EJB Stateless Session Bean应该如何正确注入到web模块中？

Question

Being completely new to Java EE (but not to Java itself) I'm trying to build a very simple "Enterprise Application" with Hibernate as JPA provider and JSF as the actual UI framework. For this purposes I'm using the NetBeans 7 with GlassFish 3.1.

{ApplicationName}-ejb:

I've accomplished to generate entity classes from database and local sesssion beans for these entities. Beans.xml is in place.

@Stateless
public class QuestFacade extends AbstractFacade<Quest> implements QuestFacadeLocal {
    // some methods here as well as EntityManager injection ...
}

{ApplicationName}-war:

I've created a simple POJO as a backing bean for the JSF page. I've annotated it with javax.inject.@Named and javax.enterprise.context.@SessionScoped . This backing bean is now accessible from the JSF page as well as being injected when the actual page is accessed. Beans.xml is in place as well.

@Named
@SessionScoped
public class QuestBean implements Serializable {

    @EJB
    protected QuestFacade questFacade;

    // several methods delegating lookups to the questFacade ...
}

Having this deployed and page accessed, I'm, however, getting an error from GlassFish that the QuestFacade cannot be looked up by the JNDI.

The stacktrace is quite long but the initial cause could be enough:

Caused by: javax.naming.NamingException: Lookup failed for 'model.session.QuestFacade#model.session.QuestFacade' in SerialContext[myEnv={java.naming.factory.initial=com.sun.enterprise.naming.impl.SerialInitContextFactory, java.naming.factory.state=com.sun.corba.ee.impl.presentation.rmi.JNDIStateFactoryImpl, java.naming.factory.url.pkgs=com.sun.enterprise.naming} [Root exception is javax.naming.NameNotFoundException: model.session.QuestFacade#model.session.QuestFacade not found]
    at com.sun.enterprise.naming.impl.SerialContext.lookup(SerialContext.java:518)
    at com.sun.enterprise.naming.impl.SerialContext.lookup(SerialContext.java:455)
    at javax.naming.InitialContext.lookup(InitialContext.java:392)
    at javax.naming.InitialContext.lookup(InitialContext.java:392)
    at com.sun.ejb.EjbNamingReferenceManagerImpl.resolveEjbReference(EjbNamingReferenceManagerImpl.java:173)
    ... 74 more
Caused by: javax.naming.NameNotFoundException: model.session.QuestFacade#model.session.QuestFacade not found
    at com.sun.enterprise.naming.impl.TransientContext.doLookup(TransientContext.java:248)
    at com.sun.enterprise.naming.impl.TransientContext.lookup(TransientContext.java:215)
    at com.sun.enterprise.naming.impl.SerialContextProviderImpl.lookup(SerialContextProviderImpl.java:77)
    at com.sun.enterprise.naming.impl.LocalSerialContextProviderImpl.lookup(LocalSerialContextProviderImpl.java:119)
    at com.sun.enterprise.naming.impl.SerialContext.lookup(SerialContext.java:505)
    ... 78 more

I understand that I'm persuading GlassFish to inject an EJB from a different module within the same application. Should the @Remote interface be used instead? I've also tried to explicitely specify the name for both @Stateless and @EJB annotation but without any success.

I believe that I'm doing something fundamentaly wrong, but I cannot find out what.

Any suggestion or would be greatly appreciated!

Answer 1

I believe that I'm doing something fundamentaly wrong, but I cannot find out what.

What you're doing wrong is that if you implement a business interface (either @Local or @Remote ), then you must declare the variable where injection takes place as having the type of that interface, not of the actual bean class.

So in your case:

@Named
@SessionScoped
public class QuestBean implements Serializable {

    @EJB
    protected QuestFacadeLocal questFacade;

    // several methods delegating lookups to the questFacade ...
}

However, a business interface is not required in EJB when you're doing local (in-jvm) communication. As you discovered, if you don't specify a business interface at all for your EJB, you can inject the bean class itself. This is because you then automatically get the so-called no-interface view .

If you want, you can optionally declare that you want BOTH the local view and the no-interface view. In that way, you can inject your bean class in places whether either the bean type itself is declared or its business interface. For this you use the @LocalBean .

@Stateless
@LocalBean
public class QuestFacade extends AbstractFacade<Quest> implements QuestFacadeLocal {
    // some methods here as well as EntityManager injection ...
}

Injection can thus happen in two ways now:

@Named
@SessionScoped
public class QuestBean implements Serializable {

    @EJB
    protected QuestFacadeLocal questFacade; // possible because of local view
    @EJB
    protected QuestFacade questFacadeN; // possible because of no-interface view

    // several methods delegating lookups to the questFacade ...
}

In practice I didn't found much use for having both methods available at the same time though, but maybe this adds to your understanding.

Answer 2

Apparently the problem was that I generated @Local session beans. Per this tutorial it is no longer necessary (?) to specify the @Local or @Remote interface. I still not completely understand the problem though.

I Hope this answer could potentialy save up some time to somebody:-)

Jarda