setProperty("headless","true") weirdness?

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Daisy - 08 Aug 2006 11:46 GMT

Can anyone provide insight on System.setProperty( "java.awt.headless" ,
"true" )?

I've been struggling with a HeadlessException in the line:
JFrame frame = new JFrame( );

So I added System.setProperty( "java.awt.headless" , "true" ) before
the JFrame call. However, JFrame still throws this error. Shouldn't
setting the property inform the JVM that it is headless?

System.setProperty( "java.awt.headless" , "true" );
try {
JFrame frame = new JFrame( );
frame.getContentPane( ).add( c );
frame.addNotify( );
} catch ( HeadlessException e ) {
printStackTrace( );
}

It is a Redhat computer running Hotspot 1.5.0_07 and Tomcat 5.5.17. It
is headless. The application is a servlet that runs fine on linux
machines with monitors. I tried the -Djava.awt.headless=true argument
long ago and still use it.

I'd really appreciate any insight on this problem,

Thanks!

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Gordon Beaton - 08 Aug 2006 12:03 GMT

> Can anyone provide insight on System.setProperty(
> "java.awt.headless" , "true" )?
[quoted text clipped - 5 lines]
> the JFrame call. However, JFrame still throws this error. Shouldn't
> setting the property inform the JVM that it is headless?

I believe you need to set the property before
java.awt.GraphicsEnvironment is loaded and initialized.

/gordon

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[ don't email me support questions or followups ]
g o r d o n + n e w s @ b a l d e r 1 3 . s e

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Stanimir Stamenkov - 08 Aug 2006 14:04 GMT

> I've been struggling with a HeadlessException in the line:
> JFrame frame = new JFrame( );
>
> So I added System.setProperty( "java.awt.headless" , "true" ) before
> the JFrame call. However, JFrame still throws this error. Shouldn't
> setting the property inform the JVM that it is headless?

I believe that's what we expect - you can't construct a Frame given
you're in a headless environment, why do you need to?

> HeadlessException - Thrown when code that is dependent on a
> keyboard, display, or mouse is called in an environment that does
> not support a keyboard, display, or mouse.

Signature

Stanimir

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Norman D. - 08 Aug 2006 14:15 GMT

Here is a link which might be helpful:

http://java.sun.com/developer/technicalArticles/J2SE/Desktop/headless/

--Norman

> Can anyone provide insight on System.setProperty( "java.awt.headless" ,
> "true" )?
[quoted text clipped - 23 lines]
>
> Thanks!

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Daisy - 11 Aug 2006 12:43 GMT

Thanks everyone who gave advice!

Here's the revised code which resolved the problem:

System.setProperty( "java.awt.headless" , "true" );
Toolkit tk = Toolkit.getDefaultToolkit( );

try {
// JFrame frame = new JFrame( );
// frame.getContentPane( ).add( c );

JPanel panel = new JPanel( );
panel.add( c );
panel.addNotify( );

In addition to setting the headless property, I had to swap from Frame
to Panel.

Thanks,

Jeff

> Here is a link which might be helpful:
>
[quoted text clipped - 29 lines]
> >
> > Thanks!

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setProperty("headless","true") weirdness?

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