[HELP] Java Context Class Loader Exmaple / Setup

[sjunejo]

Hi,

I am in process of developing a Java application (war) which will be deployed in an Application Server like jBoss, WebSphere, WebLogic and Glassfish. Within my code I am getting an instance of a class which is 'static', now If I deploy two instances of the same application, both will end up using same static instance rather than different. Is there anyway I can have only one instance of a class for each separately deployed application without using 'static' property. I heard about this 'Context Classloading Stuff' but couldn't grasp the idea. Can anyone explain or refer me to the good article about it. Also, I am looking for an example, seems like its all about configuration of my application at deployment time but how?

I am quite new to java so please accept my apology if I am talking nonsense.

Thanks,

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SJunejo

[Norm]

If I deploy two instances of the same application, both will end up using same static instance rather than different

What do you mean by "deploy" an instance?
Are you loading all of the classes for an application in the same JVM?

[sjunejo]

I mean copy of the same application with different settings....I think jBoss load's all *.war in single Web Container?

[Norm]

copy of the same application with different settings

Are you talking about disk files copied into another disk file (like a jar)
or about the bytes of a class file loaded into the jvm where they can be executed.

What is it that is "copied"? And where is it copied to?

[sjunejo]

OK....I think there is something I have missed. Let me explain, I have an application called ABCLive.war and ABCTest.war (both files copies of each other) and configured to use some resources from Application Server. ABCLive.war is configured to use 'jca/abcConnectionFactoryLive' and ABCTest.war is configured to use 'jca/abcConnectionFactoryTest' resources present in an application server. As I mentioned earlier both of the applications have same classes, same servlet and everything but uses different bindings in application server deployment descriptor i.e jboss-web.xml.

The class which is responsible to perform lookup to these resources within my application is called 'ServiceLocater' which is implemented as 'singleton' instance. If I start using my 'ABCTest' application it will work OK and uses correct cx-factory i.e. 'jca/abcConnectionFactoryTest' without any problem, but now if I try to use ABCLive deployment it will end up using same jca resource as Test deployment instead of using 'jca/abcConnectionFactoryLive'.

I found out that jboss will load both apps in the same web container and because of that both instances are end-up using single instance of ServiceLocater. Now what I want to know is that is there anyway I can achieve this singleton pattern without making it static.

Hope this makes a bit more sense.

[Norm]

The singleton needs a place to keep a reference to the single instance it defines.
A static is one way. Perhaps there are other places to keep the single reference.

[Norm]

Here's an idea:
If you want a different version of the singleton class for each "environment", use a static Map to hold the reference to the class instance for each environment.
No idea how to detect which environment the singleton is in.