EntityManager injection in a Message Driven Bean

[chrisouellette]

I am running an EJB3 Message Driven Bean and I would like to inject Application scoped seam components as well as an EntityManager instance but anything I inject with the @In annotation is coming in as null. I've scoured the boards to see if anyone is having a similar problem but I can't find anything.

My MDB class:

@Name("myMDB")
@MessageDriven(activationConfig = { 
                @ActivationConfigProperty(propertyName = "destinationName", propertyValue = "jms/myQueue"),
                @ActivationConfigProperty(propertyName = "destinationType", propertyValue = "javax.jms.Queue") })
public class MyMDB implements MessageListener {

    @Logger
    private Log log;
    
    @In
    EntityManager localEntityManager;
    
    @In
    private MyApplicationScopedComponent myAppComponent;

    public void onMessage(Message message) {
// Messages are being picked up but
// localEntityManager and myAppComponent are null
}
}

Am I missing something here? My understanding of Seam MDB's is that Application scoped components can be injected into MDB's. And what about EntityManager? I've tried using @PersistenceContext to get the EntityManager but that doesn't work either.

I've tried debugging and I don't have an ApplicationContext.

My environment:
Seam 2.1.2 (and I just tried Seam 2.2.0)
WebSphere 6.1

Any help would be appreciated. Thanks,

-Chris

[lvdberg]

Hi Chris,

I took me a while to get things working, but it works with me. Be aware that you must define the SEAM interceptor somewher. I do this in the ejb-jar.xml file (under META-INF).

It content should be:

<?xml version="1.0" encoding="UTF-8"?>
<ejb-jar xmlns="http://java.sun.com/xml/ns/javaee" 
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
         xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/ejb-jar_3_0.xsd"
         version="3.0">
   <interceptors>
      <interceptor>
         <interceptor-class>org.jboss.seam.ejb.SeamInterceptor</interceptor-class>
      </interceptor>
   </interceptors>
   <assembly-descriptor>
      <interceptor-binding>
         <ejb-name>*</ejb-name>
         <interceptor-class>org.jboss.seam.ejb.SeamInterceptor</interceptor-class>
      </interceptor-binding>
   </assembly-descriptor>
</ejb-jar>

Furthermore you must have your beans annotated with @Name as you already did and @JndiName (the latter can be done with a pattern in components.xml). I use it to send Seam events after receiving a Meeasge through JMS. Works great with Seam 2.1.2 and JBOSS 5.1

Leo

[chrisouellette]

Hi Leo,

Thanks for your reply. I do have the Seam Interceptors defined in my ejb-jar.xml and I am convinced that WebSphere is once again the cause of any problem. The good news is that I was able to get this working, albeit with a non-standard configuration. I had to make 2 concessions:

1. I had to use a stateless session bean instead of a POJO


2. I had to inject the bean using @EJB instead of @In

So now, my MDB code looks like this:

@Name("myMDB")
@MessageDriven(activationConfig = { 
                @ActivationConfigProperty(propertyName = "destinationName", propertyValue = "jms/myQueue"),
                @ActivationConfigProperty(propertyName = "destinationType", propertyValue = "javax.jms.Queue") })
public class MyMDB implements MessageListener {

    @Logger
    private Log log;
    
    @EJB
    private MyApplicationScopedSessionBean myAppComponent;

    public void onMessage(Message message) {
         myAppComponent.doStuff();
}
}

I'm actually OK with this setup. I can't use the EntityManager inside my MDB but I have full access to all Application scoped components, including EntityManager, in my session bean.

[dgomesbr]

Chris, like interceptors, u can't inject directly on mdb.

try

entityManager = (EntityManager) Component.getInstance("entityManager");

[chrisouellette]

Hi Diego,

Thanks for the response. I have tried using:

Component.getInstance("entityManager");

from inside the MDB, but I get an exception:

java.lang.IllegalStateException: No application context active

[kapitanpetko]

Why not just use the EJB PersitenceContext:

@PersistenceContext
EntityManager em;

The SPMC is not really useful in and MDB (since there is no conversation).