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singleton class across

guru prasanth
Ranch Hand

Joined: Aug 20, 2009
Posts: 96
Hi,'
I have a singleton class which is referred in a jar file.Now the jar file is included in multiple ear file.Let's take an example.
I have singleton class which is present in a singleton.jar and this jar file is copied in 4 different ear/war file.Now my requirement is
this class has to be singleton across multiple appliation.But when iam instatiating across application(.ear) file then it creates a different
singleton class.Is there any otherway other than making these ear files referring to single jar file.
Andrew Monkhouse
author and jackaroo
Marshal Commander

Joined: Mar 28, 2003
Posts: 11476
    
  94

This doesn't seem to be related to SCEA. Did you mean to post it in BEA/WebLogic? (just guessing based on some of your previous posts). I can move this if you provide a hint on where you would like it moved to.


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Deepak Bala
Bartender

Joined: Feb 24, 2006
Posts: 6661
    
    5

You have these options

1. Move the jar up the class loader hierarchy so that it is loaded once.
2. Use an app server that uses a unified classloader factory. This way the first instance of the class will be picked up and the rest will be discarded.

Any reason why this Singleton is creating a problem across multiple apps ?


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srivastava ashish
Greenhorn

Joined: Apr 12, 2010
Posts: 28
Is your singleton getInstance() method synchronized??

Refer to Head First Design Patterns -pg 180 ...I think you will get your answer.

Ashish
Deepak Bala
Bartender

Joined: Feb 24, 2006
Posts: 6661
    
    5

srivastava ashish wrote:Is your singleton getInstance() method synchronized??

Refer to Head First Design Patterns -pg 180 ...I think you will get your answer.

Ashish


That will not solve the problem when the same class is loaded by different class loaders
srivastava ashish
Greenhorn

Joined: Apr 12, 2010
Posts: 28
Thanks for pointing that out deepak..but is there any harm in putting singleton.jar in server classpath rather than individual EARs??. It might just work
 
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