Dozer DozerBeanMapper Instantiation Startup EJB App Server Glassfish - glassfish

Question

Dozer's documentation states that you should only have one instance of DozerBeanMapper running in the app on the server. For initial development I ignored this, now I want to update the app to do this.
How can I instantiate the DozerBeanMapper class when the application starts on glassfish, and how would I access its "map" method in another class once the application has started or been newly deployed?
This is for EJBs so I can't use any servlet to do this.
OK, so I've finally had time to refactor this code. With the pointer from #Mikko Maunu, I am editing my question to provide the code that I have working for me for anyone who might find it useful in the future.
package com.xyz.utilities.singleton;
import javax.annotation.PostConstruct;
import javax.ejb.Singleton;
import javax.ejb.Startup;
import org.dozer.DozerBeanMapper;
#Startup
#Singleton
public class DozerInstantiator {
private DozerBeanMapper mapper = null;
#PostConstruct
void init() {
mapper = new DozerBeanMapper();
}
public DozerBeanMapper getMapper() {
return mapper;
}
}
And here is a straight forward usecase:
Inject an EJB member variable to your client class:
#EJB
DozerInstantiator di;
Within a method somewhere in the client class you can invoke the dozer mapper like so:
Credentials credentials = di.getMapper().map(credentialsDTO, Credentials.class);
// or
Credentials credentials = new Credentials();
di.getMapper().map(credentialsDTO, credentials);
If this is wrong or off base, someone please leave a comment. Until then, this seems to work so I'll use this solution I've developed with Mikko's input.

Answer 1

If you are using GlassFish 3.x, then you can use EJB 3.1 Singleton Session Bean:
#Startup //initialization in application startup
#Singleton //only one instance
public class DozerInitializer {
private String status;
#PostConstruct //executed once and only once when sole instance is created
void init {
//do steps needed to instantiate DozerBeanMapper
//here
}
}