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Web start to actually work.

6 replies [Last post]
Joined: 2004-03-04

My question is whether anyone else has these problems or whether there are easy work arounds to fix them:

I had played around with web start a while back and it seemed a little flakey. I thought that with time the issues would get sorted out.

I've been ignoring it, but now it has become an issue because of work. So what is the current state of the web start art? It is now (late) 2005 and if anything web start has gotten a *lot* worse.

Example: on XP repeatedly install and then uninstall the 1.5 JRE. Watch as it plays havoc with your system! w00t! Fun for the whole family. Especially the part where you have to blow away and reinstall all your other Java versions to try to get back to a working 'stable' system.

Is 1.5 still in beta or what?

Be in shock and awe as over 90% of the webstart links people post online fail to work. (Actually - my result is much closer to 100% failure). NB: for this is actually 100% failure. I cannot recall ever seeing a working webstart link on

Then we get to the 'fun' of different versions of Java. Okay. I understand that your funky new generics enabled uber app requires 1.5 to run. And I'm pretty much okay with that. The problem is that of course they then won't run under 1.4 versions of web start (some of which were otherwise semi-stable).

Why would you want to cut off 50% or more of your potential audience? I'm pretty sure that 1.5 doesn't come installed on most pcs, even the new pcs. But what is worse, is that the opposite seems to be true as well.

We have (for instance) a Web Start app compiled under a 1.3 JDK (don't ask), running on 1.4 web start clients quite happily... but under 1.5 it fails to start.

It makes me curious about what would happen if you used the 1.5 compiler and compiled under compatibility with previous versions mode.... would you then get a web start app which completely failed to open on any version of web start at all???

This is very disappointing. The web start experience is a much lower quality than other aspects of Java.

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Joined: 2004-02-10

> I now have workarounds for a number of the things
> that were bugging me.
> Turns out that my suspicion was correct. 1.5 won't
> run 1.4 classes at all because the class file format
> changes. So much for that.
Do I understand correctly? 1.5 WebStart won't run 1.4 classes?

Joined: 2004-03-04

I now have workarounds for a number of the things that were bugging me.

Turns out that my suspicion was correct. 1.5 won't run 1.4 classes at all because the class file format changes. So much for that.

To solve my intallation woes (webstart not working, manually downloading and running the JREs from Sun not working, web start console crashing and refusing to start (seriously, the list goes on), I fiddled with the J2SE parameter in the jnlp file. When I specified an exact version (ie stripped the + off the end of 1.4.0+)* then webstart would go and grab that version and install it and use it to run the app... yes, even the ones that were crashing if I downloaded them and ran the installer myself. Weird. Looks like you shouldn't install any of the JREs 'by hand'. (_cough_ QA issues _uncough_)

(Excessive sarcasm warning)

* This is of course stupid. _However_ in the defence of whichever anonymous programmer (not me, I could find out from cvs if I cared) put together the jnlp file many many moons ago, from what I can tell this was the recommended practice way back then, since noone believed that sun would be so collossally stupid as to fork the class file format in such a way as to completely break the main compelling advantage of Java: compile once run anywhere.

Bitter? Moi? Ne pas compris mon ami?

Joined: 2004-03-04

Oh yes (sorry about the triple post, bad form old chap and all that)

Instead of:


which will spit the dummy on a 1.5 client.

To get all the official 1.4 Java releases we should have used:


in our J2SE line in the jnlp file.


Joined: 2004-03-04

Webstart started playing up again. (Insisting on downloading and running the installer everytime, even though I already had that version)

This time the fix, interestingly enough, has enabled me to get our app working with the original 1.4 class files under 1.5. I'd be happy if I wasn't so annoyed. >:-(

This time the problem was with our jnlp file, and we used an old way of referring to the main class:

eg us/gov/there/is/no/spoon/I/mean/global/warming

whereas that used to work in 1.4 (well, it mysteriously stopped working for me today, and 1.4 started giving the same complaint as 1.5 about not being able to load the main class file eg:

java.lang.NoClassDefFoundError: Illegal name

There was a 'sharpening' of the implementation so that it conformed to the spec which says that /s in class names are verbotten. So I changed it to:


(apologies to all effected by flooding)

Joined: 2007-03-10

removed spam post - sonya

Message was edited by: sonyabarry

Joined: 2004-01-07

I have to agree here.

Keeping in mind webstart should be the successor of applet solving the stability and robustness problems I am quite dissappointed by it.

Its less robust than applets and to get it completly right is extremly hard. For example I had to play arround two weeks till caching and everything worked as it should. We now transmit all webstart-related content throu the JNLPDownloadServlet.
Why couldn't it be as simple as it was with applets? Do you really think this way you can attrakt developers?

lg Clemens