Question reagarding beanName attribute of @EJB annotation

[Mohit G Gupta]

Source : Enterprise JavaBeans 3.1 O'Reilly Sixth Edition

Chapter 16: JNDI, the ENC, and Injection

@javax.ejb.EJB (Page:264)

The beanName()is the EJB name of the EJB referenced. It is equal to either the value you specify in the @Stateless.name()or @Stateful.name()annotation or the value you put in the <ejb-name>field in the XML deployment descriptor

Suppose MyEJB wants a reference to the local business interface of MyEJB2. Then, as per the above statement(The beanName()is the EJB name of the EJB referenced)
the beanName should be equal to "MyEJB2".
However,its also written that its value can be equal to "value you put in the <ejb-name>field in the XML deployment descriptor".
The value put in the <ejb-name> is the name of the EJB that wants a reference to some other bean.(Here,MyEJB)

Question 1:How can the 2 statements in BOLD be true.They seem to be contradictory ?

[Frits Walraven]

The examples in the OReilly book are not showing you the complete picture, it costed me also some time to figure it out, but here are the two adjusted examples:

@Stateless(name="MyEJB2") // this name is used in the beanname of the referring EJB
public class MySecondEJBBean implements MyEJB2LocalBusiness
{
   . . .
}

@Stateful(name="MyEJB")
@EJB(name="ejbs/referenceToMyEJB2", beanInterface=MyEJB2LocalBusiness.class, beanName="MyEJB2") // here is the reference
public class MyEJBBean implements MyEJBLocalBusiness
{
   . . .
}

or in xml
<ejb-jar> <enterprise-beans> <session> <ejb-name>MyEJB2</ejb-name> <!--this name is used in the beanname of the referring EJB --> </session> <session> <ejb-name>MyEJB</ejb-name> <ejb-local-ref> <ejb-ref-name>ejbs/referenceToMyEJB2</ejb-ref-name> <ejb-ref-type>Session</ejb-ref-type> <local>org.ejb3book.example.MyEJB2LocalBusiness</local> <ejb-link>MyEJB2</ejb-link> <!-- here is the reference --> </ejb-local-ref> </session> </enterprise-beans> </ejb-jar>
Regards,
Frits

[Mohit G Gupta]

Thanks Frits.

[gurpeet singh]

i couldnt understand the purpose of name attribute in @EJB annotation and the corresponding <ejb-ref-name> DD tag. can somebody please explain with an example >

[Frits Walraven]

name attribute in @EJB annotation and the corresponding <ejb-ref-name> DD tag

That name is to be used when you do a lookup inside the MyEJBBean class (it is actually a short name)
for example:

@Stateful(name="MyEJB")  
@EJB(name="ejbs/referenceToMyEJB2", beanInterface=MyEJB2LocalBusiness.class, beanName="MyEJB2") // here is the reference  
public class MyEJBBean implements MyEJBLocalBusiness  
{  
   @Resource SessionContext context;
     
   public String getEJB2message() {
      MyEJB2LocalBusiness  g = (MyEJB2LocalBusiness) context.lookup("ejbs/referenceToMyEJB2");
      // invoke method on EJB2
      String result = g.getMessage();
      return result;
   }
} 

Regards,
Frits

[gurpeet singh]

@EJB(name="ejbs/referenceToMyEJB2", beanInterface=MyEJB2LocalBusiness.class, beanName="MyEJB2") // here is the reference

so is it like that whatever name is specify in name attribute of @EJB annotation gets added to the java:comp/env namespace of the bean from which I am doing injection(in this case MyEjbBean) ? is it mandatory to specify beanName attribute always ? if there is just one session bean that implements whatever interface we give in beanInterface attribure, can I omit beanName ?

[Frits Walraven]

so is it like that whatever name is specify in name attribute of @EJB annotation gets added to the java:comp/env namespace of the bean from which I am doing injection(in this case MyEjbBean) ?

Correct.

is it mandatory to specify beanName attribute always ?

No

if there is just one session bean that implements whatever interface we give in beanInterface attribure, can I omit beanName ?

Exactly: you are getting the picture!

Just to confirm from the API:

javax.ejb Annotation Type EJB
Either the beanName or the lookup element can be used to resolve the EJB dependency to its target session bean component. It is an error to specify values for both beanName and lookup.

If no explicit linking information is provided and there is only one session bean within the same application that exposes the matching client view type, by default the EJB dependency resolves to that session bean.

Just have a look at the picture explaining the difference between beanName and lookup (My notes, chaper 7.2 @EJB - beanName vs lookup)

Regards,
Frits