Google站点中的Java小程序和“不兼容的幻数”错误

Question

I've seen many questions around this topic, but not one which answered my specific situation. I've finished writing a Java applet that I want to embed on a Google Sites website. I have packed the entire applet in a single .jar file, uploaded it as a general Attachment to the site, and used the CodeWrapper widget to link it into the page, by inserting the proper values for codebase and archive (basically, I picked the download link for the attachment and split it in two: the path for the "codebase", and the file name for the "archive"). However, I get a:

Incompatible magic value 1008813135 in class file *my class file*

error when trying to run it. It seems like this number corresponds to ASCII <!DO , thus making many think that it actually stands for the beginning of a XML document, and that this is a 404: file not found error that I'm getting. I thought this might be related to the structure of Google Sites, and tried uploading the .jar file on my Public Dropbox folder. In fact, by performing the same operation as said above (splitting path and filename between "codebase" and "archive") it works perfectly well! So I am sure that the problem really is Google Sites. For now I will make use of the Dropbox solution, but it's not really something I want to rely on; I'd feel much better if I could just embed the file inside the site. Does anyone have any suggestions with regard to this?

Answer 1

Hosting .jar files on Google Sites results in a caching effect with googlegroups.com. I can't say right now why this is, but you can see evidence of it in the Java console if you set the tracing level to 5.

For some applets I have, this poses no problem. However, I encountered security exceptions with getSoundClip that I couldn't figure out in my applet. It always worked when I hosted it on a site set up by my ISP. I noticed the odd googlegroups.com URLs coming from some kind of cache, appearing in the console. Default console settings don't show caching, if I'm not mistaken.

Uploading the .jar file to code.google.com (and setting codebase, etc.) doesn't have any caching (that I can see) and my getSoundClip calls work with no security exceptions.

In the following extract from the console of an applet that works for me on Google Sites, you can see an example of a URL on sites.google.com and its corresponding cache in bab6424e-a-62cb3a1a-s-sites.googlegroups.com . Note: I replaced the true path in the URLs with X/Y and the jarfile with Z.jar

...
basic: Added progress listener: sun.plugin.util.ProgressMonitorAdapter@bc71bd
basic: Plugin2ClassLoader.addURL parent called for https://sites.google.com/site/X/Y/Z.jar
security: Accessing keys and certificate in Mozilla user profile: null
security: JSS is not configured
security: Blacklist revocation check is enabled
security: Trusted libraries list check is enabled
cache: Adding MemoryCache entry: https://bab6424e-a-62cb3a1a-s-sites.googlegroups.com/site/X/Y/Z.jar?attachauth=ANoY7cpwDuO2zcBBImZ-rJvrPReeiY0EyL874NTY538mtqnsfd-A6p4uVsSKbeO0jcW336bRzkmqoJSiKk3MgG6dxISu6iXodhaXlmyxEaZ2sZ8sSkEkABSMu89vHzugUVfF2m31qp3N5RFe5QSqVMoY2vMjf7HAjLVmObNEmp7J83khcV1jepHpudfPZXhYeXD89Bv6XbBaePhwoueUZT9ZPEwNvepaKwGIr2IsActrdYOtrjiRScAzyp2dr9EwhnZXXIv6KsKv&attredirects=0
network: Cache entry found [url: https://sites.google.com/site/X/Y/Z.jar, version: null] prevalidated=false/0
cache: Adding MemoryCache entry: https://sites.google.com/site/X/Y/Z.jar
...