Rendering of Java Swing GUI in Lobo Web Browser

The Lobo Project

Lobo@SF

Direct Java (Swing or AWT) Rendering in Lobo

Lobo 0.98+ [download] can directly render Java/Swing source files. Lobo treats Java as a first-class citizen, in much the same manner it treats HTML. This means that:

The deploy-test cycle of client-side Java code in Lobo is quicker and more convenient. There is no need to pre-compile and package Java code or use HTML pages.
The source code of a Java class is available for browser users to examine.
Java code in Lobo has access to various capabilities of the browser and can be more web oriented.
Lobo can load Java source code generated by server-side technology such as JSP, PHP, RoR and others.
Java code loaded by Lobo is potentially indexable by search engines.

Requirements

Direct Java rendering in Lobo requires JRE 1.6+, even though the browser itself only requires JRE 1.5+.

Security Restrictions

JavaFX/Java code loaded by Lobo from a remote location is run with security restrictions equivalent to those of an unsigned applet. Note, however, that Lobo provides capabilities that are not currently available to applets, such as managed stores.

MIME Type

The MIME type of a Java source document is expected to be text/x-java-source, but other MIME types like application/octet-stream and text/plain will work provided the URL ends in .java.

Java APIs Available in Lobo

A Java class loaded by Lobo should be assumed to only have access to the following APIs:

Java Platform SE 6 API.
Lobo Extensions and Clientlets API (lobo-pub.jar).
Classes from locations specified in the classpath or sourcepath directives (explained below).

Directives

Java/JavaFX "pages" in Lobo use standard Java/JavaFX syntax. You can, nevertheless, add a special comment that contains compilation and rendering directives for Lobo. The comment starts with /*! and ends with */. The content of the comment should be in property-file syntax, except an asterisk is allowed at the beginning of every line. Directives (properties) understood by Lobo, all optional, include:

title: The title of the "page". This should be the window title when the page is rendered, and it's also used in history lists and so on.
description: A description of the "page". This is saved along with Lobo bookmarks and is potentially indexable by search engines.
sourcepath: A list of comma-separated URLs required to locate other source files during compilation.
classpath: A list of comma-separated URLs, typically JAR file locations, required by the "page" at run-time.
sourcelist: If sourcepath contains URLs ending in slash (directories instead of JAR files) this property should contain a list of comma-separated file paths required during the build of the main compilation unit. A file path consists of the package name, with its dots replaced by forward slashes, followed by a forward slash and the file name, e.g. com/acme/package/File.java or com/acme/package/File.fx.
classlist: If classpath contains URLs ending in slash (directories instead of JAR files) this property should contain a list of comma-separated file paths required during the build of the main compilation unit. A file path consists of the package name, with its dots replaced by forward slashes, followed by a forward slash and the file name, e.g. com/acme/package/File.class.
use-preferred-size: If true, the component is rendered using its preferred size, if possible, and centered in the page. Otherwise, the component's size is the same as the page's.

Clientlet Context Access

A request-response thread in Lobo has access to the current ClientletContext instance, obtained by calling ClientletAccess.getCurrentClientletContext(). This can be used by scripts to perform various browser tasks, such as navigating away from the page, opening alert windows, making requests through Lobo, creating browser frames, or accessing managed stores.

What is Rendered

Obviously, only certain classes can be rendered: Those that can be assigned to java.awt.Component (including javax.swing.JComponent and java.awt.Window) plus any JavaFX classes assignable to Stage, Scene or Node.

Programmatic use of Lobo

We have a Browser API (GPL) that will load Java/JavaFX code, much like it loads HTML, provided the pertinent browser extensions are available at run-time. This means a Swing application can embed Lobo and load remote JavaFX/Java code via the Lobo API.

Examples

The following examples are not intended to be Java examples. These are examples of some basic things you can do with Java in Lobo.

Visit a page when a button is pressed.
This is a very simple example whereby navigation is redirected to a URL entered in a text field when the user presses a button.
NavigateTo.java
package org.lobobrowser.www; import javax.swing.*; import java.awt.*; import java.awt.event.*; import org.lobobrowser.clientlet.*; public class MyPanel extends JPanel { // Constructor should be executed in request thread. private final ClientletContext CTX = ClientletAccess.getCurrentClientletContext(); public MyPanel() { this.setBackground(Color.GREEN); this.setLayout(new FlowLayout()); final JTextField textField = new JTextField("http://google.com"); textField.setColumns(40); JButton button = new JButton("GO"); this.add(textField); this.add(button); button.addActionListener(new ActionListener() { public void actionPerformed(ActionEvent event) { try { CTX.navigate(textField.getText()); } catch(java.net.MalformedURLException mfu) { CTX.alert("Oops, bad URL!"); } } }); }
Using a third-party library.
This example makes use of JFreeChart to display a simple three-dimensional pie chart. The first time this program is loaded, you will note library JAR files are loaded from the website where the page resides. On subsequent page loads, JAR files should be retrieved from the Lobo cache.
ChartDemo.java
/*! * title: JFreeChart in Lobo * # Need JFreeChart in ClassPath. * # JAR files (1.2Mb total) are on the website. * classpath: /ext/lib/jcommon-1.0.0-rc1.jar,\ * /ext/lib/jfreechart-1.0.0-rc1.jar */ package org.lobobrowser.www; import javax.swing.*; import java.awt.*; import java.awt.geom.*; import org.jfree.chart.*; import org.jfree.data.general.*; public class ChartDemo extends JComponent { public void paintComponent(Graphics g1) { Graphics2D g = (Graphics2D) g1; DefaultPieDataset dataSet = new DefaultPieDataset(); dataSet.setValue("Group A", 20.0); dataSet.setValue("Group B", 30.0); dataSet.setValue("Group C", 60.0); JFreeChart chart = ChartFactory.createPieChart3D("Pie Chart 3D Demo", dataSet, true, true, false); chart.draw(g, this.getBounds().getBounds2D()); } }
This is how ChartDemo.java renders in Lobo:

Feedback

If you have successfully tried Java or JavaFX code in Lobo, feel free to post your source code URLs at the Open Discussion Forum.

If something doesn't work quite right in Lobo's support of Java/JavaFX, please use the Help Forum to tell us.