CDI General Question

[aarnold]

I am working through the JBOSS A7 Quickstart examples and I have a basic question....  first let me give the code:

//Login.java

import java.io.Serializable;

import javax.enterprise.context.SessionScoped;
import javax.enterprise.inject.Produces;
import javax.faces.application.FacesMessage;
import javax.faces.context.FacesContext;
import javax.inject.Inject;
import javax.inject.Named;

@SessionScoped
@Named
public class Login implements Serializable {

   private static final long serialVersionUID = 7965455427888195913L;

   @Inject
   private Credentials credentials;

   @Inject
   private UserManager userManager;

   private User currentUser;

   public void login() throws Exception {
      User user = userManager.findUser(credentials.getUsername(), credentials.getPassword());
      if (user != null) {
         this.currentUser = user;
         FacesContext.getCurrentInstance().addMessage(null, new FacesMessage("Welcome, " + currentUser.getName()));
      }
   }

   public void logout() {
      FacesContext.getCurrentInstance().addMessage(null, new FacesMessage("Goodbye, " + currentUser.getName()));
      currentUser = null;
   }

   public boolean isLoggedIn() {
      return currentUser != null;
   }

   @Produces
   @LoggedIn
   public User getCurrentUser() {
      return currentUser;
   }

}

Why is @LoggindIn a Qualifier interface?  Why not use a class like Credentials earlier in the code?  What's the point of using @Produces?  Why not just @Inject some class?

Thanks,

Drew

[lightguard]

There may be other Users such as one which has not logged in, this further qualifies which instance you want to inject.

The @Produces creates the @LoggedIn User so you can @Inject it.

[aarnold]

Jason,

Thanks for the response!  I think I get what you are saying, but I still am a little shakey on the concept of injection in general I guess.  So the @Produces creates the @LoggedIn User so you can @Inject it.  I guess now I have a more fundemental question... Why inject?  Isn't injecting simply invoking the getCurrentUser() method on the instantiation of the Login class?  Why can't this be done with some call in a constructor?  Or even using @PostConstruct? Is this all needed because beans can not have parameterized constructors?

Thanks for you time.

--Drew

[aarnold]

Ok, hold on... I think I need to re-phrase.  Fields/Methods with @Inject get invoked on instation of the class.  I guess @Produces is for a user of the class?  Who can use this implemetation of @LoggedIn?  What if another class has a different @Produces @LoggedIn implementation?

[aarnold]

Jason,

I realize the previous questions reeked of ignorance.  I am in the process of digging into CDI for the first time.  I am reading the Weld - JSR-299 Reference Implementation now.  I didn't realize there was good literature out there on this topic.... http://docs.jboss.org/weld/reference/latest/en-US/html/index.html.

I'm sure the guide will clear things up for me.

Thanks so much for your response.

--Drew