingsPanel.add(passwordLabel);

passwordField = new JPasswordField();

constraints = new GridBagConstraints();

constraints.anchor = GridBagConstraints.WEST;

constraints.fill = GridBagConstraints.HORIZONTAL;

constraints.gridwidth = GridBagConstraints.REMAINDER;

constraints.insets = new Insets(5, 5, 5, 5);

constraints.weightx = 1.0D;

layout.setConstraints(passwordField, constraints);

settingsPanel.add(passwordField);

JLabel smtpServerLabel = new JLabel("SMTP Server:");

constraints = new GridBagConstraints();

constraints.anchor = GridBagConstraints.EAST;

constraints.insets = new Insets(5, 5, 5, 0);

layout.setConstraints(smtpServerLabel, constraints);

settingsPanel.add(smtpServerLabel);

smtpServerTextField = new JTextField(25);

constraints = new GridBagConstraints();

constraints.gridwidth = GridBagConstraints.REMAINDER;

constraints.insets = new Insets(5, 5, 5, 5);

constraints.weightx = 1.0D;

layout.setConstraints(smtpServerTextField, constraints);

settingsPanel.add(smtpServerTextField);

// Setup buttons panel.

JPanel buttonsPanel = new JPanel();

JButton connectButton = new JButton("Connect");

connectButton.addActionListener(new ActionListener() {

public void actionPerformed(ActionEvent e) {

actionConnect();

}

});

buttonsPanel.add(connectButton);

JButton cancelButton = new JButton("Cancel");

cancelButton.addActionListener(new ActionListener() {

public void actionPerformed(ActionEvent e) {

actionCancel();

}

});

buttonsPanel.add(cancelButton);

// Add panels to display.

getContentPane().setLayout(new BorderLayout());

getContentPane().add(settingsPanel, BorderLayout.CENTER);

getContentPane().add(buttonsPanel, BorderLayout.SOUTH);

// Size dialog to components.

pack();

// Center dialog over application.

setLocationRelativeTo(parent);

}

// Validate connection settings and close dialog.

private void actionConnect() {

if (serverTextField.getText().trim().length() < 1

|| usernameTextField.getText().trim().length() < 1

|| passwordField.getPassword().length < 1

|| smtpServerTextField.getText().trim().length() < 1) {

JOptionPane.showMessageDialog(this,

"One or more settings is missing.",

"Missing Setting(s)", JOptionPane.ERROR_MESSAGE);

return;

}

// Close dialog.

dispose();

}

// Cancel connecting and exit program.

private void actionCancel() {

System.exit(0);

}

// Get e-mail server type.

public String getType() {

return (String) typeComboBox.getSelectedItem();

}

// Get e-mail server.

public String getServer() {

return serverTextField.getText();

}

// Get e-mail username.

public String getUsername() {

return usernameTextField.getText();

}

// Get e-mail password.

public String getPassword() {

return new String(passwordField.getPassword());

}

// Get e-mail SMTP server.

public String getSmtpServer() {

return smtpServerTextField.getText();

}

MessagesTableModel:

import java.util.*;

import javax.mail.*;

import javax.swing.*;

import javax.swing.table.*;

// This class manages the e-mail table's data.

public class MessagesTableModel extends AbstractTableModel {

// These are the names for the table's columns.

private static final String[] columnNames = {"Sender",

"Subject", "Date"};

// The table's list of messages.

private ArrayList messageList = new ArrayList();

// Sets the table's list of messages.

public void setMessages(Message[] messages) {

for (int i = messages.length - 1; i >= 0; i--) {

messageList.add(messages[i]);

}

// Fire table data change notification to table.

fireTableDataChanged();

}

// Get a message for the specified row.

public Message getMessage(int row) {

return (Message) messageList.get(row);

}

// Remove a message from the list.

public void deleteMessage(int row) {

messageList.remove(row);

// Fire table row deletion notification to table.

fireTableRowsDeleted(row, row);

}

// Get table's column count.

public int getColumnCount() {

return columnNames.length;

}

// Get a column's name.

