Webseiten herunterladen und speichern

Folgender, sehr einfacher, 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 /**
 10  * GrapHtmlDemo zeigt, wie man mit Java Quelltext von Webseiten herunterladen und speichern kann.
 11  *
 12  * @author Gernot Segieth
 13  */
 14 public class GrapHtmlDemo {
 15    private final JFrame frame;
 16    private JTextField targetField;
 17    private JTextArea tArea;
 18    private JTabbedPane tabbedPane;
 19    private JFileChooser chooser;
 20 
 21    public GrapHtmlDemo(String title) {
 22       JPanel panel = new JPanel(new BorderLayout(0, 5));
 23       panel.setBorder(BorderFactory.createEmptyBorder(10, 5, 10, 5));
 24       targetField = new JTextField();
 25       targetField.addActionListener(new TargetFieldAction());
 26       tabbedPane = new JTabbedPane();
 27       tabbedPane.setTabPlacement(JTabbedPane.BOTTOM);
 28       tArea = new JTextArea();
 29       tabbedPane.addTab("HTML-Code", new JScrollPane(tArea));
 30 
 31       panel.add(createNorthPanel(), BorderLayout.NORTH);
 32       panel.add(tabbedPane, BorderLayout.CENTER);
 33       panel.add(createSouthPanel(), BorderLayout.SOUTH);
 34 
 35       chooser = new JFileChooser();
 36       FileNameExtensionFilter filter = new FileNameExtensionFilter(
 37         "Plain Text", "txt", "html", "css", "js", "php", "java", "xml");
 38       chooser.setFileFilter(filter);
 39       
 40       frame = new JFrame(title);
 41       Dimension dim = Toolkit.getDefaultToolkit().getScreenSize();
 42       frame.setSize(dim.width * 66 / 100, dim.height * 66 / 100);
 43       frame.setLocationRelativeTo(null);
 44       frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
 45       frame.add(panel);
 46       frame.setVisible(true);
 47    }
 48 
 49    private JPanel createNorthPanel() {
 50       JPanel panel = new JPanel(new BorderLayout(5, 0));
 51       panel.add(new JLabel("URL:"), BorderLayout.WEST);
 52       panel.add(targetField, BorderLayout.CENTER);
 53       panel.add(new JButton(new TargetFieldAction("Los!")), BorderLayout.EAST);
 54       return panel;
 55    }
 56 
 57    private JPanel createSouthPanel() {
 58       JPanel panel = new JPanel(new FlowLayout(FlowLayout.RIGHT));
 59       panel.add(new JButton(new StoreAction("Speichern")), BorderLayout.EAST);
 60       return panel;
 61    }
 62 
 63    private void getContent() {
 64       if(tabbedPane.getTabCount() > 1) {
 65          tabbedPane.remove(1);
 66       }
 67       String urlString = targetField.getText().trim();
 68       if(!urlString.startsWith("http")) {
 69          urlString = "https://" + urlString;
 70          targetField.setText(urlString);
 71       }
 72       try {
 73          tArea.setText(null);
 74          readContent(new URL(urlString));
 75       }
 76       catch(Exception ex) {
 77          JTextArea eArea = new JTextArea(ex.toString());
 78          eArea.setBackground(Color.PINK);
 79          tabbedPane.addTab("Error", new JScrollPane(eArea));
 80          tabbedPane.setSelectedIndex(1);
 81       }
 82    } 
 83 
 84    private void readContent(URL url) throws Exception {
 85       Scanner scan = new Scanner(url.openStream());
 86       if (scan != null) {
 87          while(scan.hasNextLine()) {
 88             tArea.append(scan.nextLine());
 89             tArea.append("\n");
 90          }
 91       }
 92    }
 93 
 94    private void storeContent() {
 95       String text = tArea.getText();
 96       if(!text.isEmpty()) {
 97          int result = chooser.showSaveDialog(frame);
 98          if(result == JFileChooser.APPROVE_OPTION) {
 99             File file = chooser.getSelectedFile();
100             try {
101                BufferedWriter writer = new BufferedWriter(new FileWriter(file));         
102                writer.write(text);
103                writer.flush();
104                writer.close();
105             } catch(IOException e) {
106                System.err.println(e);
107                JOptionPane.showMessageDialog(frame, e.getClass().getName(),
108                   "ERROR: Fehler beim Schreiben der Datei auf den Datenträger!",
109                   JOptionPane.ERROR_MESSAGE);
110             }
111          }
112       }
113    }
114 
115    public static void main(String[] args) {
116       try {
117          UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
118       }
119       catch(Exception e) {
120          System.err.println(e);
121       }
122 
123       SwingUtilities.invokeLater(new Runnable() {
124          @Override
125          public void run() {
126             new GrapHtmlDemo("HTML-Code von Webseiten");
127          }
128       });
129    }
130 
131    class TargetFieldAction extends AbstractAction {
132       TargetFieldAction() {
133          this(null);
134       }
135       
136       TargetFieldAction(String text) {
137          super(text);
138       }
139       
140       @Override
141       public void actionPerformed(ActionEvent e) {
142          getContent();
143       }
144    }
145 
146    class StoreAction extends AbstractAction {
147       StoreAction(String text) {
148          super(text);
149       }
150       
151       @Override
152       public void actionPerformed(ActionEvent e) {
153          storeContent();
154       }
155    }
156 
157 }