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Singleton Pattern

Balaji Nagarajan

Joined: Jul 15, 2002
Posts: 4
How do i implement a Singleton in a J2EE application(for server side classes)?
Lasse Koskela

Joined: Jan 23, 2002
Posts: 11962
This is a common question to which there is no standard answer as far as I know. The problem is that the application may reside in a clustered environment made of several JVMs.
Here are some resources related to the subject:
J2EE Singleton pattern at
JBoss clustering / singleton services
J2EE singleton by

Author of Test Driven (2007) and Effective Unit Testing (2013) [Blog] [HowToAskQuestionsOnJavaRanch]
Gustavo Adolpho Bonesso
Ranch Hand

Joined: May 11, 2002
Posts: 103
I agree with Lasse, but if you are in a enviroment with a single JVM, the Singleton Pattern is usefull to make DAO�s (Data Access Objects).

Gustavo Adolpho Bonesso<br />SCJP1.4
I agree. Here's the link:
subject: Singleton Pattern
jQuery in Action, 3rd edition