Java unknown source with ImageIO

Question

My program runs fine in Netbeans, but I get the following error when I run my applet in a browser:

java.lang.IllegalArgumentException: input == null!
    at javax.imageio.ImageIO.read(Unknown Source)

I opened the jar to verify that the png files are correctly placed there. I'm not certain why the following doesn't work (in a try block, of course):

BufferedImage beam = ImageIO.read(this.getClass().getResource("images/beam.png"));

I've tried other things like the following, but suspect the problem might be something else.

URL url = this.getClass().getResource("images/beam.png");
BufferedImage beam = ImageIO.read(url.openStream());

Your advice is appreciated.

`URL url = this.getClass().getResource("images/beam.png");` The image is in a sub-directory of the package of the calling class? To make that path from the root of the class-path, make it `URL url = this.getClass().getResource("/images/beam.png");` And be sure to print out the URL or inspect it in a debugger. It seems like you are running on guesses at the moment. — Andrew Thompson, Oct 11 '12 at 14:25
Can you explain how you've structured your JAR file where the class and images are placed? Might help trigger some ideas. — jheddings, Oct 11 '12 at 14:32
myJar.jar is in the same directory as lib. The jar has directories mypackage and META-INF. The mypackage directory has the class files and the directory images. The images directory has the png files. I think the path "images/beam.png" is relative to the class files. — Paul Lombardi, Oct 11 '12 at 15:02
Sorry that my responses are delayed. I'm working on this with people coming in and out of my office. — Paul Lombardi, Oct 11 '12 at 15:40
*"I think the path "images/beam.png" is relative to the class files."* Our thinking aligns, but to make that path explicit use `/mypackage/images/beam.png` as the path string. — Andrew Thompson, Oct 12 '12 at 05:31

Gilberto Torrezan · Accepted Answer · 2012-10-11T14:34:36.213

1

The problem is in your path String. Use this instead:

BufferedImage beam = ImageIO.read(this.getClass().getResource("/images/beam.png"));

(Note the / before the path)

edited Oct 11 '12 at 14:34

answered Oct 11 '12 at 14:26

Gilberto Torrezan

5,113
4
31
50

Changing the path to "/images/beam.png" does not fix the problem. – Paul Lombardi Oct 11 '12 at 15:04
So where is your `beam.png` file in your JAR? You have to use the full path. – Gilberto Torrezan Oct 11 '12 at 15:25
For NetBeans to build a jar that works in a browser, the images directory must be in the src directory and not the package directory, and then the "/" before the path works: "/images/beam.png". – Paul Lombardi Oct 15 '12 at 22:13

score 0 · Answer 2 · answered Apr 19 '19 at 21:31

For the record and If someone is stucked with this type of error for some reason eclipse auto changed the build path and blocked the image path from being packaged.

To change this setting just right click on the project name -> Properties-> Java Build Path-> Source Tab and check that the folder containing the images is not excluded, if it is just remove that rule.

Java unknown source with ImageIO

2 Answers2

Linked