JWebBrower源码

package org.jscience.net;

import org.jscience.util.Settings;
import org.jscience.util.gui.CloseButton;
import org.jscience.util.gui.ImageViewer;
import org.jscience.util.gui.JMainFrame;
import org.jscience.util.gui.Menus;

import javax.swing.*;
import javax.swing.event.HyperlinkEvent;
import javax.swing.event.HyperlinkListener;
import java.awt.*;
import java.awt.event.*;
import java.io.File;
import java.io.IOException;
import java.net.MalformedURLException;
import java.net.URL;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.Stack;

/**
 * A very plain Web Browser with minimal functionality; but still cool.
 * <p/>
 * Unfortunately, the caching doesn't work for the main display, yet. <p>
 * Check out the multiple right-mouse-click options. :-) <p>
 * At this point, the implementation is completely transient, i.e.
 * nothing is written to disk other than what you explicitly save;
 * so your homepage settings, cache and favorites are reset when you
 * restart the browser. <p>
 * No support for cookies (that may be the good news ;-), JavaScript,
 * forms, etc. at this point. <p>
 * There are several other limitations as this implementation is just based
 * on the javax.swing.JEditorPane at this point.
 * However, there are also some features that your average browser does NOT have,
 * such as the display of the server information in the view menu.
 * <p/>
 * To use a customized HTTP Agent when connecting to a web-server, you need to
 * set the system property <dfn>http.agent</dfn> accordingly before using this
 * class.
 *
 * @author Holger Antelmann
 * @see JSpider
 * @see javax.swing.JEditorPane
 */
public class JWebBrowser extends JMainFrame {
  static final long serialVersionUID = 8894203216788969688L;

  URL home;
  URLCache current;
  HashMap<URL, URLCache> cache;
  Stack<URLCache> history;
  Stack<URLCache> forwards;
  Stack<URL> favorites;
  JMenu favMenu;
  JButton stopButton;
  URLCache nowLoading;
  JURLCachePane textPane;
  JTextField textUrlField;
  JFileChooser fchooser;
  URL hyperlinkHoover;
  volatile boolean busy;
  /**
   * needed for the @#$*@#$ JEditorPane to reload the page in refresh()
   */
  static URLCache blankPage = new URLCache(Settings.getResource("org/jscience/blank_page.htm"));
  String[] favoriteDefaults = new String[]{
    Settings.getProperty("application.vendor.url"),
    Settings.getProperty("application.documentation.url"),
    "http://www.gnu.org/",
    "http://java.sun.com/",
    "http://localhost/"
  };

  /**
   * initializes with a blank page
   */
  public JWebBrowser() {
    this(blankPage);
  }

  public JWebBrowser(String urlHomeSpec) throws IOException {
    this(new URL(urlHomeSpec));
  }

  public JWebBrowser(URL homeURL) {
    this(new URLCache(homeURL));
  }

  public JWebBrowser(URLCache homeURLCache) {
    super("Holger's Java Browser", false, true);
    home = homeURLCache.getURL();
    textUrlField = new JTextField(home.toString());
    fchooser = new JFileChooser();
    history = new Stack<URLCache>();
    forwards = new Stack<URLCache>();
    favorites = new Stack<URL>();
    cache = new HashMap<URL, URLCache>();
    textPane = new JURLCachePane(cache);
    textPane.setContentType("text/html");
    textPane.setEditable(false);
    textPane.addHyperlinkListener(new HyperlinkListener() {
      public void hyperlinkUpdate(HyperlinkEvent e) {
        if (e.getEventType() == HyperlinkEvent.EventType.ACTIVATED) {
          if (!busy) setPage(e.getURL());
        } else if (e.getEventType() == HyperlinkEvent.EventType.ENTERED) {
          hyperlinkHoover = e.getURL();
          if (!busy) updateStatusText(e.getURL().toString());
        } else if (e.getEventType() == HyperlinkEvent.EventType.EXITED) {
          hyperlinkHoover = null;
          if (!busy) updateStatusText(" ");
        }
      }
    });
    textPane.addMouseListener(new MouseAdapter() {
      public void mousePressed(MouseEvent e) {
        popup(e);
      }

