Simple Web Browser in Java

Submitted by mehfuza on Sunday, September 8, 2013 - 18:16.

In this tutorial we will see how to create a simple web browser. It contains an address bar where a user can type the address and a go button which when clicked loads the web page. For displaying the web pages we require JEditor Pane and HyperlinkListener is required to respond when the user clicks on a link in the document. Following are the steps for creating the web browser. Step 1: Defining the constructor of the class The main class extends the JPanel. First we will set it's background color and layout as a Border Layout ans set border for it as follows.

      setBackground(Color.BLACK);
      setLayout(new BorderLayout(1,1));
      setBorder(BorderFactory.createLineBorder(Color.BLACK,1));

Scroll Pane is added to the edit pane and hyperlink listener is registered with this class. Edit Pane is placed in the center of the panel.

 
      editPane = new JEditorPane();
      editPane.setEditable(false);
      editPane.addHyperlinkListener(new LinkListener());
      add(new JScrollPane(editPane),BorderLayout.CENTER);

Next a toolbar is created and added to the north of the panel. A label, text field for location input and go button are added to this tool bar. Action Listener is added to the go button and location input field to load the url.

JToolBar toolbar = new JToolBar();
      toolbar.setFloatable(false);
      add(toolbar,BorderLayout.NORTH);
      ActionListener goListener = new GoListener();
      locationInput = new JTextField("www.sourcecodester.com", 40); //home page
      locationInput.addActionListener(goListener);
      JButton goButton = new JButton(" Go ");
      goButton.addActionListener(goListener);
      toolbar.add( new JLabel(" Location: "));
      toolbar.add(locationInput);
      toolbar.addSeparator(new Dimension(5,0)); //after 5 pixel of space the go button is added
      toolbar.add(goButton);

Step 2: Implementing Hyperlink Listener Hyperlink Listener contains a single function as hyperlinkUpdate() which is defined as follows. If hyperlink is clicked then URL of that hyperlink is loaded in the edit pane by calling loadURL() method.

public void hyperlinkUpdate(HyperlinkEvent evt) {
         if (evt.getEventType() == HyperlinkEvent.EventType.ACTIVATED) {
            loadURL(evt.getURL());
         }

Step 3: Defining loadURL() method It loads the document at the specified URL into the edit pane. try catch block is used to handle errors if occurred any while changing the contents of the edit pane. JEditPane's setPage() method is used to set the edit pane's content.

 private void loadURL(URL url) {
      try {
         editPane.setPage(url);
      }
      catch (Exception e) {
         editPane.setContentType("text/plain");
         editPane.setText( "Sorry, the requested document was not found\n"
               +"or cannot be displayed.\n\nError:" + e);
      }
   }

Step 4: ActionListener for Go button and Location input field Here the location input field's data is stored in a string variable and checked whether its format is wrong or right. If the format is correct then URL is created and loadURL() method is called to load that URL else suitable message is displayed.

public void actionPerformed(ActionEvent evt) {
         URL url;
         try {
            String location = locationInput.getText().trim(); //gets the text and removes the spaces 
            if (location.length() == 0) //empty URL
               throw new Exception();
            if (! location.contains("://")) // "://" if it not present in the string
               location = "http://" + location;
            url = new URL(location);  //create url from string
         }
         catch (Exception e) {
            JOptionPane.showMessageDialog(SimpleWebBrowser.this, 
                  "The Location input box does not\nccontain a legal URL.");
            return;
         }
         loadURL(url);
         locationInput.selectAll(); 
         locationInput.requestFocus();
      }

Step 5: main() for defining different properties of frame A frame is created and object of the main class(SimpleWebBrowser) is set as content of the frame as it is a panel. Location of the frame is centered using Toolkit as follows.

public static void main(String[] args) {
      JFrame window = new JFrame("SimpleWebBrowser"); // Title of web browser
      SimpleWebBrowser content = new SimpleWebBrowser();
      window.setContentPane(content);
      window.setSize(600,500);
      Dimension screenSize = Toolkit.getDefaultToolkit().getScreenSize();
      window.setLocation( (screenSize.width - window.getWidth())/2, (screenSize.height - window.getHeight())/2 );//center the frame
      window.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE );
      window.setVisible(true);
   }