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Plugging into Lobo's Pure Java Web Browser

· Java Zone

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Lobo's Java Web Browser, still at a dot zero release, drew my attention today because it very recently was Java Posse's project of the week. I love the fact that this browser is pure Java! Plus, it is open source and under active development. Let's help things along by explaining how to create plugins, because this project is smart enough to expose an API for this purpose.

At the end of this article, you'll be able to start up the Lobo browser and you will then see a new menu, with a new menu item, that will produce a "Hello World" greeting in a JOptionPane. It will all look thusly:

Even though there is no "Hello world" document for Lobo plugin development (which I am hoping to remedy by means of this article), the Lobo Browser Plugin HOWTO provides most of the information you need. It is all quite intuitive, once you have the basics. Here they are:

  1. After you download the Lobo distro, put its lobo-pub.jar on your plugin-to-be's classpath.
  2. At a bare minimum, you need a class that extends org.lobobrowser.ua.NavigatorExtension. Here's mine, just to give you an idea. Note the overrides, of course, because these are the main hooks into the browser:
    public class ExtensionImpl implements NavigatorExtension {

    private JMenu menu;
    private JMenuItem item;

    public void init(NavigatorExtensionContext ctx) {}

    public void windowOpening(NavigatorWindow window) {
    menu = new JMenu("Greetings");
    item = new JMenuItem("Hello");
    item.addActionListener(new ActionListener() {
    public void actionPerformed(ActionEvent arg0) {
    JOptionPane.showMessageDialog(null, "hello world");
    window.addMenu("Demo", menu);

    public void windowClosing(NavigatorWindow window) {}

    public void destroy() {}


    That's all we need for our small scenario. Since we're simply using Swing, it is easy to imagine other things that you might do when the window opens/closes, etc. Use code completion and other tools in your IDE to figure out other things you might be able to do to the Lobo browser:

  3. Now create a properties file called lobo-extension.properties, in your src structure, at the highest level, and add the following info:
    extension.name=Demo Lobo Extension
    extension.description=This is a demo extension
    extension.by=Geertjan Wielenga

    The extension class is the one shown in step 2, registered by its FQN. The priority is described in the API docs, it's not so important at this stage, since w're just doing a hello world scenario.

  4. Finally, you'll have a plugin that looks similar to this:

    Now compile the plugin, creating a JAR that you put in the distro's ext folder. Below, mine is called "DemoLoboPlugin.jar":

Just restart the browser and there's your new menu. Since it is this easy to extend the browser, I'm hoping this intro has grabbed your imagination and that you'll support this super cool browser. If you love Java, you'll love this browser. Downloading the distro and setting things up was as simple as unjarring and then running java -jar from the command line. Here's hoping that the people behind this project will publish MANY small samples demonstrating the ways in which the browser can be extended. That way, they'd be giving developers handholds to making this browser all that it should be.


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