How do I write a J2EE/EJB Singleton?


walkur
HOME ยป Programming Languages

A day ago my application was one EAR, containing one WAR, one EJB JAR, and a couple of utility JAR files. I had a POJO singleton class in one of those utility files, it worked, and all was well with the world:


EAR
|--- WAR
|--- EJB JAR
|--- Util 1 JAR
|--- Util 2 JAR
|--- etc.

Then I created a second WAR and found out (the hard way) that each WAR has its own ClassLoader, so each WAR sees a different singleton, and things break down from there. This is not so good.


EAR
|--- WAR 1
|--- WAR 2
|--- EJB JAR
|--- Util 1 JAR
|--- Util 2 JAR
|---

Related to : How do I write a J2EE/EJB Singleton?
How do I write a J2EE/EJB Singleton?
Programming Languages

A day ago my application was one EAR, containing one WAR, one EJB JAR, and a couple of utility JAR files. I had a POJO singleton class in one of those utility files, it worked, and all was well with the world:


EAR
|--- WAR
|--- EJB JAR
|--- Util 1 JAR
|--- Util 2 JAR
|--- etc.

Then I created a second WAR and found out (the hard way) that each WAR has its own ClassLoader, so each WAR sees a different singleton, and things break down from there. This is not so good.


EAR
|--- WAR 1
|--- WAR 2
|--- EJB JAR
|--- Util 1 JAR
|--- Util 2 JAR
|---
J2EE: Singleton vs keeping things in session
Programming Languages

When should an object (i.e. an application-wide properties file) be kept in the session, as opposed to creating a singleton to keep it? When should each of these approaches be used?


Note: I am working on a clustered environment, if that makes any difference.


In which real life senario for Java/j2ee application we are using singleton class
Programming Languages

Hello All,
Singleton class used by an application to ensure that at any time there is only one instance of a class created. You can achieve this by having the private constructor in the class and having a getter method which returns an object of the class and creates one for the first time if its null.
Please suggest me in which real life senario(With Small example) for Java/j2ee application we are using singleton class.
Thanks in advance.
Thanks and Regards,
Sumanta Panda
J2EE REST (Wink) - Can be REST Api class defines as singleton?
2/12/2014 3:40 pm Programming Languages

I am using J2EE with WASLiberty & Apache Wink (REST Impl). I would need in some cases to have api class to be singleton, however private constructor probably wont work with REST. Has anyone used api to be singleton ? any hints ?




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