public String getColumnName(int col) {

return columnNames[col];

}

// Get table's row count.

public int getRowCount() {

return messageList.size();

}

// Get value for a specific row and column combination.

public Object getValueAt(int row, int col) {

try {

Message message = (Message) messageList.get(row);

switch (col) {

case 0: // Sender

Address[] senders = message.getFrom();

if (senders != null || senders.length > 0) {

return senders[0].toString();

} else {

return "[none]";

}

case 1: // Subject

String subject = message.getSubject();

if (subject != null && subject.length() > 0) {

return subject;

} else {

return "[none]";

}

case 2: // Date

Date date = message.getSentDate();

if (date != null) {

return date.toString();

} else {

return "[none]";

}

} catch (Exception e) {

// Fail silently.

return "";

}

return "";

}

MessageDialog:

import java.awt.*;

import java.awt.event.*;

import javax.mail.*;

import javax.swing.*;

// This class displays the dialog used for creating messages.

public class MessageDialog extends JDialog {

// Dialog message identifiers.

public static final int NEW = 0;

public static final int REPLY = 1;

public static final int FORWARD = 2;

// Message from, to and subject text fields.

private JTextField fromTextField, toTextField;

private JTextField subjectTextField;

// Message content text area.

private JTextArea contentTextArea;

// Flag specifying whether or not dialog was cancelled.

private boolean cancelled;

// Constructor for dialog.

public MessageDialog(Frame parent, int type, Message message)

throws Exception {

// Call super constructor, specifying that dialog is modal.

super(parent, true);

/* Set dialog title and get message's "to", "subject"

and "content" values based on message type. */

String to = "", subject = "", content = "";

switch (type) {

// Reply message.

case REPLY:

setTitle("Reply To Message");

// Get message "to" value

Address[] senders = message.getFrom();

if (senders != null || senders.length > 0) {

to = senders[0].toString();

}

to = message.getFrom()[0].toString();

// Get message subject.

subject = message.getSubject();

if (subject != null && subject.length() > 0) {

subject = "RE: " + subject;

} else {

subject = "RE:";

}

// Get message content and add "REPLIED TO" notation.

content = "\n----------------- " +

"REPLIED TO MESSAGE" +

" -----------------\n" +

EmailClient.getMessageContent(message);

break;

// Forward message.

case FORWARD:

setTitle("Forward Message");

// Get message subject.

subject = message.getSubject();

if (subject != null && subject.length() > 0) {

subject = "FWD: " + subject;

} else {

subject = "FWD:";

}

// Get message content and add "FORWARDED" notation.

content = "\n----------------- " +

"FORWARDED MESSAGE" +

" -----------------\n" +

EmailClient.getMessageContent(message);

break;

// New message.

default:

setTitle("New Message");

}

// Handle closing events.

addWindowListener(new WindowAdapter() {

public void windowClosing(WindowEvent e) {

actionCancel();

}

});

// Setup fields panel.

JPanel fieldsPanel = new JPanel();

GridBagConstraints constraints;

GridBagLayout layout = new GridBagLayout();

fieldsPanel.setLayout(layout);

JLabel fromLabel = new JLabel("From:");

constraints = new GridBagConstraints();

constraints.anchor = GridBagConstraints.EAST;

constraints.insets = new Insets(5, 5, 0, 0);

layout.setConstraints(fromLabel, constraints);

fieldsPanel.add(fromLabel);

fromTextField = new JTextField();

constraints = new GridBagConstraints();

constraints.fill = GridBagConstraints.HORIZONTAL;

constraints.gridwidth = GridBagConstraints.REMAINDER;

constraints.insets = new Insets(5, 5, 0, 0);

layout.setConstraints(fromTextField, constraints);

fieldsPanel.add(fromTextField);

