Question

I’m new here and kinda new to java.
I’ve encountered a problem.
I have a very simple program that tries to create pngs and save them in a user selected folder.
byteimage is a a private byte[]:

byteimage = bcd.createPNG(300, 140, ColorSpace.TYPE_RGB, Color.BLACK, Color.BLACK);

setPath() is called inside the action listener of the browse button

private void setPath() {

    JFileChooser pathchooser = new JFileChooser();
    pathchooser.setMultiSelectionEnabled(false);
    pathchooser.setFileSelectionMode(JFileChooser.DIRECTORIES_ONLY);
    pathchooser.setApproveButtonMnemonic(KeyEvent.VK_ENTER);
    pathchooser.showDialog(this, "OK");

    File f = pathchooser.getSelectedFile();
    if (f != null) {
        filepath = f.getAbsolutePath();
        pathfield.setText(filepath);
      }
}

Byte to png method looks like this:

public void byteToPNG(String filename) {
        try {
        InputStream in = new ByteArrayInputStream(byteimage);
        BufferedImage bufferedimg = ImageIO.read(in);
        ImageIO.write(bufferedimg, "png", new File(filename));
    } catch (IOException e) {
        System.out.println(e.getMessage());
    }
}

This method is called like this:

byteToPNG(pathfield.getText() + System.getProperty("file.separator") + textfield.getText() + ".png");

textfield.getText() sets the actual name of the png.
Inside the constructor, default filepath is set:

filepath = System.getProperty("user.dir");
pathfield.setText(filepath);

The code runs fine from Eclipse and it produces a png image at the desired location.
Unfortunately, after exporting as jar, it starts but when the button for generating the png is pressed, nothing happens. I’m thinking there’s a problem at InputStream or BufferedImage, but I’m a bit puzzled.

Answer 1

If the String fileName passed to byteToPNG isn’t absolute (i.e. written in the form “C:/foo/bar/etc”) that could be the cause of the broken jar. You could also try running the jar file in the terminal using the command:
java -jar myJarFile.jar.
This will cause a console window to remain open alongside your running jar application in which all your applications output (including any exceptions) will be printed.