Exporting to jar error

[Sean2012]

Hi, i'm trying to export my eclipse project to a jar. I export it and everything is fine but when i go to run it i get this error.

C:\Documents and Settings\Administrator\Desktop>java -jar game.jar
Running...
Check Texures!
Exception in thread "Thread-3" java.lang.ExceptionInInitializerError
        at com.war.warfare.graphics.Render3D.floor(Render3D.java:58)
        at com.war.warfare.graphics.Screen.render(Screen.java:27)
        at com.war.warfare.Display.render(Display.java:137)
        at com.war.warfare.Display.run(Display.java:107)
        at java.lang.Thread.run(Unknown Source)
Caused by: java.lang.RuntimeException: java.lang.IllegalArgumentException: input
 == null!
        at com.war.warfare.graphics.Texture.loadBitmap(Texture.java:19)
        at com.war.warfare.graphics.Texture.<clinit>(Texture.java:8)
        ... 5 more
Caused by: java.lang.IllegalArgumentException: input == null!
        at javax.imageio.ImageIO.read(Unknown Source)
        at com.war.warfare.graphics.Texture.loadBitmap(Texture.java:11)
        ... 6 more

I'm new to java and can't find out what is wrong. I also uploaded my project files.
Thanks for any help!

game.zip

[pbrockway2]

Caused by: java.lang.IllegalArgumentException: input == null!
        at javax.imageio.ImageIO.read(Unknown Source)
        at com.war.warfare.graphics.Texture.loadBitmap(Texture.java:11)

Evidently the read() method was passed null in the statement on line 11 of Texture.java.

public static Render loadBitmap(String fileName) {
    try {
        BufferedImage image = ImageIO.read(Texture.class.getResource(fileName)); // <-- line 11
        int width = image.getWidth();
        int height = image.getHeight();
        Render result = new Render(width, height);
        image.getRGB(0, 0, width, height, result.pixels, 0, width);
        return result;
    } catch (Exception e) {
        System.out.println("Check Texures!");
        throw new RuntimeException(e);
    }
}

If you stop and think about it filename might have represented the name of a file on your harddisk somewhere, but that is no good now that your image textures are entries within a jar archive file.

The thing to do is to use the form of the read() method that takes a URL argument. There is a method of the Class class - getResource() - that is useful in constructing this URL at runtime. Its use (and comparison with the similar CLassLoader method) is discussed in this JavaWorld article.

As you move from file to URL based access of resources one gotcha (if you're on Windows) is with the case of the names. If you are trying to access "Floor.png" and your program happens to use the string "floor.png" then nothing will go wrong so long as you are dealing with files and Windows. But the moment you put things into a jar archive the rules change: names are case sensitive and the resource won't be found. A rule like always using lowercase for resources will help avoid this trap.

[Sean2012]

Yes, I eventually figured it out on my own, but thanks for the reply! I learned a lot from it! I'm new to all this and this is my first jar file. Thanks!

[pbrockway2]

Glad to hear you've figured it out. You're welcome, and good luck with the game.