• Post Reply Bookmark Topic Watch Topic
  • New Topic
programming forums Java Mobile Certification Databases Caching Books Engineering Micro Controllers OS Languages Paradigms IDEs Build Tools Frameworks Application Servers Open Source This Site Careers Other all forums
this forum made possible by our volunteer staff, including ...
Marshals:
  • Campbell Ritchie
  • Paul Clapham
  • Ron McLeod
  • Bear Bibeault
  • Liutauras Vilda
Sheriffs:
  • Jeanne Boyarsky
  • Tim Cooke
  • Junilu Lacar
Saloon Keepers:
  • Tim Moores
  • Tim Holloway
  • Stephan van Hulst
  • Jj Roberts
  • Carey Brown
Bartenders:
  • salvin francis
  • Frits Walraven
  • Piet Souris

Question on Singleton Session Bean Initialization

 
Ranch Hand
Posts: 634
Eclipse IDE Chrome Java
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator

Source: EJB 3.1 Spec.



4.8 Singleton Session Beans

A Singleton session bean is a session bean component that is instantiated once per application. In cases
where the container is distributed over many virtual machines, each application will have one bean
instance of the Singleton for each JVM.



Thus,Each Application has only one instance of Singleton Bean.


4.8.1 Singleton Initialization
In some cases, explicit initialization ordering dependencies exist between multiple Singleton compo-
nents in an application. The DependsOn annotation is used to express these dependencies. A
DependsOn dependency is used in cases where one Singleton must initialize before one or more other
Singletons. The container ensures that all Singleton beans with which a Singleton has a DependsOn
relationship have been initialized before PostConstruct is called.



However,from the above paragraph I understand that "there can be multiple Singleton's".

"The container ensures that all Singleton beans with which a Singleton has a DependsOn relationship have been initialized"

Q1. How is this possible as the topic 4.8 says that "Each Application has only one instance of Singleton Bean." ?

Please advise.
 
Creator of Enthuware JWS+ V6
Posts: 3364
305
Android Eclipse IDE Chrome
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator

Q1. How is this possible as the topic 4.8 says that "Each Application has only one instance of Singleton Bean." ?


Each Application has only one instance of Singleton Bean of a certain class. There can be many Singletons in an application.

Regards,
Frits
 
Mohit G Gupta
Ranch Hand
Posts: 634
Eclipse IDE Chrome Java
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
Thanks Frits.
I understood the statement now.
 
reply
    Bookmark Topic Watch Topic
  • New Topic