/* * A download manager application with a simple Java GUI */ // Import the Swing GUI components and a few other classes importPackage(javax.swing); importClass(javax.swing.border.EmptyBorder); importClass(java.awt.event.ActionListener); importClass(java.net.URL); importClass(java.io.FileOutputStream); importClass(java.lang.Thread); // Create some GUI widgets var frame = new JFrame("Rhino URL Fetcher"); // The application window var urlfield = new JTextField(30); // URL entry field var button = new JButton("Download"); // Button to start download var filechooser = new JFileChooser(); // A file selection dialog var row = Box.createHorizontalBox(); // A box for field and button var col = Box.createVerticalBox(); // For the row & progress bars var padding = new EmptyBorder(3,3,3,3); // Padding for rows // Put them all together and display the GUI row.add(urlfield); // Input field goes in the row row.add(button); // Button goes in the row col.add(row); // Row goes in the column frame.add(col); // Column goes in the frame row.setBorder(padding); // Add some padding to the row frame.pack(); // Set to minimum size frame.visible = true; // Make the window visible // When anything happens to the window, call this function. frame.addWindowListener(function(e, name) { // If the user closes the window, exit the application. if (name === "windowClosing") // Rhino adds the name argument java.lang.System.exit(0); }); // When the user clicks the button, call this function button.addActionListener(function() { try { // Create a java.net.URL to represent the source URL. // (This will check that the user's input is well-formed) var url = new URL(urlfield.text); // Ask the user to select a file to save the URL contents to. var response = filechooser.showSaveDialog(frame); // Quit now if they clicked Cancel if (response != JFileChooser.APPROVE_OPTION) return; // Otherwise, get the java.io.File that represents the destination file var file = filechooser.getSelectedFile(); // Now start a new thread to download the url new java.lang.Thread(function() { download(url,file); }).start(); } catch(e) { // Display a dialog box if anything goes wrong JOptionPane.showMessageDialog(frame, e.message, "Exception", JOptionPane.ERROR_MESSAGE); } }); // Use java.net.URL, etc. to download the content of the URL and use // java.io.File, etc. to save that content to a file. Display download // progress in a JProgressBar component. This will be invoked in a new thread. function download(url, file) { try { // Each time we download a URL we add a new row to the window // to display the url, the filename, and the download progress var row = Box.createHorizontalBox(); // Create the row row.setBorder(padding); // Give it some padding var label = url.toString() + ": "; // Display the URL row.add(new JLabel(label)); // in a JLabel var bar = new JProgressBar(0, 100); // Add a progress bar bar.stringPainted = true; // Display filename in bar.string = file.toString(); // the progress bar row.add(bar); // Add bar to this new row col.add(row); // Add row to the column frame.pack(); // Resize window // We don't yet know the URL size, so bar starts just animating bar.indeterminate = true; // Now connect to the server and get the URL length if we can var conn = url.openConnection(); // Get java.net.URLConnection conn.connect(); // Connect and wait for headers var len = conn.contentLength; // See if we have URL length if (len) { // If length known, then bar.maximum = len; // set the bar to display bar.indeterminate = false; // the percent downloaded } // Get input and output streams var input = conn.inputStream; // To read bytes from server var output = new FileOutputStream(file); // To write bytes to file // Create an array of 4k bytes as an input buffer var buffer = java.lang.reflect.Array.newInstance(java.lang.Byte.TYPE, 4096); var num; while((num=input.read(buffer)) != -1) { // Read and loop until EOF output.write(buffer, 0, num); // Write bytes to file bar.value += num; // Update progress bar } output.close(); // Close streams when done input.close(); } catch(e) { // If anything goes wrong, display error in progress bar if (bar) { bar.indeterminate = false; // Stop animating bar.string = e.toString(); // Replace filename with error } } }
Example 12-1. A download manager application with Rhino

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