Cobra: Getting Started

Test Program

set CLASSPATH=cobra.jar;js.jar
java org.lobobrowser.html.test.TestEntry

A few other test tools are available, such as the ParserTest class which may be used to test the Cobra HTML parser independently of the renderer.

API Documentation

HTML Parser Usage

Simple Rendering Engine Usage

import org.lobobrowser.html.parser.*;
import org.lobobrowser.html.test.*;
import org.lobobrowser.html.gui.*;
import org.lobobrowser.html.*;
import org.w3c.dom.*;
...
HtmlPanel panel = new HtmlPanel();
// This panel should be added to a JFrame or
// another Swing component.
UserAgentcontext ucontext = new SimpleUserAgentContext();
SimpleHtmlRendererContext rcontext = new SimpleHtmlRendererContext(panel, ucontext);
// Note that document builder should receive both contexts.
DocumentBuilderImpl dbi = new DocumentBuilderImpl(ucontext, rcontext);
// A documentURI should be provided to resolve relative URIs.
Document document = dbi.parse(new InputSourceImpl(documentReader, documentURI));
// Now set document in panel. This is what causes the document to render.
panel.setDocument(document, rcontext);

Incremental Rendering

Instead of parsing the whole document before passing it to HtmlPanel, you can create an empty one by calling createDocument instead. This will return an instance of HTMLDocumentImpl. Next, you set the document in HtmlPanel by calling setDocument. Finally, you parse the document (which should be done outside the GUI dispatch thread) by calling HTMLDocumentImpl.load.

If you need to listen on document modification notifications as the document loads, see the addDocumentNotificationListener method.

The navigate method of SimpleHtmlRendererContext implements a simple incremental HTML rendering routine.

Examples

1. Bare minimum renderer.
   This example contains the minimum necessary code to open a JFrame and render a HTML page (our browser home page in this case) with Cobra.

   BareMinimumTest.java
   import javax.swing.*; import org.lobobrowser.html.gui.*; import org.lobobrowser.html.test.*; public class BareMinimumTest { public static void main(String[] args) throws Exception { JFrame window = new JFrame(); HtmlPanel panel = new HtmlPanel(); window.getContentPane().add(panel); window.setSize(600, 400); window.setVisible(true); new SimpleHtmlRendererContext(panel, new SimpleUserAgentContext()) .navigate("http://lobobrowser.org/browser/home.jsp"); } }

2. Parsing and rendering with preferred width.
   This example is more elaborate and it shows (1) how to disable most Cobra logging, (2) how the caller can parse a HTML page and create a document instance, (3) how to create a window with a preferred width, whose preferred size is determined by the HTML content, and (4) how to override Cobra routines to open a new browser window on Javascript window.open() calls.

   BarebonesTest.java
   import java.io.InputStream; import java.io.InputStreamReader; import java.io.Reader; import java.net.URL; import java.net.URLConnection; import java.awt.*; import java.util.logging.*; import javax.swing.*; import org.w3c.dom.Document; import org.w3c.dom.html2.HTMLElement; import org.xml.sax.InputSource; import org.lobobrowser.html.*; import org.lobobrowser.html.gui.*; import org.lobobrowser.html.parser.*; import org.lobobrowser.html.test.*; public class BarebonesTest { public static void main(String[] args) throws Exception { // Initialize logging so only Cobra warnings are seen. Logger.getLogger("org.lobobrowser") .setLevel(Level.WARNING); // Open a connection on the URL we want to render first. String uri = "http://lobobrowser.org/browser/home.jsp"; URL url = new URL(uri); URLConnection connection = url.openConnection(); InputStream in = connection.getInputStream(); // A Reader should be created with the correct charset, // which may be obtained from the Content-Type header // of an HTTP response. Reader reader = new InputStreamReader(in); // InputSourceImpl constructor with URI recommended // so the renderer can resolve page component URLs. InputSource is = new InputSourceImpl(reader, uri); HtmlPanel htmlPanel = new HtmlPanel(); UserAgentContext ucontext = new LocalUserAgentContext(); HtmlRendererContext rendererContext = new LocalHtmlRendererContext(htmlPanel, ucontext); // Set a preferred width for the HtmlPanel, // which will allow getPreferredSize() to // be calculated according to block content. // We do this here to illustrate the // feature, but is generally not // recommended for performance reasons. htmlPanel.setPreferredWidth(800); // Note: This example does not perform incremental // rendering while loading the initial document. DocumentBuilderImpl builder = new DocumentBuilderImpl( rendererContext.getUserAgentContext(), rendererContext); Document document = builder.parse(is); in.close(); // Set the document in the HtmlPanel. This method // schedules the document to be rendered in the // GUI thread. htmlPanel.setDocument(document, rendererContext); // Create a JFrame and add the HtmlPanel to it. final JFrame frame = new JFrame(); frame.getContentPane().add(htmlPanel); // We pack the JFrame to demonstrate the // validity of HtmlPanel's preferred size. // Normally you would want to set a specific // JFrame size instead. // pack() should be called in the GUI dispatch // thread since the document is scheduled to // be rendered in that thread, and is required // for the preferred size determination. EventQueue.invokeLater(new Runnable() { public void run() { frame.pack(); frame.setVisible(true); } }); } private static class LocalUserAgentContext extends SimpleUserAgentContext { // Override methods from SimpleUserAgentContext to // provide more accurate information about application. public LocalUserAgentContext() { } public String getAppMinorVersion() { return "0"; } public String getAppName() { return "BarebonesTest"; } public String getAppVersion() { return "1"; } public String getUserAgent() { return "Mozilla/4.0 (compatible;) CobraTest/1.0"; } } private static class LocalHtmlRendererContext extends SimpleHtmlRendererContext { // Override methods from SimpleHtmlRendererContext // to provide browser functionality to the renderer. public LocalHtmlRendererContext(HtmlPanel contextComponent, UserAgentContext ucontext) { super(contextComponent, ucontext); } public void linkClicked(HTMLElement linkNode, URL url, String target) { super.linkClicked(linkNode, url, target); // This may be removed: System.out.println("## Link clicked: " + linkNode); } public HtmlRendererContext open(URL url, String windowName, String windowFeatures, boolean replace) { // This is called on window.open(). HtmlPanel newPanel = new HtmlPanel(); JFrame frame = new JFrame(); frame.setSize(600, 400); frame.getContentPane().add(newPanel); HtmlRendererContext newCtx = new LocalHtmlRendererContext(newPanel, this.getUserAgentContext()); newCtx.navigate(url, "_this"); return newCtx; } } }

Interface Implementations

The Lobo Browser API (GPL) is a separate API library we provide. This is a browser API as opposed to an HTML API. It uses Cobra as part of its HTML extension. In situations where users need to embed a browser in a Swing application, without concern for the way browser features are implemented, the Lobo Browser API is a good alternative to Cobra.

Help

If you find something doesn't work quite the way it should, please submit a bug report or a feature request.

See Also

• Cobra Home Page
• Cobra HTML DOM Parser Information
• Lobo Browser API Information

Support The Project

• Make a donation.
• Contribute your time.