CDI Producer and Injection

Question

i want to use a producer in my application but i'm stuck at the point, where i'm trying to inject the bean. im getting the famous WELD-001409 error. please lighten up my understanding of cdi producer.

here's my interface:

@Named
    public interface MessageSender {
      void sendMessage();
    }

the bean:

public class EmailMessageSender implements MessageSender {

  @Override
  public void sendMessage() {
    System.out.println("Sending email message");
  }

}

and the producer:

@SessionScoped
public class MessageSenderFactory implements Serializable {

    private static final long serialVersionUID = 5269302440619391616L;

    @Produces
    public MessageSender getMessageSender() {
        return new EmailMessageSender();
    }

}

now i'm injecting the bean:

@Inject 
MessageSender messageSender;

when i'm trying to deploy the project i get the WELD-001409 error and eclipse also is saying that there are multiple injection points.

it works with explicit naming:

@Inject @Named("messageSender")
MessageSender messageSender;

is this naming neccessary?

Answer 1

1. Your EmailMessageSender class implements MessageSender and therefore it is a bean available for injection with type either EmailMessageSender or MessageSender .

2. Your producer returns a bean of type MessageSender .

3. Your injection point wants the only bean in the whole application whose type and qualifiers exactly match the type and qualifiers of the injection point .

From one and two you have 2 beans that match a single injection point - therefore that's an ambiguous dependency.

Bottom line, your producer is absolutely pointless (aside from causing the error) in the above example because it simply returns a new instance of EmailMessageSender which is the same exact effect as simply @Inject MessageSender since EmailMessageSender has the default scope @Dependent .