jakarta ee - Choose EJB to be injected without recompiling

Question

Imagine you have two implementations of a @Local interface

@Local
public interface LocalInterface {
}

@Stateless
public class MyFirstImplementation implements LocalInterface {
}

@Stateless
public class MySecondImplementation implements LocalInterface {
}

And I want to choose, without recompiling the project (that is, at runtime or using an external configuration property) which one (MyFirstImplementation or MySecondImplementation) I want to use.

public class MyClass {
   @EJB
   LocalInterface local;
}

Once one implementation is chosen, it does not have to change. I am using JBoss 5.1 if that helps.

Answer 1

You can achieve it using the deployment descriptor - ejb-jar.xml. Something like this (might not be 100% accurate, but I think you've got the point):

<ejb-jar> 
   <enterprise-beans>
      <session>
         <ejb-name>MyClass</ejb-name>
         <ejb-ref>
            <ejb-ref-name>ejb/myLocalReferencedBean</ejb-ref-name>
            <ejb-ref-type>Session</ejb-ref-type>
            <local>com.yourpackage.LocalInterface</local>
            <ejb-link>MyFirstImplementation</ejb-link>
            <injection-target>local</injection-target>
         </ejb-ref>
      </session>

      <session>
         <ejb-name>MyFirstImplementation</ejb-name>
         <!-- ... -->
      </session>
      <session>
         <ejb-name>MySecondImplementation</ejb-name>
         <!-- ... -->
      </session>
   </enterprise-beans>
</ejb-jar>

Another way is to use the CDI as described here: Inject @EJB bean based on conditions