Re: Using images in JAR archives

From:

Nigel Wade <nmw@ion.le.ac.uk>

Newsgroups:

comp.lang.java.programmer

Date:

Wed, 20 Aug 2008 11:57:14 +0100

Message-ID:

<g8gtal$9f0$1@south.jnrs.ja.net>

Icarus wrote:

I've recently tried to export my current project as a JAR file.
However, whenever I now try to start it, I am getting a
NullpointerException from where the pictures are supposed to be.

Below's some code showing the problem. Iam using Eclipse for the
export. I already tried refreshing and using several versions of
getResource(), getSystemResource() and so on using relatie or absolute
paths. I even tried a version using an InputStream, the result is
always the same:

Exception in thread "main" java.lang.NullPointerException
        at javax.swing.ImageIcon.<init>(ImageIcon.java:138>
        at ShowImages.loadImage(ShowImages.java:25)
        at ShowImages.<init>(ShowImages.java:14)
        at ShowImages.main(ShowImages.java:31)

In Eclipse, the project works just fine. The pictures are placed in a
folder "images" in the JAR archive, as it should be. The manifest
reads:

Manifest-Version: 1.0
Main-Class: ShowImages

Do you have an idea on how to get this to work? If so, could you give
me an explanation on how you did it, using which options/commands?

import javax.swing.ImageIcon;
import javax.swing.JFrame;
import javax.swing.JLabel;

@SuppressWarnings("serial")
public class ShowImages extends JFrame {

      ShowImages(){
              this.setSize(500, 500);
              this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

              ImageIcon image1 = this.loadImage("images/image1.gif");

This is a relative path.

              JLabel label = new JLabel(image1);

              getContentPane().add(label);
              setVisible(true);
      }

      private ImageIcon loadImage(String path){
              java.net.URL url = ShowImages.class.getResource(path);

The above relative path is relative to the ShowImages class. This means that the
images directory must be in the same directory as the ShowImages.class file.

              ImageIcon titelbild = new ImageIcon(url);
              return titelbild;
      }

      public static void main(String[] args){
              ShowImages frame = new ShowImages();
      }
}

I prefer to use absolute paths in the jar file for images so I can place them
where I want in the jar filesystem. You say you've tried that but it didn't
work. It should do if you do it correctly. You need to show us the code which
failed.

This code works for me:

javax.swing.ImageIcon(getClass().getResource("/icons/stock-preferences.png"));

where the icons directory is in the root of the jar file

$ jar tf Administration.jar
....
icons/stock-preferences.png
....

--
Nigel Wade