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Dependency injection through constructor does not work for EJB bean

My app is being deployed on to IBM WebSphere. I have a simple service and I'd like to know how dependency injection works in this case.
// stateless EJB
#Stateless
public class UserService {
private UserDAO userDAO;
// btw, UserDAO is stateless EJB as well
#Inject
public UserService(UserDAO userDAO) {
this.userDAO = userDAO;
}
// biz methods ...
}
It fails with the following error:
[ERROR ] CWWKZ0002E: An exception occurred while starting the
application my-app. The exception message was:
com.ibm.ws.container.service.state.StateChangeException:
com.ibm.ws.cdi.CDIException:
com.ibm.wsspi.injectionengine.InjectionException:
com.ibm.ejs.container.EJBConfigurationException: EJB class
com.demo.app.UserService must have a
public constructor that takes no parameters
I remember there was something in EJB spec that says: the class must have a public constructor that takes no parameters and it makes sense for me that the bean instance is first instantiated by the container and afterward dependency injection is done.
On the other hand, I've found this in WELD docs:
First, the container calls the bean constructor (the default
constructor or the one annotated #Inject), to obtain an instance of
the bean.
And I am confused a little bit, why my EJB cannot be instantiated.
How is the EJB instance being created and dependencies injected when we have constructor injection point?
Any ideas? :)

So what happens is that you do not meet the requirements for initializing EJB beans.
CDI spec has some limitations on constructors - either no-args or one with #Inject.
But there is also this chapter, which specifies that in EE, the set of rules is extended by what EJB session beans require.
And now we are getting into EJB spec which requires a no-arg constructor on a bean.
This should be in chapter Enterprise Bean Class where it states
The class must define a public constructor that takes no arguments.
Now, finally moving on to whether this should work - e.g. can you have an EJB bean using CDI constructor injection?
Well, let's have a look at CDI TCK, a set of tests that all implementation and containers have to pass in order to be able to claim they implement CDI.
There, we can see this bean and this test using it - so yea, this can work, but you need to have both constructors.

EJBs are registered as CDI beans. But first they have to meet the requirements of the EJB spec.
I guess it works just by providing the no-args constructor.

the creation of EJB session beans is done by EJB container but it can choose to use CDI to provide EE resource injection but EJB resolution is delegated to the container
https://docs.jboss.org/weld/reference/2.1.0.Final/en-US/html/ri-spi.html says:
Alternatively, the integrator may choose to use CDI to provide EE
resource injection. In this case, the EE_INJECT environment should be
used, and the integrator should implement the Section A.1.4, “EJB
services”, Section A.1.7, “Resource Services” and Section A.1.5, “JPA
services”.
....
Weld registers resource injection points with
EjbInjectionServices, JpaInjectionServices, ResourceInjectionServices
and JaxwsInjectionServices implementations upfront (at bootstrap).
This allows validation of resource injection points to be performed at
boot time rather than runtime
if you interested in how CDI and EJB are integrated. you can have a look at the code of weld-EJB module and weld-integration(glassfish code)

CDI and EJB mix with glassfish 3.1

I have two application deployed on glassfish - application A and B.
Both are deployed as war package, application B uses some components from application A.
Now in application A I have an interface:
public interface BusinessInterface() extends SomeOtherInterface {
void someAction();
}
I have 3 implementations of this interface - two in application A, one in application B: BusinessInterfaceA1, BusinessInterfaceA2, BusinessInterfaceB
As long as all of them are CDIBeans, everything is fine - I'm using custom #Qualifier annotations (#BusinessInterfaceA1, #BusinessInterfaceA2) and #Default annotation for B's implementation to distinguish them.
But now I need both application's A implementations to be Stateful EJBs and this is where it becomes funny.
When I just add #Statefull annotation on both implementations, a I got something like this:
javax.servlet.ServletException: org.jboss.weld.exceptions.WeldException: WELD-000049
details:
java.lang.IllegalStateException: Unable to convert ejbRef for ejb BusinessInterfaceA1 to a business object of type interface SomeOtherInterface
How can I fix it? I need all implementations to be avaliable in a way I could inject them like
#Inject #SomeAnnotation private BusinessInterface businessInterface;

It is bug in Glassfish 3.1. The workaround is, to mark implementation with all required interfaces, e.g.:
#Statefull/#Stateless
public class BusinessInterfaceImpl implements BusinessInterface, SomeOtherInterface {
// implementation
}
Even BusinessInterface extends SomeOtherInterface, and from Java specs its useless to do that, but as a workaround for that bug it works.
Another solution is to use Glassfish 4.0

JNDI lookup - Is it a correct way in my app?

I am writing an application in Java and I have some REST web services there. My application has following structure: http://cl.ly/L7Pv/o
REST web service classes are Stateless session beans. It works like charm. But Classes in red on the picture want to use that REST resources too.
As fas as I know I cannot use dependency injection and annotation #EJB there. I believe I have to use JNDI lookup. Documentation: http://docs.oracle.com/javaee/6/tutorial/doc/gipjf.html
But now I dont know how to write this JNDI lookup. I have tried these two:
context.lookup("java:global/diplomka/ListResource");
context.lookup("java:global/Diplomka_maven/ListResource");
What am I doing wrong? Is this a correct approach in the first place?
Thank you

If these classes (ListResource etc.) are Stateless session beans, you can put attribute name or mappedName in #Stateless annotation, e.g.:
#Stateless(mappedName="ejb/myRestService")
public class ListResource { ..
Once you have specified JNDI name of your stateless bean, it's easy to fetch the bean through JNDI lookup:
InitialContext ic = new InitialContext();
ListResource lr = (ListResource) ic.lookup("ejb/myRestService");
lr.doWhateverNeeded(..);

How to inject EJB Bean in different modul in Stripes ActionBean method?

