Updated Jar not Downloaded

Question

For some reason when users launch my program from web start the latest version is not downloaded if the user has an older version in cache.
My JNLP file is:
<?xml version="1.0" encoding="utf-8"?>
<jnlp spec="1.0" codebase="http://slime.tjtech.org/" href="netSlime.jnlp">
   <information>
      <title>Networked Slime Volleyball</title>
      <vendor>Sam Gross</vendor>
      <homepage href="index.html"/>
      <description>Client for Networked version of Slime Volleyball</description>
      <icon href="splash.gif"/>
    </information>
   <resources>
      <j2se version="1.4.*" max-heap-size="256m"/>
      <jar href="GNetGame.jar" main ="true" download="eager"/>
   </resources>
   <security>
      <all-permissions/>
   </security>
   <application-desc main-class="GApplet"/>
</jnlp>I would greatly appreciate your help,
Sam

Answer 1

When not using the version protocol (as is the case when you do not specify a version attribute in your jar resource line), JWS uses the timestamp of the jar as a pseudo version. The JWS client retrieves this using a HEAD HTTP request.
I assume you have tested this situation on your own machine (downloaded the new version while the old version is in your JWS cache)?
If it fails for you as well (and assuming you are able to test without going through a proxy), then it suggests that there are timestamp issues, perhaps your deployment mechanism is somehow always assigning the same timestamp, or the web server is not responding correctly to the HEAD request (which seems unlikely...).
If it works for you, but not some portion of your user community, then investigate whether the affected users are going through a proxy - when using the non-version protocol, the jar URLs do not change between versions, and hence perhaps give poorly configured proxies an opportunity to return a stale version of the jar.
When using the version protocol, the jar HTTP requests have a query string ?version-id=x.x, which one might think reduces the chance that a proxy will misbehave.
At any rate, a possibly worth considering.
HTH