JLabel toLabel = new JLabel("To:");

constraints = new GridBagConstraints();

constraints.anchor = GridBagConstraints.EAST;

constraints.insets = new Insets(5, 5, 0, 0);

layout.setConstraints(toLabel, constraints);

fieldsPanel.add(toLabel);

toTextField = new JTextField(to);

constraints = new GridBagConstraints();

constraints.fill = GridBagConstraints.HORIZONTAL;

constraints.gridwidth = GridBagConstraints.REMAINDER;

constraints.insets = new Insets(5, 5, 0, 0);

constraints.weightx = 1.0D;

layout.setConstraints(toTextField, constraints);

fieldsPanel.add(toTextField);

JLabel subjectLabel = new JLabel("Subject:");

constraints = new GridBagConstraints();

constraints.insets = new Insets(5, 5, 5, 0);

layout.setConstraints(subjectLabel, constraints);

fieldsPanel.add(subjectLabel);

subjectTextField = new JTextField(subject);

constraints = new GridBagConstraints();

constraints.fill = GridBagConstraints.HORIZONTAL;

constraints.gridwidth = GridBagConstraints.REMAINDER;

constraints.insets = new Insets(5, 5, 5, 0);

layout.setConstraints(subjectTextField, constraints);

fieldsPanel.add(subjectTextField);

// Setup content panel.

JScrollPane contentPanel = new JScrollPane();

contentTextArea = new JTextArea(content, 10, 50);

contentPanel.setViewportView(contentTextArea);

// Setup buttons panel.

JPanel buttonsPanel = new JPanel();

JButton sendButton = new JButton("Send");

sendButton.addActionListener(new ActionListener() {

public void actionPerformed(ActionEvent e) {

actionSend();

}

});

buttonsPanel.add(sendButton);

JButton cancelButton = new JButton("Cancel");

cancelButton.addActionListener(new ActionListener() {

public void actionPerformed(ActionEvent e) {

actionCancel();

}

});

buttonsPanel.add(cancelButton);

// Add panels to display.

getContentPane().setLayout(new BorderLayout());

getContentPane().add(fieldsPanel, BorderLayout.NORTH);

getContentPane().add(contentPanel, BorderLayout.CENTER);

getContentPane().add(buttonsPanel, BorderLayout.SOUTH);

// Size dialog to components.

pack();

// Center dialog over application.

setLocationRelativeTo(parent);

}

// Validate message fields and close dialog.

private void actionSend() {

if (fromTextField.getText().trim().length() < 1

|| toTextField.getText().trim().length() < 1

|| subjectTextField.getText().trim().length() < 1

|| contentTextArea.getText().trim().length() < 1) {

JOptionPane.showMessageDialog(this,

"One or more fields is missing.",

"Missing Field(s)", JOptionPane.ERROR_MESSAGE);

return;

}

// Close dialog.

dispose();

}

// Cancel creating this message and close dialog.

private void actionCancel() {

cancelled = true;

// Close dialog.

dispose();

}

// Show dialog.

public boolean display() {

show();

// Return whether or not display was successful.

return !cancelled;

}

// Get message's "From" field value.

public String getFrom() {

return fromTextField.getText();

}

// Get message's "To" field value.

public String getTo() {

return toTextField.getText();

}

// Get message's "Subject" field value.

public String getSubject() {

return subjectTextField.getText();

}

// Get message's "content" field value.

public String getContent() {

return contentTextArea.getText();

}

DownloadingDialog:

import java.awt.*;

import javax.swing.*;

/* This class displays a simple dialog instructing the user

that messages are being downloaded. */

public class DownloadingDialog extends JDialog {

// Constructor for dialog.

public DownloadingDialog(Frame parent) {

// Call super constructor, specifying that dialog is modal.

super(parent, true);

// Set dialog title.

setTitle("E-mail Client");

// Instruct window not to close when the "X" is clicked.

setDefaultCloseOperation(DO_NOTHING_ON_CLOSE);

// Put a message with a nice border in this dialog.

JPanel contentPane = new JPanel();

contentPane.setBorder(

BorderFactory.createEmptyBorder(5, 5, 5, 5));

contentPane.add(new JLabel("Downloading messages..."));

setContentPane(contentPane);

// Size dialog to components.

pack();

// Center dialog over application.

setLocationRelativeTo(parent);

}

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