URL class mystery

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Lou Lipnickey - 05 Nov 2004 04:32 GMT

I have a user (in a large university environment) that is using an
application which uses JEditorPane to display reports in HTML format.
Initiatially, the applicaton was set up with :
URL url = new URL("file:test.htm");
but this caused a URL exception, the exact likes of which I don't
exactly recall. To get around this problem, I changed the statement to :
URL("file","localhost","test.htm");
and the reports were displayed with no error messages. I had chaulked it
up to some unknown network thing in his environment. Now, however, I
would like to add reports which contain jpgs and I am finding the
URL("file","localhost","test.htm");
form does not render the jpgs, it gives the image not found symbol.
However, if you use:
URL("file","localhost","test.htm");
the jpgs are rendered fine.
Can anyone 1) explain what is going on and 2) suggest a work around.
Code for a test class follows, along with a simple HTML file. You can
supply your own jpg (in place of test.jpg). Any help would be greatly
appreciated. Thanks - Lou

import javax.swing.*;
import javax.swing.event.*;
import javax.swing.text.*;
import javax.swing.text.html.*;
import java.awt.*;
import java.awt.event.*;
import java.net.*;

public class HTML extends JFrame implements HyperlinkListener
{
public HTML() {
super("HTML Widget");

setVisible(false);
JPanel p = new JPanel(new BorderLayout());

try {
URL url = new URL("file:test.htm");

//URL url = new URL("file","localhost","test.htm");

JEditorPane jp = new JEditorPane();

jp.setEditable(false);
jp.addHyperlinkListener(this);
jp.setContentType("text/html");
jp.setPage(url);

JScrollPane scroller = new JScrollPane(jp);

p.add(scroller, BorderLayout.CENTER);

}
catch (Exception e) {
System.out.println("Unexpected error: " + e);
System.exit(0);
}

p.setPreferredSize(new Dimension(300,300));
setContentPane(p);

addWindowListener(new WindowAdapter() {
public void windowClosing(WindowEvent w) {
System.exit(0);
}
});

pack();
show();
}

/**
* Notification of a change relative to a hyperlink.
*/
public void hyperlinkUpdate(HyperlinkEvent e) {
HyperlinkEvent.EventType type = e.getEventType();

if (type == HyperlinkEvent.EventType.ACTIVATED) {
JEditorPane pane = (JEditorPane) e.getSource();

if (e instanceof HTMLFrameHyperlinkEvent) {
HTMLFrameHyperlinkEvent evt = (HTMLFrameHyperlinkEvent) e;
HTMLDocument doc = (HTMLDocument)
pane.getDocument();

doc.processHTMLFrameHyperlinkEvent(evt);
} else {
try {
pane.setPage(e.getURL());
} catch(Throwable t) {
t.printStackTrace();
}
}
}
}

public static void main(String args[]) {

HTML html = new HTML();
}
}

// End HTML.java

------------------------------------------------------
test.htm

<html>
<body>
<IMG SRC='test.jpg'>
</body>
</html

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Andrew Thompson - 05 Nov 2004 05:13 GMT

Your example works* here when I put test.htm in the same
directory as the application along with a suitably named image.

* The HTML document loads and displays the image.

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Rogan Dawes - 05 Nov 2004 10:05 GMT

> I have a user (in a large university environment) that is using an
> application which uses JEditorPane to display reports in HTML format.
[quoted text clipped - 15 lines]
> supply your own jpg (in place of test.jpg). Any help would be greatly
> appreciated. Thanks - Lou

You might want to check out the following article for some background of
how JEditorPane loads images. It might provide some insight into what
you are seeing:

http://www.javaworld.com/javaworld/javatips/jw-javatip109.html

Regards,

Rogan

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Lou Lipnickey - 05 Nov 2004 14:18 GMT

Did you uncomment the line:
URL url = new URL("file","localhost","test.htm");
(maybe I forgot to mention it)? Thats the one which is causing the
rendering issue. Thanks
Lou

>> I have a user (in a large university environment) that is using an
>> application which uses JEditorPane to display reports in HTML format.
[quoted text clipped - 25 lines]
>
> Rogan

Reply to this Message

Chris Smith - 07 Nov 2004 15:51 GMT

> I have a user (in a large university environment) that is using an
> application which uses JEditorPane to display reports in HTML format.
[quoted text clipped - 3 lines]
> exactly recall. To get around this problem, I changed the statement to :
> URL("file","localhost","test.htm");

Neither of those are the way I'd do things. Why not try:

URL url = new URL(new File("test.htm").toURI().toURL());

Of course, if "test.htm" is not in the current working directory, then
you'll need to give a full path or specify the base directory as a first
parameter to the File constructor. What the above code solves, though,
is any potential problem you might be having with the format of the
file-scheme URL. The formats can be difficult to keep straight between
various platforms, so why not let the API do it for you?

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Andrew Thompson - 07 Nov 2004 16:39 GMT

> Why not try:
>
> URL url = new URL(new File("test.htm").toURI().toURL());

I expect you meant..
URL url = new File("test.htm").toURI().toURL();

( Probably because that will not compile ;-)

I was about to add 'and that would require a signed applet..'
until I recalled the OP was talking about an application,
whereas I am used to dealing with JEP's in applets, where
"URL's rule!"

(snip)

> The formats can be difficult to keep straight between
> various platforms, so why not let the API do it for you?

A sterling idea!

( Sometimes I will whip up a quick 'main()' with a file object
just so I can see the format of the URL - for the umpteen
dozenth time.. )

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Reply to this Message

Chris Smith - 07 Nov 2004 18:19 GMT

> > Why not try:
> >
> > URL url = new URL(new File("test.htm").toURI().toURL());
>
> I expect you meant..
> URL url = new File("test.htm").toURI().toURL();

Yes, I did. Sorry for the confusion.

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www.designacourse.com
The Easiest Way To Train Anyone... Anywhere.

Chris Smith - Lead Software Developer/Technical Trainer
MindIQ Corporation

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URL class mystery

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