      public void mouseReleased(MouseEvent e) {
        popup(e);
      }

      void popup(MouseEvent e) {
        if (e.isPopupTrigger()) {
          JPopupMenu menu = getPopupMenu();
          if (hyperlinkHoover != null) {
            JMenuItem item = new JMenuItem("open in new window");
            item.addActionListener(new ActionListener() {
              public void actionPerformed(ActionEvent e) {
                URL url = hyperlinkHoover;
                if (url == null) return;
                JWebBrowser jwb = new JWebBrowser(url);
                jwb.setDefaultCloseOperation(DISPOSE_ON_CLOSE);
                jwb.setVisible(true);
              }
            });
            menu.insert(item, 0);
            item = new JMenuItem("save link");
            item.addActionListener(new ActionListener() {
              public void actionPerformed(ActionEvent e) {
                download(hyperlinkHoover);
              }
            });
            menu.insert(item, 0);
          }
          menu.show(e.getComponent(), e.getX(), e.getY());
        }
      }
    });
    JScrollPane scrollPane = new JScrollPane(textPane);
    Dimension screen = Toolkit.getDefaultToolkit().getScreenSize();
    screen.setSize((int) screen.getWidth() / 2, (int) screen.getHeight() / 2);
    scrollPane.setPreferredSize(screen);
    getContentPane().add(scrollPane, BorderLayout.CENTER);
    getContentPane().add(getToolBar(), BorderLayout.NORTH);
    setJMenuBar(getMenu());
    current = homeURLCache;
    cache.put(current.getURL(), current);
    setPage(current.getURL());
    pack();
  }

  JMenuBar getMenu() {
    JMenuBar menuBar = new JMenuBar();
    JMenuItem item;
    JMenu fileMenu = new JMenu("File");
    fileMenu.setMnemonic(KeyEvent.VK_F);
    menuBar.add(fileMenu);
    {
      item = new JMenuItem("Save page as ..");
      item.setMnemonic(KeyEvent.VK_S);
      item.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent e) {
          download(current);
        }
      });
      fileMenu.add(item);

      item = new JMenuItem("Close");
      item.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent e) {
          dispose();
        }
      });
      item.setMnemonic(KeyEvent.VK_C);
      fileMenu.add(item);

      item = new JMenuItem("Exit");
      item.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent e) {
          System.exit(0);
        }
      });
      item.setMnemonic(KeyEvent.VK_X);
      fileMenu.add(item);
    }
    JMenu viewMenu = new JMenu("View");
    viewMenu.setMnemonic(KeyEvent.VK_V);
    menuBar.add(viewMenu);
    {
      item = new JMenuItem("show header info");
      item.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent e) {
          final JDialog dialog = new JDialog(JWebBrowser.this, "header info", true);
          dialog.getContentPane().setLayout(new BorderLayout());
          String s = "cannot access header";
          try {
            s = new Spider(current.getURL()).fullHeaderAsString();
          } catch (IOException ex) {
          }
          JTextArea pane = new JTextArea(s);
          pane.setEditable(false);
          dialog.getContentPane().add(pane, BorderLayout.CENTER);
          dialog.getContentPane().add(new CloseButton(dialog), BorderLayout.SOUTH);
          dialog.pack();
          dialog.setLocationRelativeTo(JWebBrowser.this);
          dialog.setVisible(true);
        }
      });
      viewMenu.add(item);
      item = new JMenuItem("show Whois registration info");
      item.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent e) {
          final JDialog dialog = new JDialog(JWebBrowser.this, "Whois registration info", true);
          dialog.getContentPane().setLayout(new BorderLayout());
          String s = null;
          try {
            s = new Spider(current.getURL()).whois();
          } catch (IOException ex) {
          }
          if (s == null) s = "cannot access Whois registration info";
          JTextArea pane = new JTextArea(s);
          pane.setEditable(false);
          dialog.getContentPane().add(new JScrollPane(pane), BorderLayout.CENTER);
          dialog.getContentPane().add(new CloseButton(dialog), BorderLayout.SOUTH);
          dialog.pack();
          dialog.setLocationRelativeTo(JWebBrowser.this);
          dialog.setVisible(true);
        }
      });
      viewMenu.add(item);
      MenuElement[] elements = getPopupMenu().getSubElements();
      for (int i = 0; i < elements.length; i++) {
        viewMenu.add((Component) elements[i]);
      }
    }
    favMenu = new JMenu("Favorites");
    favMenu.setMnemonic(KeyEvent.VK_A);
    menuBar.add(favMenu);
    {
      item = new JMenuItem("add to favorites");
      item.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent e) {
          final URLCache uc = current;
          favorites.add(uc.getURL());
          JMenuItem nf = new JMenuItem(uc.getURL().toString());
          nf.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent ev) {
              setPage(uc.getURL());
            }
          });
          favMenu.add(nf);
        }
      });
      item.setMnemonic(KeyEvent.VK_A);
      favMenu.add(item);
      JMenu defaults = new JMenu("defaults");
      {
        for (int i = 0; i < favoriteDefaults.length; i++) {
          item = new JMenuItem(favoriteDefaults[i]);
          final int n = i;
          item.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent ev) {
              try {
                setPage(new URL(favoriteDefaults[n]));
              } catch (IOException e) {
              }
            }
          });
          defaults.add(item);
        }
      }
      favMenu.add(defaults);
      favMenu.addSeparator();
    }
    JMenu toolsMenu = new JMenu("Tools");
    toolsMenu.setMnemonic(KeyEvent.VK_T);
    menuBar.add(toolsMenu);
    {
      item = new JMenuItem("Messenger");
      item.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent e) {
          try {
            JMessenger js = new JMessenger();
            js.setDefaultCloseOperation(DISPOSE_ON_CLOSE);
            js.setVisible(true);
          } catch (IOException ex) {
            JOptionPane.showMessageDialog(JWebBrowser.this,
                    ex.getMessage(), "Messenger failed to start",
                    JOptionPane.ERROR_MESSAGE);
          }
        }
      });
      item.setMnemonic(KeyEvent.VK_U);
      toolsMenu.add(item);

