Does the Browser cach the jnlp-file?

Question

I have a problem, I think with the browser's caching. As I modify the *.jnlp-File, the old version is loaded, not the new one!
Or is the old version cached by the webStart-Caching-Mechanism?
To update the jnlp-file, sometimes it is helpful to clear the Clients webStart cache.
Is that correct?
regards,
ulli

Answer 1

The browser does in fact cache the jnlp and it can be a real problem. If there is no expiration on the JNLP then the browser may load it from cache instead of going to your web server on the next access. This means you may have modified your JNLP on the server for a new release, but users can start your application WITHOUT GETTING THE LATEST JNLP!
You can solve this problem by serving the JNLP file from your own servlet (or other HTTP serving technique) and setting the expire header. Setting it to 0 does the right thing.
Do NOT however, set "Pragma", "no-cache". no-cache stops the browser from writing the JNLP to the file system...this in turn causes a problem when Web Start tries to find the jnlp file after the browser starts Web Start....the jnlp file is not there.
Note that the JnlpDowloadServlet provided by Sun in the Web Start developers kit does NOT expire the JNLP file...you must fix this code yourself if you want it to work correcly. Sun was supposed to make this source code available but I can't find it anywhere. We used a de-compiler to de-compile the code, fix it and re-jar it.