File Download Manager
import java.awt.BorderLayout;
import java.awt.Component;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.KeyEvent;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import java.io.InputStream;
import java.io.RandomAccessFile;
import java.net.HttpURLConnection;
import java.net.URL;
import java.util.ArrayList;
import java.util.Observable;
import java.util.Observer;
import javax.swing.BorderFactory;
import javax.swing.JButton;
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.JProgressBar;
import javax.swing.JScrollPane;
import javax.swing.JTable;
import javax.swing.JTextField;
import javax.swing.ListSelectionModel;
import javax.swing.event.ListSelectionEvent;
import javax.swing.event.ListSelectionListener;
import javax.swing.table.AbstractTableModel;
import javax.swing.table.TableCellRenderer;
public class DownloadManager extends JFrame implements Observer {
private JTextField addTextField = new JTextField(30);
private DownloadsTableModel tableModel = new DownloadsTableModel();
private JTable table;
private JButton pauseButton = new JButton("Pause");
private JButton resumeButton = new JButton("Resume");
private JButton cancelButton, clearButton;
private Download selectedDownload;
private boolean clearing;
public DownloadManager() {
setTitle("Download Manager");
setSize(640, 480);
addWindowListener(new WindowAdapter() {
public void windowClosing(WindowEvent e) {
System.exit(0);
}
});
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) {
System.exit(0);
}
});
fileMenu.add(fileExitMenuItem);
menuBar.add(fileMenu);
setJMenuBar(menuBar);
// Set up add panel.
JPanel addPanel = new JPanel();
addPanel.add(addTextField);
JButton addButton = new JButton("Add Download");
addButton.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
actionAdd();
}
});
addPanel.add(addButton);
// Set up Downloads table.
table = new JTable(tableModel);
table.getSelectionModel().addListSelectionListener(new ListSelectionListener() {
public void valueChanged(ListSelectionEvent e) {
tableSelectionChanged();
}
});
table.setSelectionMode(ListSelectionModel.SINGLE_SELECTION);
ProgressRenderer renderer = new ProgressRenderer(0, 100);
renderer.setStringPainted(true); // show progress text
table.setDefaultRenderer(JProgressBar.class, renderer);
table.setRowHeight((int) renderer.getPreferredSize().getHeight());
JPanel downloadsPanel = new JPanel();
downloadsPanel.setBorder(BorderFactory.createTitledBorder("Downloads"));
downloadsPanel.setLayout(new BorderLayout());
downloadsPanel.add(new JScrollPane(table), BorderLayout.CENTER);
JPanel buttonsPanel = new JPanel();
pauseButton.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
actionPause();
}
});
pauseButton.setEnabled(false);
buttonsPanel.add(pauseButton);
resumeButton.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
actionResume();
}
});
resumeButton.setEnabled(false);
buttonsPanel.add(resumeButton);
cancelButton = new JButton("Cancel");
cancelButton.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
actionCancel();
}
});
cancelButton.setEnabled(false);
buttonsPanel.add(cancelButton);
clearButton = new JButton("Clear");
clearButton.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
actionClear();
}
});
clearButton.setEnabled(false);
buttonsPanel.add(clearButton);
getContentPane().setLayout(new BorderLayout());
getContentPane().add(addPanel, BorderLayout.NORTH);
getContentPane().add(downloadsPanel, BorderLayout.CENTER);
getContentPane().add(buttonsPanel, BorderLayout.SOUTH);
}
private void actionAdd() {
URL verifiedUrl = verifyUrl(addTextField.getText());
if (verifiedUrl != null) {
tableModel.addDownload(new Download(verifiedUrl));
addTextField.setText(""); // reset add text field
} else {
JOptionPane.showMessageDialog(this, "Invalid Download URL", "Error",
JOptionPane.ERROR_MESSAGE);
}
}
private URL verifyUrl(String url) {
if (!url.toLowerCase().startsWith("http://"))
return null;
URL verifiedUrl = null;
try {
verifiedUrl = new URL(url);
} catch (Exception e) {
return null;
}
if (verifiedUrl.getFile().length() < 2)
return null;
return verifiedUrl;
}
private void tableSelectionChanged() {
if (selectedDownload != null)
selectedDownload.deleteObserver(DownloadManager.this);
if (!clearing && table.getSelectedRow() > -1) {
selectedDownload = tableModel.getDownload(table.getSelectedRow());
selectedDownload.addObserver(DownloadManager.this);
updateButtons();
}
}
private void actionPause() {
selectedDownload.pause();
updateButtons();
}
private void actionResume() {
selectedDownload.resume();
updateButtons();
}
private void actionCancel() {
selectedDownload.cancel();
updateButtons();
}
private void actionClear() {
clearing = true;
tableModel.clearDownload(table.getSelectedRow());
clearing = false;
selectedDownload = null;
updateButtons();
}
private void updateButtons() {
if (selectedDownload != null) {
int status = selectedDownload.getStatus();
switch (status) {
case Download.DOWNLOADING:
pauseButton.setEnabled(true);
resumeButton.setEnabled(false);
cancelButton.setEnabled(true);
clearButton.setEnabled(false);
break;
case Download.PAUSED:
pauseButton.setEnabled(false);
resumeButton.setEnabled(true);
cancelButton.setEnabled(true);
clearButton.setEnabled(false);
break;
case Download.ERROR:
pauseButton.setEnabled(false);
resumeButton.setEnabled(true);
cancelButton.setEnabled(false);
clearButton.setEnabled(true);
break;
default: // COMPLETE or CANCELLED
pauseButton.setEnabled(false);
resumeButton.setEnabled(false);
cancelButton.setEnabled(false);
clearButton.setEnabled(true);
}
} else {
pauseButton.setEnabled(false);
resumeButton.setEnabled(false);
cancelButton.setEnabled(false);
clearButton.setEnabled(false);
}
}
public void update(Observable o, Object arg) {
// Update buttons if the selected download has changed.