      item = new JMenuItem("Chat client");
      item.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent e) {
          JChat js = new JChat();
          js.setDefaultCloseOperation(DISPOSE_ON_CLOSE);
          js.setVisible(true);
        }
      });
      item.setMnemonic(KeyEvent.VK_U);
      toolsMenu.add(item);

      item = new JMenuItem("URL tree");
      item.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent e) {
          JSpider js = new JSpider(current.getURL());
          js.setDefaultCloseOperation(DISPOSE_ON_CLOSE);
          js.setVisible(true);
        }
      });
      item.setMnemonic(KeyEvent.VK_U);
      toolsMenu.add(item);
    }
    JMenu optionMenu = new JMenu("Options");
    optionMenu.setMnemonic(KeyEvent.VK_O);
    menuBar.add(optionMenu);
    {
      item = new JMenuItem("set current page as home");
      item.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent e) {
          setHome(current.getURL());
        }
      });
      item.setMnemonic(KeyEvent.VK_S);
      optionMenu.add(item);

      item = new JMenuItem("set HTTP agent");
      item.setToolTipText("this determines how the browser identifies itself");
      item.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent e) {
          String p = JOptionPane.showInputDialog(JWebBrowser.this,
                  "enter HTTP agent identification:",
                  System.getProperty("http.agent", "Java1.4.0"));
          if (p != null) System.setProperty("http.agent", p);
        }
      });
      item.setMnemonic(KeyEvent.VK_S);
      optionMenu.add(item);

      item = new JMenuItem("validate links in page");
      item.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent e) {
          validateLinks(current);
        }
      });
      item.setMnemonic(KeyEvent.VK_V);
      optionMenu.add(item);

      item = new JMenuItem("clear cache");
      item.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent e) {
          synchronized (cache) {
            Iterator i = cache.keySet().iterator();
            while (i.hasNext()) {
              ((URLCache) cache.get((URL) i.next())).clearCache();
            }
          }
        }
      });
      item.setMnemonic(KeyEvent.VK_V);
      optionMenu.add(item);
    }
    JMenu winMenu = new JMenu("Window");
    winMenu.setMnemonic(KeyEvent.VK_W);
    menuBar.add(winMenu);
    {
      winMenu.add(Menus.createLookAndFeelMenu(this));
    }
    JMenu helpMenu = new JMenu("Help");
    helpMenu.setMnemonic(KeyEvent.VK_H);
    helpMenu.add(Menus.createAboutDialogMenuItem(this));
    menuBar.add(helpMenu);
    return menuBar;
  }

