Applet freezes while Jar is loading

Question

Hi everyone,
I have a fundamental question concerning the loading mechanism of an applets resources.
The problem is as follows:
I have two jars, the first containing all *.class files, the second (size: 10MB) containing only graphics and sounds.
I start the applet with this code:
<APPLET ARCHIVE="init.jar,resources.jar" HEIGHT="100" [...]>Of course the point is to have the small init.jar loaded fast an display a loading animation while the big file is beeing loaded in the background. Up to here everything works as expected. When i start the applet, the init.jar is loaded and displays a loading animation as long as i try to get a resource from the resource.jar.
When I do that, my applet freezes while the big resource.jar file is beeing downloaded.
This is how i access the resource in the resource.jar
public void run() {
     while(/*some condition*/) {
          // this is the line which blocks until whole jar is downloaded
          java.io.InputStream input = this.getClass().getClassLoader().getResourceAsStream(/*resource String*/);
          // use input to load resource
}The freeze happens only upon the first time the while-loop runs, after that the resource.jar is chached and access is almost instant.
Now the concrete problem is, that the applet freezed in all its threads while the jar is beeing downloaded. I NEED to display an idle animation while this is done.
Has anyone any suggestion how i can avoid the complete freeze?
I have already concidered to load the resources without specifing the jar in the HTML-ARCHIVE-Tag, this works becouse of the codebase i can load the ressources from, but the problem is, that these resources have a large overhead from the server to the client until i can use them in the program.
Also it is no option to load them all on startup in another backgound thread (which would slove the freeze problem, i tried it), becouse i have to dynamically load and unload these resources to avoid OutOfMemory-Errors. Reloading them brings the overhead-Problem up again.
Only when i specify the 2nd jar in the ARCHIEVE-Tag i have direct access to the browsers chache without wasting memory when holding references to all resources.
After all every loading and stuff works, there are no errors in the programm only this strange behaviour. I Also tried it with different VMs, on different OS, and different Browser, all the same.
I would be glad if someone could give me a hint on this, i've been searching for days now, even tried to analyse the Classoader sources but ended up in sun's native calls...
Thank you in advance
- Loddi

Answer 1

I've been encountering the same problem and I think I've figured out the reason behind it and how to solve it.
It appears that the class loader can only ever load one resource at a time. Once you've forced it to start downloading resources.jar, it can't load any classes until that download has finished, not even classes that are part of the Java API. In your case I believe the solution would be to display one loop of your idle animation before you start loading resources.jar, to make sure that everything the idle animation needs has already been loaded by the class loader.