Loading files (images) from a JAR

Newbie & Debugging Questions
#1

Okay, here goes:

I’m trying to load two images from a .jar file that contains two folders (and the META-INF, but that doesn’t matter in this situation), volatileimagetest (where the code is) and images (where the two images are).
When I run the code (below) before it’s packaged into a .jar, it runs just fine. I have two directories, volatileimagetest (where the code is) and images (where the two images are). The directories are exactly the same as in the .jar, but not in a jar file.

Now I saw on http://weblogs.java.net/blog/chet/archive/2004/08/toolkitbuffered.html that to load images from within a .jar file, I should use the code (slightly modified of course):

URL url = getClass().getResource("/images/img1.png");
BufferedImage img = ImageIO.read(url);

This loads the images when running outside the .jar file. I printed url to System.out, and got this: “file:/C:/Documents%20and%20Settings/Owner/My%20Documents/Java/VolatileImage/build/classes/images/img1.png”. I feel I should just say the directory volatileimagetest is located in the same directory as images, and contains all class files.

When I run this as a .jar, I get a NullPointException, and I narrowed it down to the line “URL url = getClass().getResource(”/images/img1.png");", with getResource() returning null.

Has anyone experienced this, and if so could they please help ???

#2

Can you do me a favor? Type "jar -tvf " on the command line and paste the output here. I’d like to see precisely how the JAR is organized. Also, what package is the main class in?

#3

I got:

 0 Tue Jan 10 21:07:06 GMT-07:00 2006 META-INF/

202 Tue Jan 10 21:07:04 GMT-07:00 2006 META-INF/MANIFEST.MF
0 Tue Jan 10 20:43:00 GMT-07:00 2006 images/
0 Tue Jan 10 20:43:00 GMT-07:00 2006 volatileimagetest/
78425 Mon Jan 09 17:05:24 GMT-07:00 2006 images/img1.PNG
238 Mon Jan 09 17:06:06 GMT-07:00 2006 images/img2.PNG
4717 Tue Jan 10 21:07:06 GMT-07:00 2006 volatileimagetest/Form.class
771 Tue Jan 10 21:07:06 GMT-07:00 2006 volatileimagetest/Main.class

#4

Well, “PNG” != “png”.

Always use lowercase extensions.

#5

looks like you are using Windows which is not case sensitive… or maybe a mac… but java is generally case sensitive.

#6

Well, the filesystem is case insensitive on windows (sorta), but jars certainly aren’t (because the OS isn’t involved in the resolving process).

#7

is have another etra question
lets say is hava a main jar
in which i have an images.jar which contains all my images
how can i load those?

#8

No, you dont pack jars inside jars. (That doesnt make any sense)

Well, anyways… you could load a jar inside a jar inside a jar inside a jar… with some ZipInputStream or a JarInputStream, but it doesnt make any sense… mind you.

#9

to keep it cleen?
was just a question anyway

#10

I usually do. Must have been a fluke with the image editing/creation program I was using (it defaults to upper. I usually remember to change it to lower). Thanks for pointing that out. I am running Windows, so I’m used to case-insensitivity. I’ll try changing that when I get to my compiler (at school right now…).

#11

to keep it cleen?

Well, you can either use several jars for different parts (nice for webstart). Or if it needs to be a single jar you can just use directories (inside the jar).