  JPopupMenu getPopupMenu() {
    JPopupMenu miniMenu = new JPopupMenu();
    JMenuItem item;

    item = new JMenuItem("HTML code");
    item.addActionListener(new ActionListener() {
      public void actionPerformed(ActionEvent e) {
        viewHTML();
      }
    });
    item.setMnemonic(KeyEvent.VK_H);
    miniMenu.add(item);

    item = new JMenuItem("plain text");
    item.addActionListener(new ActionListener() {
      public void actionPerformed(ActionEvent e) {
        viewTextOnly();
      }
    });
    item.setMnemonic(KeyEvent.VK_T);
    miniMenu.add(item);

    item = new JMenuItem("links");
    item.addActionListener(new ActionListener() {
      public void actionPerformed(ActionEvent e) {
        viewLinkList();
      }
    });
    item.setMnemonic(KeyEvent.VK_L);
    miniMenu.add(item);

    item = new JMenuItem("embedded images");
    item.addActionListener(new ActionListener() {
      public void actionPerformed(ActionEvent e) {
        viewImageList();
      }
    });
    item.setMnemonic(KeyEvent.VK_I);
    miniMenu.add(item);

    return miniMenu;
  }

  JToolBar getToolBar() {
    JToolBar tools = new JToolBar();
    tools.setRollover(true);
    //tools.setMargin(new Insets(1, 1, 1, 1));
    ImageIcon icon = new ImageIcon(Settings.getResource("org/jscience/awt/icons/navigation/Back16.gif"));
    JButton button = new JButton(icon);
    button.setToolTipText("Back");
    button.setMnemonic(KeyEvent.VK_B);
    button.addActionListener(new ActionListener() {
      public void actionPerformed(ActionEvent e) {
        back();
      }
    });
    tools.add(button);
    icon = new ImageIcon(Settings.getResource("org/jscience/awt/icons/navigation/Forward16.gif"));
    button = new JButton(icon);
    button.setToolTipText("Forward");
    button.setMnemonic(KeyEvent.VK_R);
    button.addActionListener(new ActionListener() {
      public void actionPerformed(ActionEvent e) {
        forward();
      }
    });
    tools.add(button);
    icon = new ImageIcon(Settings.getResource("org/jscience/awt/icons/navigation/Home16.gif"));
    button = new JButton(icon);
    button.setToolTipText("Home");
    button.setMnemonic(KeyEvent.VK_M);
    button.addActionListener(new ActionListener() {
      public void actionPerformed(ActionEvent e) {
        setPage(home);
      }
    });
    tools.add(button);
    icon = new ImageIcon(Settings.getResource("org/jscience/awt/icons/general/Refresh16.gif"));
    button = new JButton(icon);
    button.setToolTipText("Refresh");
    button.setMnemonic(KeyEvent.VK_R);
    button.addActionListener(new ActionListener() {
      public void actionPerformed(ActionEvent e) {
        refresh();
      }
    });
    tools.add(button);
    icon = new ImageIcon(Settings.getResource("org/jscience/awt/icons/general/Stop16.gif"));
    stopButton = new JButton(icon);
    stopButton.setToolTipText("Stop");
    stopButton.setMnemonic(KeyEvent.VK_S);
    stopButton.addActionListener(new ActionListener() {
      public void actionPerformed(ActionEvent e) {
        stopLoading();
      }
    });
    stopButton.setEnabled(false);
    tools.add(stopButton);
    tools.addSeparator();
    textUrlField.addActionListener(new ActionListener() {
      public void actionPerformed(ActionEvent e) {
        try {
          setPage(new URL(textUrlField.getText()));
        } catch (MalformedURLException ex) {
          try {
            setPage(new URL("http://" + textUrlField.getText()));
          } catch (MalformedURLException exc) {
            updateStatusText("entered URL invalid");
          }
        }
      }
    });
    tools.add(textUrlField);
    return tools;
  }

  /**
   * shows a window with only the text stripped from the HTML
   */
  protected void viewTextOnly() {
    try {
      JTextArea text = new JTextArea(current.stripText());
      final JDialog dialog = new JDialog(this, "plain text", true);
      dialog.getContentPane().setLayout(new BorderLayout());
      JScrollPane pane = new JScrollPane(text);
      Dimension d = new Dimension((int) getSize().getWidth(),
              (int) (getSize().getHeight() * 0.7));
      pane.setPreferredSize(d);
      dialog.getContentPane().add(pane, BorderLayout.CENTER);
      dialog.getContentPane().add(new CloseButton(dialog), BorderLayout.SOUTH);
      dialog.pack();
      dialog.setLocationRelativeTo(this);
      dialog.setVisible(true);
    } catch (IOException e) {
      updateStatusText("could not load text");
      return;
    }
  }

