Rendering HTML in Java

Question

I am trying to create a help panel for an application I am working on. The help file as already been created using html technology and I would like it to be rendered in a pane and shown. All the code I have seen shows how to render a site e.g. "http://google.com". I want to render a file from my pc e.g. "file://c:\tutorial.html"

This is the code i have, but it doesn't seem to be working.

import javax.swing.JEditorPane;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JScrollPane;
import javax.swing.SwingUtilities;
import java.awt.Color;
import java.awt.Container;
import java.io.IOException;

import static java.lang.System.err;
import static java.lang.System.out;

    final class TestHTMLRendering
        {
        // ------------------------------ CONSTANTS ------------------------------

        /**
         * height of frame in pixels
         */
        private static final int height = 1000;

        /**
         * width of frame in pixels
         */
        private static final int width = 1000;

        private static final String RELEASE_DATE = "2007-10-04";

        /**
         * title for frame
         */
        private static final String TITLE_STRING = "HTML Rendering";

        /**
         * URL of page we want to display
         */
        private static final String URL = "file://C:\\print.html";

        /**
         * program version
         */
        private static final String VERSION_STRING = "1.0";

        // --------------------------- main() method ---------------------------

        /**
         * Debugging harness for a JFrame
         *
         * @param args command line arguments are ignored.
         */
        @SuppressWarnings( { "UnusedParameters" } )
        public static void main( String args[] )
            {
            // Invoke the run method on the Swing event dispatch thread
            // Sun now recommends you call ALL your GUI methods on the Swing
            // event thread, even the initial setup.
            // Could also use invokeAndWait and catch exceptions
            SwingUtilities.invokeLater( new Runnable()
            {
            /**
             * } fire up a JFrame on the Swing thread
             */
            public void run()
                {
                out.println( "Starting" );
                final JFrame jframe =
                        new JFrame( TITLE_STRING + " " + VERSION_STRING );
                Container contentPane = jframe.getContentPane();
                jframe.setSize( width, height );

                contentPane.setBackground( Color.YELLOW );
                contentPane.setForeground( Color.BLUE );
                jframe.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE );
                try
                    {
                    out.println( "acquiring URL" );
                    JEditorPane jep = new JEditorPane( URL );
                    out.println( "URL acquired" );
                    JScrollPane jsp =
                            new JScrollPane( jep,
                                    JScrollPane.VERTICAL_SCROLLBAR_AS_NEEDED,
                                    JScrollPane.HORIZONTAL_SCROLLBAR_AS_NEEDED );
                    contentPane.add( jsp );
                    }
                catch ( IOException e )
                    {
                    err.println( "can't find URL" );
                    contentPane.add( new JLabel( "can't find URL" ) );
                    }
                jframe.validate();
                jframe.setVisible( true );
                // Shows page, with HTML comments erroneously displayed.
                // The links are not clickable.
                }
            } );
            }// end main
        }// end TestHTMLRendering

Answer 1

Rendering HTML in Swing is problematic. Swing components have some native support for HTML but it's not even HTML4. It's (limited!) HTML 3.2. If you use a different desktop library API you'll have much better options

• WebKit for SWT (ver. 0.6) for the Eclipse Standard Widget Tookit is an excellent option. As the name suggests, it plugs the WebKit rendering engine (which powers Chrome and Safari) into SWT;

• Netbeans Platform may have some options too.

You may also want to look at Flying Saucer, which is:

An XML/XHTML/CSS 2.1 Renderer

(in 100% Java)

Answer 2

What @cletus says is all true. If you want to get your current app going though with a file-based URL, try setting:

URL = "file:///C://print.html"

Answer 3

You forgot to set the content type of the JEditorPane.

jep.setContentType("text/html");