if (selectedDownload != null && selectedDownload.equals(o))
updateButtons();
}
// Run the Download Manager.
public static void main(String[] args) {
DownloadManager manager = new DownloadManager();
manager.setVisible(true);
}
}
class Download extends Observable implements Runnable {
private static final int MAX_BUFFER_SIZE = 1024;
public static final String STATUSES[] = { "Downloading", "Paused", "Complete", "Cancelled",
"Error" };
public static final int DOWNLOADING = 0;
public static final int PAUSED = 1;
public static final int COMPLETE = 2;
public static final int CANCELLED = 3;
public static final int ERROR = 4;
private URL url; // download URL
private int size; // size of download in bytes
private int downloaded; // number of bytes downloaded
private int status; // current status of download
// Constructor for Download.
public Download(URL url) {
this.url = url;
size = -1;
downloaded = 0;
status = DOWNLOADING;
// Begin the download.
download();
}
// Get this download's URL.
public String getUrl() {
return url.toString();
}
// Get this download's size.
public int getSize() {
return size;
}
// Get this download's progress.
public float getProgress() {
return ((float) downloaded / size) * 100;
}
public int getStatus() {
return status;
}
public void pause() {
status = PAUSED;
stateChanged();
}
public void resume() {
status = DOWNLOADING;
stateChanged();
download();
}
public void cancel() {
status = CANCELLED;
stateChanged();
}
private void error() {
status = ERROR;
stateChanged();
}
private void download() {
Thread thread = new Thread(this);
thread.start();
}
// Get file name portion of URL.
private String getFileName(URL url) {
String fileName = url.getFile();
return fileName.substring(fileName.lastIndexOf('/') + 1);
}
// Download file.
public void run() {
RandomAccessFile file = null;
InputStream stream = null;
try {
// Open connection to URL.
HttpURLConnection connection = (HttpURLConnection) url.openConnection();
// Specify what portion of file to download.
connection.setRequestProperty("Range", "bytes=" + downloaded + "-");
// Connect to server.
connection.connect();
// Make sure response code is in the 200 range.
if (connection.getResponseCode() / 100 != 2) {
error();
}
// Check for valid content length.
int contentLength = connection.getContentLength();
if (contentLength < 1) {
error();
}
/*
* Set the size for this download if it hasn't been already set.
*/
if (size == -1) {
size = contentLength;
stateChanged();
}
// Open file and seek to the end of it.
file = new RandomAccessFile(getFileName(url), "rw");
file.seek(downloaded);
stream = connection.getInputStream();
while (status == DOWNLOADING) {
/*
* Size buffer according to how much of the file is left to download.
*/
byte buffer[];
if (size - downloaded > MAX_BUFFER_SIZE) {
buffer = new byte[MAX_BUFFER_SIZE];
} else {
buffer = new byte[size - downloaded];
}
// Read from server into buffer.
int read = stream.read(buffer);
if (read == -1)
break;
// Write buffer to file.
file.write(buffer, 0, read);
downloaded += read;
stateChanged();
}
/*
* Change status to complete if this point was reached because downloading
* has finished.
*/
if (status == DOWNLOADING) {
status = COMPLETE;
stateChanged();
}
} catch (Exception e) {
error();
} finally {
// Close file.
if (file != null) {
try {
file.close();
} catch (Exception e) {
}
}
// Close connection to server.
if (stream != null) {
try {
stream.close();
} catch (Exception e) {
}
}
}
}
private void stateChanged() {
setChanged();
notifyObservers();
}
}
class DownloadsTableModel extends AbstractTableModel implements Observer {
private static final String[] columnNames = { "URL", "Size", "Progress", "Status" };
private static final Class[] columnClasses = { String.class, String.class, JProgressBar.class,
String.class };
private ArrayList<Download> downloadList = new ArrayList<Download>();
public void addDownload(Download download) {
download.addObserver(this);
downloadList.add(download);
fireTableRowsInserted(getRowCount() - 1, getRowCount() - 1);
}
public Download getDownload(int row) {
return (Download) downloadList.get(row);
}
public void clearDownload(int row) {
downloadList.remove(row);
fireTableRowsDeleted(row, row);
}
public int getColumnCount() {
return columnNames.length;
}
public String getColumnName(int col) {
return columnNames[col];
}
public Class getColumnClass(int col) {
return columnClasses[col];
}
public int getRowCount() {
return downloadList.size();
}
public Object getValueAt(int row, int col) {
Download download = downloadList.get(row);
switch (col) {
case 0: // URL
return download.getUrl();
case 1: // Size
int size = download.getSize();
return (size == -1) ? "" : Integer.toString(size);
case 2: // Progress
return new Float(download.getProgress());
case 3: // Status
return Download.STATUSES[download.getStatus()];
}
return "";
}
public void update(Observable o, Object arg) {
int index = downloadList.indexOf(o);
fireTableRowsUpdated(index, index);
}
}
class ProgressRenderer extends JProgressBar implements TableCellRenderer {
public ProgressRenderer(int min, int max) {
super(min, max);
}
public Component getTableCellRendererComponent(JTable table, Object value, boolean isSelected,
boolean hasFocus, int row, int column) {
setValue((int) ((Float) value).floatValue());
return this;
}
}
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