Im writing JavaEE application, which contains of three modules.
In web module I need to inject ejb bean (in Stripes action bean method), which is located in ejb module.
So i followed this tutorial
http://www.stripesframework.org/display/stripes/Stripes+Injection+Enricher
My code goes like this>
#EJB
private CustomerServiceLocal customerService; //service layer for customer
and after deploying on GlassFish it returns following exception>
No EJB found in JNDI, tried the following names:
list of JNDI that it tried.
The bean is declared as follows>
#Stateless
#Local(value=CustomerServiceLocal.class)
#LocalBean
public class CustomerService implements CustomerServiceLocal {
interface>
#Local
public interface CustomerServiceLocal
I dont know what code could be relevant, so if I missed something just tell me what should I copied here.
So do you have any idea how to solve it ? How to set EJB Bean in different module in Stripes ActionBean method ?
It seems that stripes injection enricher is somehow wrongly configurated.
The problem is I need that service layer make work, since it is responsible for work with DB, and without it, I can just work with temporal local objects, which is useless.
Best regards,
OSiRiS

#Inject, #EJB, #Local, #Remote, #LocalBean, etc... : confused?

I have the following configuration:
1 EAR on one GF containing 2 EJB-JARs with EJB components.
1 WAR on another Glassfish server (=> other JVM) containing web components accessing the EJB components.
I have 2 EJB business services in each EJB-JAR of my EAR, and they are all developped like this:
#Remote
public interface ServiceAItf {
...
}
#Stateless
#Local
public class ServiceAImpl implements ServiceAItf {
...
}
In my WAR, I access the EJB components via an explicit "InitialContext.lookup" on the remote interface.
In my EAR, I am quite confused about the best practice for injection, in terms of performance, architecture, and so on...
I have the following questions:
As you can see, I have declared the annotation "#Local" on the service implementation without defining the local interface. Is it correct? At least I have no error at deployment. But maybe I should use the "#LocalBean" annotation instead? I suppose that the "#LocalBean" annotation simply allows to invoke the implementation directly as a "Local" EJB, but you have to use the implementation in your code like this:
#Stateless
#Local
public class ServiceBImpl implements ServiceBItf {
#EJB
private ServiceAImpl serviceA;
...
}
What is the best way to inject one EJB into another one?
It works like this:
#Stateless
#Local
public class ServiceBImpl implements ServiceBItf {
#EJB
private ServiceAItf serviceA;
...
}
But from what I noticed, the "serviceA" injected is the remote proxy, while it is in the same JVM within the same EAR file. So I suppose that there will be an impact on the performance. That's why I have tried to inject the service like this:
#Stateless
#Local
public class ServiceBImpl implements ServiceBItf {
#Inject
private ServiceAItf serviceA;
...
}
But it doesn't work in GF, I have the following exception:
WELD-001408 Unsatisfied dependencies for type [...] ...
I then tried to create a local interface, and the injection via the annotation "#Inject" works when both services
Even if I create a local interface like this, the service is not injected via the annotation "#Inject" but is null:
#Local
public interface ServiceALocalItf {
...
}
I read a lot of articles where it is highly recommended to use "#Inject" instead of "#EJB" when it is for a local invocation. That leads me to the following question: in which case the "#Local" EJB invocation is recommended (or simply used)?
After all this analysis, I come to the following conclusion:
For each service, I create a "#Local" and a "#Remote" interface.
From WAR to EJB-JAR of EAR, make a JNDI lookup to the remote interface.
From EJB-JAR to EJB-JAR, make an injection via "#EJB" to the local interface.
For two services within the same EJB-JAR, make an injection via "#Inject" to the local interface.
What do you think about it? Is it correct?

As you can see, I have declared the annotation "#Local" on the service
implementation without defining the local interface. Is it correct?
With EJB 3.1, the requirement for local interfaces was dropped. No need to write them unless you explicitly need them.
What is the best way to inject one EJB into another one?
Couple of things to write here:
With Java EE 6, Java Enterprise has changed. A new JSR defines a so-called managed bean (don't confuse with JSF managed beans) as a sort of minimum component that can still benefit from the container in terms of dependency injection and lifecycle management. This means: If you have a component and "just" want to use DI and let the container control its lifecycle, you do not need to use EJBs for it. You'll end up using EJBs if - and only if - you explicitly need EJB functionality like transaction handling, pooling, passivation and clustering.
This makes the answer to your question come in three parts:
Use #Inject over #EJB, the concept of CDI (a) works for all managed
beans (this includes EJBs) and (b) is stateful and therefore far
superior over pure #EJB DI
Are you sure that you need EJBs for your
components?
It's definitely worthwhile to have a look at the CDI
documentation

#Inject annotation is used for java beans(POJOs) while #EJB annotation is used for enterprise java beans. When a container inject an ejb provided by #EJB annotation to another bean it also controls that ejb's lifecycle, performs pooling for stateless beans and so on(when bean which is going to be injected is not deployed the reference will be null). If you use #Inject annotation CDI mechanism simply find and create an instance of injected resource like with new operator(if the implementation of interface which is going to be injected doesn't exist the reference will be null). You can use qualifiers with #Inject annotation to choose different implementation of injected interface.