How to fill #EJB annotated fields programmatically via glassfish container? - servlets

Question

I have a following problem. I have defined an interface:
#Local
public interface ProductTypeLister {
Collection<ListElement> getList();
}
Also, I have defined an implementation for this thing:
#Stateless(name = "ProductTypeLister")
#Local(ProductTypeLister.class)
public class ProductTypeListerImpl implements ProductTypeLister {
#Override
public Collection<ListElement> getList() {
// Implementation code
}
}
And now I want to use it via annotation:
public class ListProductTypeAction extends ActionHandler {
#EJB
protected ProductTypeLister lister;
#Override
public String execute(HttpServletRequest request) throws ServletException {
request.setAttribute("list", lister.getList());
return "listPage.jsp";
}
}
But I get the NullPointerException, since lister is not filled. Now, the problem is, that ActionHandler is not a derivative of HttpServlet and is not executed by the container itself. Instead, we are using FrontController patter - i.e. there is one servlet that handles all the incoming messages and creates required handlers via a simple construction. And therefore the EJB annotated fields are not filled automatically. However, I can fill this specific case in the following manner:
public ListProductTypeAction() throws NamingException {
InitialContext context = new InitialContext();
lister = (ProductTypeLister) context.lookup("<PATH>/ProductTypeLister");
}
In that case everything works fine, but this means I have to do for every handler the specified lookup with JNDI help, but all I want is to get it with annotation help. Therefore, the main servlet needs the following method:
private void fillHandler(ActionHandler handler) {
// Fill #EJB annotated fields
}
But how can I fill it? Of course, I can manually run through every field and check if it's annotated EJB and fill it using JNDI based on the interface unqualified name. But is there a way to do this using the libraries I already have? After all, Glassfish is supposed to fill those fields during the deployment phase. How can I make him do that for a non-servlet class?

Answer 1

J2EE tutorial
Dependency injection is the simplest way of obtaining an enterprise bean reference. Clients that run within a Java EE server-managed environment,
JavaServer Faces web applications, JAX-RS web services, other
enterprise beans, or Java EE application clients, support dependency
injection using the javax.ejb.EJB annotation.
Applications that run outside a Java EE server-managed environment,
such as Java SE applications, must perform an explicit lookup. JNDI
supports a global syntax for identifying Java EE components to
simplify this explicit lookup.
So even if your class is inside a J2EE container, but its lifecycle is not managed by container, you are out of luck, you have to do it manually.