  /**
   * shows a window with the HTML code
   */
  protected void viewHTML() {
    try {
      JTextArea text = new JTextArea(current.getContentAsString());
      final JDialog dialog = new JDialog(this, "HTML code", true);
      dialog.getContentPane().setLayout(new BorderLayout());
      JScrollPane pane = new JScrollPane(text);
      Dimension d = new Dimension((int) getSize().getWidth(),
              (int) (getSize().getHeight() * 0.7));
      pane.setPreferredSize(d);
      dialog.getContentPane().add(pane, BorderLayout.CENTER);
      dialog.getContentPane().add(new CloseButton(dialog), BorderLayout.SOUTH);
      dialog.pack();
      dialog.setLocationRelativeTo(this);
      dialog.setVisible(true);
    } catch (IOException e) {
      updateStatusText("could not HTML code");
      return;
    }
  }

  /**
   * shows a window with the embedded images from the current page
   */
  protected void viewImageList() {
    final JDialog dialog = new JDialog(this, "embedded images", false);
    dialog.getContentPane().setLayout(new BorderLayout());
    final Stack<ImageViewer> viewers = new Stack<ImageViewer>();
    final JList list;
    try {
      list = new JList(URLSorter.sort(current.getImages()));
    } catch (IOException e) {
      JOptionPane.showMessageDialog(this, e.getMessage(),
              "cannot retrieve images", JOptionPane.ERROR_MESSAGE);
      //updateStatusText(" ");
      return;
    }
    list.addMouseListener(new MouseAdapter() {
      public void mouseClicked(MouseEvent e) {
        if (e.getClickCount() == 2) {
          URL url = (URL) list.getSelectedValue();
          ImageIcon icon = new ImageIcon(url);
          ImageViewer v = new ImageViewer(icon, url.toString());
          viewers.add(v);
          v.setVisible(true);
        }
      }

      public void mousePressed(MouseEvent e) {
        popup(e);
      }

      public void mouseReleased(MouseEvent e) {
        popup(e);
      }

      void popup(MouseEvent e) {
        if (e.isPopupTrigger()) {
          JPopupMenu menu = new JPopupMenu();
          JMenuItem item = new JMenuItem("save image");
          item.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
              URL url = (URL) list.getSelectedValue();
              if (url == null) {
                JOptionPane.showMessageDialog(dialog, "no image selected");
              } else {
                download(url);
              }
            }
          });
          menu.add(item);
          menu.show(e.getComponent(), e.getX(), e.getY());
        }
      }
    });
    dialog.getContentPane().add(new JScrollPane(list), BorderLayout.CENTER);
    JButton button = new JButton("Close");
    button.setMnemonic(KeyEvent.VK_C);
    button.addActionListener(new ActionListener() {
      public void actionPerformed(ActionEvent e) {
        for (int i = 0; i < viewers.size(); i++) {
          ((ImageViewer) viewers.get(i)).setVisible(false);
          ((ImageViewer) viewers.get(i)).dispose();
        }
        dialog.setVisible(false);
      }
    });
    dialog.getContentPane().add(button, BorderLayout.SOUTH);
    dialog.pack();
    dialog.setLocationRelativeTo(this);
    dialog.setVisible(true);
    //updateStatusText(" ");
  }

  /**
   * shows a window with the links from the given page
   * (as probably not all links are accessible via hyperlink from the
   * JEditorPane)
   */
  protected void viewLinkList() {
    final JDialog dialog = new JDialog(this, "link list", true);
    dialog.getContentPane().setLayout(new BorderLayout());
    final JList list;
    try {
      list = new JList(URLSorter.sort(current.getLinks()));
    } catch (IOException e) {
      JOptionPane.showMessageDialog(this, e.getMessage(),
              "cannot retrieve links", JOptionPane.ERROR_MESSAGE);
      //updateStatusText(" ");
      return;
    }
    list.addMouseListener(new MouseAdapter() {
      public void mouseClicked(MouseEvent e) {
        if (e.getClickCount() == 2) {
          setPage((URL) list.getSelectedValue());
        }
      }

