Java Applet Problems

[Jossy Barron]

I am trying to compile to a JAR the attached files to run in a web browser, i believe i have the HTML code correct, comparing it to others. However i am getting these errors when running it in the webpage:

oad: class MazeApplet.class not found.
java.lang.ClassNotFoundException: MazeApplet.class
at sun.plugin2.applet.Applet2ClassLoader.findClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at sun.plugin2.applet.Plugin2ClassLoader.loadCode(Unknown Source)
at sun.plugin2.applet.Plugin2Manager.createApplet(Unknown Source)
at sun.plugin2.applet.Plugin2Manager$AppletExecutionRunnable.run
(Unknown Source)
at java.lang.Thread.run(Unknown Source)
Caused by: java.io.FileNotFoundException: Z:\Documents\Uni Work
\09.10\Advanced Web Games Development\Week 2\MazeApplet\class.class
(The system cannot find the path specified)
at java.io.FileInputStream.open(Native Method)
at java.io.FileInputStream.(Unknown Source)
at java.io.FileInputStream.(Unknown Source)
at sun.net.www.protocol.file.FileURLConnection.connect(Unknown Source)
at sun.net.www.protocol.file.FileURLConnection.getInputStream(Unknown
Source)
at sun.plugin2.applet.Applet2ClassLoader.getBytes(Unknown Source)
at sun.plugin2.applet.Applet2ClassLoader.access$000(Unknown Source)
at sun.plugin2.applet.Applet2ClassLoader$1.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
... 7 more
Exception: java.lang.ClassNotFoundException: MazeApplet.class
MazeApplet::init() called
java.security.AccessControlException: access denied
(java.io.FilePermission wall.png read)
at java.security.AccessControlContext.checkPermission(Unknown Source)
at java.security.AccessController.checkPermission(Unknown Source)
at java.lang.SecurityManager.checkPermission(Unknown Source)
at java.lang.SecurityManager.checkRead(Unknown Source)
at sun.awt.SunToolkit.getImageFromHash(Unknown Source)
at sun.awt.SunToolkit.getImage(Unknown Source)
at javax.swing.ImageIcon.(Unknown Source)
at javax.swing.ImageIcon.(Unknown Source)
at MazeApplet.init(MazeApplet.java:91)
at sun.plugin2.applet.Plugin2Manager$AppletExecutionRunnable.run
(Unknown Source)
at java.lang.Thread.run(Unknown Source)
Exception: java.security.AccessControlException: access denied
(java.io.FilePermission wall.png read)
MazeApplet::start() called
MazeApplet::run() called

Can anyone shed any light onto why the file does not run, attached is a zip of the source and some additional files needed for the class

Cheers
Jossy

AWGD_Maze.zip

[Kalakian]

That should be the game engine now fixed as well, which is handy since I'll be introducing it tomorrow. Thanks for highlighting that error before anybody started using it :)

The sorted function in the game engine is:

static public Image loadImage(String filename)
{
Toolkit tool = Toolkit.getDefaultToolkit();
URL url = GameApplet.getInstance().getClass().getResource(filename);
Image img = tool.getImage(url);
MediaTracker mTracker = new MediaTracker(GameApplet.getInstance());
mTracker.addImage(img,1);
try
{
mTracker.waitForID(1);
}
catch (InterruptedException e)
{
e.printStackTrace();
}

return img;
}

But when passing a path, you must make sure to preceed it with a forward slash '/' so it knows to look for the image relative to the root of the jar, which is important if your code is split into packages. That's why it wasn't working for the engine at first, because it was looking for the image relative to the current class file inside a package structure.

So the code you need to allow images to be loaded from inside the jar file, whether using packages or not would be:

tool.getImage(getClass().getResource("/wall.png"));

[Jossy Barron]

and thats it :) well done deryk

[Kalakian]

Ok, I think I've found the source of your problem, and it appears the same problem exists in the game engine. Typical, I have created jar files with sprite loading, tested them, and everything is fine, but when I implemented image loading in the game engine I have only tested it from inside eclipse :/

Quick fix for you should be to use

tool.getImage(getClass().getResource("wall.png"));
instead of
tool.getImage("wall.png");

which basically looks for the png file relative to the class file (i.e. inside the jar). I'll need to fix the game engine as this doesn't actually work because it looks for resources relative to the game engine class files rather than the game code class files. That's my problem though, let me know if your applet now works.

[Jossy Barron]

yey, new set of issues, seems to be recognising the class file now, what would cause this error?:

Reading certificates from 11 http://jossyb2000.googlepages.com/AWGDMaze.jar | C:\Documents and Settings\B00105397\Application Data\Sun\Java\Deployment\cache\6.0\45\1069fc6d-16d22ca9.idx
MazeApplet::init() called
java.security.AccessControlException: access denied (java.io.FilePermission wall.png read)
at java.security.AccessControlContext.checkPermission(Unknown Source)
at java.security.AccessController.checkPermission(Unknown Source)
at java.lang.SecurityManager.checkPermission(Unknown Source)
at java.lang.SecurityManager.checkRead(Unknown Source)
at sun.awt.SunToolkit.getImageFromHash(Unknown Source)
at sun.awt.SunToolkit.getImage(Unknown Source)
at MazeApplet.init(MazeApplet.java:92)
at sun.plugin2.applet.Plugin2Manager$AppletExecutionRunnable.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)
Exception: java.security.AccessControlException: access denied (java.io.FilePermission wall.png read)
MazeApplet::start() called
MazeApplet::run() called

most recent JAR file attached - not protected
AWGDMaze.jar

[Ross Forshaw]

The method I posted above does not require the images to be stored in the .jar file. Though when passing file paths to it, it is best to make them relative.

[Jossy Barron]

right i think i know what one of the problems is but dont know how t fix it, i changed the image method over so that should be fine, reading up online it seems that eclipse doesnt export all the libs u need or rather running within eclipse is fine but without it needs addditional libs added, i jus dont know how to do that.

I google part of this error and discovered this:

Projects must be referenced by an EAR or a WAR to use classpath publish/export dependencies whose runtime path (../) maps into the parent component.

any ideas?

[Kalakian]

Ah, but have you uploaded the class files for your game or is it packaged in a jar file? That's the method he was already using and was getting an error for.

[Ross Forshaw]

This setup is guaranteed to work on the Internet as I used it for my Asteroid game.

import java.awt.* ;
import java.awt.geom.* ;
import java.awt.event.* ;
import java.net.* ;

public class Sprite()
{
Image img ;
Sprite( String path )
{
java.net.URL imageURL = Main.class.getResource( path ) ;
this.img = new javax.swing.ImageIcon( imageURL ).getImage() ;
}
}

And that is pretty much it when it comes to loading Images for Web games. :)

[Jossy Barron]

thanks :)

[Kalakian]

Just noticed you had attached your source code, and you are using the swing method of loading images. Try the method I posted above and you should be fine.