Singleton EJBs in Weblogic

Question

Hello everyone,
I'm developing an application (with Weblogic 11gR1PS1) which needs a single point of access to get tickets for making requests. The numbers are sequential and cannot be 2 tickets with the same number, so Concurrency is an issue. Based on this we came up with 2 ideas:
1- Creating a singleton EJB which will generate the tickets number to avoid 2 concurrent instances to generate the same number (if executing aproximately at the same time). Unfortunately I don't know how to do that with EJB 3.0 , I know that EJB 3.1 has a @Singleton annotation but that's not an option.
2- Try to limit up the instances of a the generator Stateless Bean to 1 , making it a singleton. Unfortunately I don't know how to limit the number of instances in a pool of a specific EJB to 1, which is what is needed.
I don't know which solution suits best, or even if there is a third one which any of you might know. Any suggestions will be appreciated!
Thank you

Answer 1

To limit the number of beans in the pool you can use the following:
- create a deployment plan
- create a file a deployment override weblogic-ejb-jar.xml and place this in the right directory (defined in the deployment plan)
- add to the deployment override the following:
<?xml version='1.0' encoding='UTF-8'?>
<weblogic-ejb-jar xmlns="http://www.bea.com/ns/weblogic/10.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.bea.com/ns/weblogic/10.0 http://www.bea.com/ns/weblogic/10.0/weblogic-ejb-jar.xsd">
<weblogic-enterprise-bean>
<ejb-name>NameOfYourEJB</ejb-name>
<stateless-session-descriptor>
<pool>
<max-beans-in-free-pool>1</max-beans-in-free-pool>
<initial-beans-in-free-pool>1</initial-beans-in-free-pool>
</pool>
</stateless-session-descriptor>
</weblogic-enterprise-bean>
Now there is only one bean in the pool. The problem with this is clients calling the EJB have to wait, until the EJB is released. This could have a negative effect on your response time of the application.
Maybe you can create a normal singleton, for example,
public class SomeSingleton {
private static final MyObject myObject;
private SomeSingletonl() {
static {
// create some instance of MyObject
public static MyObject getMyObject() {
return myObject;
Then you can call this from your EJB