      public void mousePressed(MouseEvent e) {
        popup(e);
      }

      public void mouseReleased(MouseEvent e) {
        popup(e);
      }

      void popup(MouseEvent e) {
        if (e.isPopupTrigger()) {
          JPopupMenu menu = new JPopupMenu();
          JMenuItem item = new JMenuItem("save link");
          item.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
              URL url = (URL) list.getSelectedValue();
              if (url == null) {
                JOptionPane.showMessageDialog(dialog, "no link selected");
              } else {
                download(url);
              }
            }
          });
          menu.add(item);
          item = new JMenuItem("open in new window");
          item.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
              URL url = (URL) list.getSelectedValue();
              if (url == null) return;
              JWebBrowser jwb = new JWebBrowser(url);
              jwb.setDefaultCloseOperation(DISPOSE_ON_CLOSE);
              jwb.setVisible(true);
            }
          });
          menu.add(item);
          menu.show(e.getComponent(), e.getX(), e.getY());
        }
      }
    });
    dialog.getContentPane().add(new JScrollPane(list), BorderLayout.CENTER);
    dialog.getContentPane().add(new CloseButton(dialog), BorderLayout.SOUTH);
    dialog.pack();
    dialog.setLocationRelativeTo(this);
    dialog.setVisible(true);
    //updateStatusText(" ");
  }

  /**
   * shows a window with the broken links in this page
   */
  protected void validateLinks(final URLCache uc) {
    if (busy) return;
    busy = true;
    new Thread() {
      public void run() {
        validateLinksInThread(uc);
      }
    }.start();
    updateStatusText("validating links ..");
  }

  /**
   * executes outside the event handler thread
   */
  private void validateLinksInThread(URLCache uc) {
    final URL[] broken;
    try {
      broken = URLSorter.sort(new Spider(uc.getURL()).getBrokenLinks());
    } catch (IOException e) {
      JOptionPane.showMessageDialog(this, e.getMessage(),
              "cannot verify links", JOptionPane.ERROR_MESSAGE);
      updateStatusText(" ");
      return;
    }
    if (broken.length == 0) {
      JOptionPane.showMessageDialog(this, "no broken links in current page",
              "links validated", JOptionPane.INFORMATION_MESSAGE);
      updateStatusText(" ");
      return;
    }
    Runnable showDialog = new Runnable() {
      public void run() {
        // this is going to be performed in the event handler thread again
        JDialog dialog = new JDialog(JWebBrowser.this, "broken links", true);
        dialog.getContentPane().setLayout(new BorderLayout());
        JList list = new JList(broken);
        dialog.getContentPane().add(new JScrollPane(list), BorderLayout.CENTER);
        dialog.getContentPane().add(new CloseButton(dialog), BorderLayout.SOUTH);
        dialog.pack();
        dialog.setLocationRelativeTo(JWebBrowser.this);
        dialog.setVisible(true);
        updateStatusText(" ");
        busy = false;
      }
    };
    SwingUtilities.invokeLater(showDialog);
  }

  /**
   * implements the action for the browser's refresh button
   */
  public void refresh() {
    URLCache tmp = current;
    current.clearCache();
    setPage(blankPage);
    busy = false;
    setPage(tmp);
  }

  /**
   * sets the current page for the browser's main window;
   * the call may be ignored if the browser is currently
   * busy loading another page (preventing multiple loads)
   */
  public void setPage(URL url) {
    URLCache uc;
    synchronized (cache) {
      if (cache.containsKey(url)) {
        uc = (URLCache) cache.get(url);
      } else {
        uc = new URLCache(url);
        cache.put(url, uc);
      }
    }
    history.push(current);
    forwards.clear();
    setPage(uc);
  }

  /**
   * only to be called by back(), forward() and refresh(),
   * as it doesn't maintain history; use setPage(URL) otherwise
   */
  private void setPage(final URLCache uc) {
    if (busy) return;
    busy = true;
    new Thread() {
      public void run() {
        loadPageInThread(uc);
      }
    }.start();
    nowLoading = uc;
    stopButton.setEnabled(true);
    updateStatusText("loading page ..");
  }

