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From Paul Smith <psm...@apache.org>
Subject RE: JMSReceiver - chainsaw (webstart)
Date Thu, 10 Jun 2004 22:25:54 GMT

On Thu, 10 Jun 2004, Stephen Pain wrote:

> Hi Paul,
> Noticed your commit fixing the receiver restart issue... thanks for that.  Did you get
a chance to check out why the duplicate receivers are being shown in the receiver panel again?

I have not been able to reproduce the the duplicate receivers issue yet (I 
did a while ago when I 'fixed' it, but haven't found a condition where it 
appears for me).

> Unfortunately JMS isn't going so well - I've messed around with adding weblogic.jar to
the classpath, no luck.  To run it in eclipse, I have to specify the jar on the classpath
defined within eclipse (in the Run settings); putting it on the system classpath doesn't seem
to help.


> I can run it from ant with the file on the system classpath, but that's to be expected.

It sounds like the weblogic.jar is relying or some other class.  If 
weblogic.jar is handled by the System Class loader, it only has access 
itself and the Bootstrap classloader to find any other class it needs, 
which could be why it's dying, but I thought we would have got a 
NoClassDefFoundError or something rather than a NPE.  Maybe weblogic is 
swallowing a exception somewhere and we see the effects of it in the NPE.

Hence why it works when you have the weblogic.jar file on a more 'normal' 
Classloader.  (Please, I am no Classloader expert, anyone with good 
expereience in this area, please help).

It looks like, for Web start reasons only, that we'll need to have a 
Custom class loader that load Jars from a local machine.  The class loader 
that web start uses will only be able to access the jars from the remote 
server where they were delivered from. It's not practical (or legal 
probably) to have the weblogic.jar on the Apache server.  It would need to 
be Signed anyway.

It's easy to create a Class loader that could load all the jars in the 
.chainsaw/plugins directory.  That is trivial.  The issue is that I 
suspect the Web start Security manager will intercept somewhere and go 
"Wait a minute, this classloader is trying to load an unsigned jar" and 
die with a NaughtyNaughtyError or something.

They only option I can think of is to try.  Given that the Web start 
version has a Java Policy that asks if it can do basically anythin 
(specified in the .jnlp file), I am going to cross my fingers that it's 

The WORST case I can see is going ahead with this custom class loader, and 
_requiring_ YOU to sign the weblogic.jar file.  That could be a way of 
handing the responsibility of verifying the jar I guess.  It's not a bad 
idea, it's just a bit more work for you the user, which is unfortunate.

Stephen, would you be able to help me and provide me with an Unsigned 
weblogic.jar file? (only if it doesn't violate any license stuff)  That 
way I can test it. You can contact me offline if you wish.

Thank you for your patience.  I really want Chainsaw to be as functional 
in Webstart as it is in Ant or Eclipse.

Paul Smith

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