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MQSeries.net Forum Index » WebSphere Message Broker (ACE) Support » Singeltons created in Java Plugin not accessible to JCN

Singeltons created in Java Plugin not accessible to JCN

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jcraw62

Posted: Wed Jul 11, 2007 10:17 am Post subject: Singeltons created in Java Plugin not accessible to JCN

Newbie

Joined: 17 Mar 2006
Posts: 6

I am instantiating a singelton in the contructor of a Java plug-in. The plug-in appears to load OK but when I attempt to retreive the instance in a JCN it is not loaded.

Is this because plugins and JCNs use different classloaders ? Ideas on how I can get around this ?

Many thanks.

Posted: Thu Jul 12, 2007 12:57 am Post subject:

Apprentice

Joined: 07 Aug 2006
Posts: 48
Location: England

My exprience with the JCN is that only try to implement your user code within the evaluate method. JCN Contructors are called when you are deploying bar files to execution groups and this might not be the time you really start executing that code.

Singleton pattern - allows you to initiate it once and at the time when you first need to use it. So if your sigleton class has a static method to return this instance i.e.

static Singleton Instance(){
if (_instance == null)
_instance = new Singleton();
return _instance;
}

This means that you can now concentrate on using/calling the static method Instance().anyMethod() within the evaluate of the JCN. Do all your initialisation within the Singleton constructor if possible.

jefflowrey

Posted: Thu Jul 12, 2007 7:07 pm Post subject:

Grand Poobah

Joined: 16 Oct 2002
Posts: 19981

Yes, JCNs and plugins use different classloaders.

Put your singleton class into a jar file that is put into shared-classes.
_________________
I am *not* the model of the modern major general.

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