  /**
   * executes outside the event handler thread and is only called by setPage(URLCache)
   */
  private void loadPageInThread(final URLCache uc) {
    // loading URL into cache
    uc.waitForRefresh();
    stopButton.setEnabled(false);
    // put the remainder back in the event handler thread
    Runnable showstuff = new Runnable() {
      public void run() {
        try {
          String type = uc.getContentType();
          if ((type != null) && (type.indexOf("mage/") > 0)) {
            ImageViewer iv = new ImageViewer(new ImageIcon(uc.getURL()), uc.getURL().toString());
            iv.setVisible(true);
            updateStatusText("displaying image in external viewer");
            busy = false;
            return;
          }
          // textPane.setPage(uc);
          textPane.setPage(uc.getURL());
          current = uc;
          textUrlField.setText(current.getURL().toString());
          updateStatusText("page loaded: " + ((current.getTitle().length() == 0) ?
                  "(no title)" : current.getTitle()));
        } catch (IOException e) {
          // todo
          //textPane.setPage((URL)null);
          current = uc;
          textUrlField.setText(current.getURL().toString());
          updateStatusText("page loaded with error: " + current.getURL().toString());
          JOptionPane.showMessageDialog(JWebBrowser.this, e.getMessage(),
                  "page load error", JOptionPane.ERROR_MESSAGE);
          updateStatusText(" ");
        }
        busy = false;
      }
    };
    SwingUtilities.invokeLater(showstuff);
  }

  /**
   * implements the action for the browser's stop button
   */
  public void stopLoading() {
    if (!stopButton.isEnabled()) return;
    stopButton.setEnabled(false);
    nowLoading.stopCurrentRefresh();
  }

  /**
   * downloads the given URL with a JDownloader after the GUI
   * asked for the file name
   *
   * @see JDownloader
   */
  protected void download(URL url) {
    if (url == null) return;
    URLCache uc;
    synchronized (cache) {
      if (cache.containsKey(url)) {
        uc = (URLCache) cache.get(url);
      } else {
        uc = new URLCache(url);
        cache.put(url, uc);
      }
    }
    download(uc);
  }

  void download(final URLCache uc) {
    if (uc == null) return;
    if (busy) return;
    fchooser.setDialogTitle("download URL");
    if (uc.getURL().getProtocol().equals("mailto")) {
      JOptionPane.showMessageDialog(this, "cannot download email links");
      updateStatusText(" ");
      return;
    }
    String path = uc.getURL().toExternalForm();
    path = path.substring(path.lastIndexOf("/"));
    if (path.length() < 2) path = "default.html";
    fchooser.setSelectedFile(new File(fchooser.getCurrentDirectory(), path));
    int option = fchooser.showSaveDialog(this);
    if (option == fchooser.APPROVE_OPTION) {
      if (!uc.isCached()) uc.refresh();
      File file = fchooser.getSelectedFile();
      new JDownloader(this, uc, file).start();
    }
  }

  /**
   * implements the action for the browser's back button
   */
  public void back() {
    if (busy) return;
    if (history.size() > 0) {
      setPage((URLCache) history.peek());
      forwards.push(current);
      current = (URLCache) history.pop();
      textUrlField.setText(current.getURL().toString());
    }
  }

  /**
   * implements the action for the browser's forward button
   */
  public void forward() {
    if (busy) return;
    if (forwards.size() > 0) {
      setPage((URLCache) forwards.peek());
      history.push(current);
      current = (URLCache) forwards.pop();
      textUrlField.setText(current.getURL().toString());
    }
  }

  /**
   * returns the page currently set as the home page
   */
  public URL getHome() {
    return home;
  }

  /**
   * returns the list of favorites
   */
  public URL[] getFavorites() {
    return (URL[]) favorites.toArray(new URL[favorites.size()]);
  }

  /* sets the home page that can be accessed using the browser's home button */
  public void setHome(URL homeURL) {
    if (homeURL == null) throw new IllegalArgumentException();
    home = homeURL;
  }

  /**
   * returns the page currently displayed
   */
  public URL getCurrentURL() {
    return current.getURL();
  }

  /**
   * returns a map of URL objects to URLCache objects
   */
  public Map getCache() {
    return cache;
  }

  /**
   * starts the JWebBrowser and makes it visible;
   * you can optionally specify a URL as parameter
   */
  public static void main(String[] args) throws Exception {
    if (args.length > 0) {
      new JWebBrowser(new URL(args[0])).setVisible(true);
    } else {
      new JWebBrowser().setVisible(true);
    }
  }
}