Webseiten herunterladen und speichern

Folgender vollständiger Code zeigt, wie man Webseiten mit Java downloaden und auf der Festplatte speichern kann:

  1 import java.io.*;
  2 import java.awt.*;
  3 import java.awt.event.*;
  4 import java.net.*;
  5 import java.util.*;
  6 import javax.swing.*;
  7 import javax.swing.filechooser.*;
  8 
  9 public class GrapHtmlDemo {
 10    private final JFrame frame;
 11    private JTextField targetField;
 12    private JTextArea tArea;
 13    private JTabbedPane tabbedPane;
 14    private JFileChooser chooser;
 15 
 16    public GrapHtmlDemo(String title) {
 17       JPanel panel = new JPanel(new BorderLayout(0, 5));
 18       panel.setBorder(BorderFactory.createEmptyBorder(10, 5, 10, 5));
 19       targetField = new JTextField();
 20       targetField.addActionListener(new TargetFieldAction());
 21       tabbedPane = new JTabbedPane();
 22       tabbedPane.setTabPlacement(JTabbedPane.BOTTOM);
 23       tArea = new JTextArea();
 24       tabbedPane.addTab("HTML-Code", new JScrollPane(tArea));
 25 
 26       panel.add(createNorthPanel(), BorderLayout.NORTH);
 27       panel.add(tabbedPane, BorderLayout.CENTER);
 28       panel.add(createSouthPanel(), BorderLayout.SOUTH);
 29 
 30       chooser = new JFileChooser();
 31       FileNameExtensionFilter filter = new FileNameExtensionFilter(
 32         "Plain Text", "txt", "html", "css", "js");
 33       chooser.setFileFilter(filter);
 34       
 35       frame = new JFrame(title);
 36       Dimension dim = Toolkit.getDefaultToolkit().getScreenSize();
 37       frame.setSize(dim.width * 66 / 100, dim.height * 66 / 100);
 38       frame.setLocationRelativeTo(null);
 39       frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
 40       frame.add(panel);
 41       frame.setVisible(true);
 42    }
 43 
 44    private JPanel createNorthPanel() {
 45       JPanel panel = new JPanel(new BorderLayout(5, 0));
 46       panel.add(new JLabel("URL:"), BorderLayout.WEST);
 47       panel.add(targetField, BorderLayout.CENTER);
 48       panel.add(new JButton(new TargetFieldAction("Los!")), BorderLayout.EAST);
 49       return panel;
 50    }
 51 
 52    private JPanel createSouthPanel() {
 53       JPanel panel = new JPanel(new FlowLayout(FlowLayout.RIGHT));
 54       panel.add(new JButton(new StoreAction("Speichern")), BorderLayout.EAST);
 55       return panel;
 56    }
 57 
 58    private void readContent(URL url) throws Exception {
 59       Scanner scan = new Scanner(url.openStream());
 60       if (scan != null) {
 61          while(scan.hasNextLine()) {
 62             tArea.append(scan.nextLine()+"\n\r");
 63          }
 64       }
 65    }
 66 
 67    private void storeContent() {
 68       int result = chooser.showSaveDialog(frame);
 69       if(result == JFileChooser.APPROVE_OPTION) {
 70          File file = chooser.getSelectedFile();
 71          try {
 72             BufferedWriter writer = new BufferedWriter(new FileWriter(file));         
 73             writer.write(tArea.getText());
 74             writer.flush();
 75             writer.close();
 76          } catch(IOException e) {
 77             System.err.println(e);
 78             JOptionPane.showMessageDialog(frame, e.getClass().getName(),
 79                "ERROR: Fehler beim Schreiben der Datei auf den Datenträger!",
 80                JOptionPane.ERROR_MESSAGE);
 81          }
 82       }
 83    }
 84 
 85    public static void main(String[] args) {
 86       try {
 87          UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
 88       }
 89       catch(Exception e) {
 90          System.err.println(e);
 91       }
 92 
 93       SwingUtilities.invokeLater(new Runnable() {
 94          @Override
 95          public void run() {
 96             new GrapHtmlDemo("HTML-Code von Webseiten");
 97          }
 98       });
 99    }
100 
101    class TargetFieldAction extends AbstractAction {
102       TargetFieldAction() {
103          this(null);
104       }
105       
106       TargetFieldAction(String text) {
107          super(text);
108       }
109       
110       @Override
111       public void actionPerformed(ActionEvent e) {
112          if(tabbedPane.getTabCount() > 1) {
113             tabbedPane.remove(1);
114          }
115          String urlString = targetField.getText().trim();
116          if(!urlString.startsWith("http")) {
117             urlString = "https://" + urlString;
118             targetField.setText(urlString);
119          }
120          try {
121             tArea.setText(null);
122             readContent(new URL(urlString));
123          }
124          catch(Exception ex) {
125             JTextArea eArea = new JTextArea(ex.toString());
126             eArea.setBackground(Color.PINK);
127             tabbedPane.addTab("Error", new JScrollPane(eArea));
128             tabbedPane.setSelectedIndex(1);
129          }
130       }
131    }
132 
133    class StoreAction extends AbstractAction {
134       StoreAction(String text) {
135          super(text);
136       }
137       
138       @Override
139       public void actionPerformed(ActionEvent e) {
140          storeContent();
141       }
142    }
143 
144 }