Extension mechanism

Question

I have developed an applet which uses some utility classes bundled in a jar file. I didn't want the user however to have to download the utility classes in the jar file every time he wanted to use the applet so I thought of making it an optional package. Thus I used the extension mechanism so that the first time the user downloaded the applet he could install the utility jar file as an extension.
The problem that occured is this: From a utility class I load some images to display on the applet. The images reside within the utility jar file so I use the following code to load them:
1:     URL url = this.getClass().getResource(imageName);
2:     ImageIcon imageIcon = new ImageIcon(url);
When I didn't use the extension mechanism there was no problem!
When I did use extensions though a Null Pointer Exception was thrown
at line 2. Obviously the url is null.
This seems pretty strange to me because the image is loaded from within the jar file and the jar file has been downloaded (and installed). So what is the problem?
Any help would be appreciated.

Answer 1

You are using a JVM that supports the extension
mechanism, I hope? Not the Microsoft JVM that comes
with Internet Explorer, for example? If so, then
perhaps you don't know where the extensions directory
really is. The system property "java.ext.dirs" (I
think) will tell you where it really is.
Having gone through this, you may want to rethink your
original idea that it would be more convenient for the
user to download and install the jar file. If you had
this much trouble, how easy would it be for somebody
else?Hey there,
Wonder if you could help me sort something out while you're at it. In my older WIN95 OS I put my extension .jar files - if I remember right - in, say, C:\jdk1.3.1_03\jre\lib
. . . and things worked fine.
I just upgraded to XP and I added my extensions to both C:\jdk1.3.1_03\jre\lib & C:\Program Files\JavaSoft\JRE\1.3.1_03\lib\ext
. . . It finds the files fine, but my .jar files - that have in them some of the same files as in my extension .jar - are faultering. I'm trying to figure out if I need to add the CLASSPATH to my SYSTEM | ENVIRONMENTAL variable, or to my .jar applications. You have any ideas?
Thanks in advance;
~Bill