Re: Singleton behaviour

[Magne Skjeret]

Shapira, Yoav wrote:
Hi,
JBoss (some versions thereof, or some configurations, at least) use a
Unified Class Loader where the classloader is shared among webapps.
Your understanding that each webapp should have its own classloader (and
does, in tomcat) is correct.  Further, your understanding that the two
singletons would be separate, once per context classloader, is also
true.  Is the base class shared (in common/lib or another shared
location) or duplicated (one copy in each WEB-INF/lib)?
 

Ah good to know. I was starting to doubt myself and saw myself doing 
university all over again. :-)
The jar files are duplicated. One in each WEB-INF/lib.

I found in the jboss-service.xml inside the tomcat sar that it does seem 
to use the unified classloader.
<attribute name="*UseJBossWebLoader*">true</attribute>

A bit out of the scope of this list, but is there any know complications 
using tomcats classloader instead?

Magne
Yoav Shapira
Millennium Research Informatics
 

-----Original Message-----
From: Magne Skjeret [mailto:[EMAIL PROTECTED]
Sent: Friday, June 04, 2004 2:28 PM
To: Tomcat Users List
Subject: Singleton behaviour
Hi
I had a peculiar experience today, which really conflicts with my
previous knowledge.
I have 2 applications that use the same base classes (just UI
   

differences).
 

I have duplicated those jar files into each of the contexts
   

WEB-INF/lib.
 

I try to start a singleton in each of the contexts: e.g
WebProperties.getInstance()
But it only seem to do it once, so the singleton is shared cross
   

context.
 

I always thought that a static variable was only visible in its
classloader and its children.
Surely each context must have its own classloader??
Is this the expected behaviour?
It is a tomcat that runs inside jboss. tomcat 4.1.29
Could it be a jboss issue? I think I saw something in a config file
about using a jboss classloader.
Thanks
Magne
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