JAX-RS and CDI - Injecting stateful session bean : setter does not work

Question

I am working on a webservice using RESTEasy.

I have an "authentication" webservice with two methods : "login" and "logout".

I have a stateful session scoped bean, UserData with two attributes : "loggedIn", boolean, and "userId", Integer.

I am injecting UserData in my Authentication class. It is working well for the "loggedIn" attribute, when I call "login" method, it is set to true and then it remains true until the session ends.

But strangely it is not working with "userId" attribute. When I call "login" method, I set userId to my user id but right after the "setUserId" method is called, userId is still null.

Here is Authentication class code (without logOut method, unused for now ) :

package com.bini.dev.dilemme.web.api;

import javax.inject.Inject;
import javax.ws.rs.GET;
import javax.ws.rs.Path;
import javax.ws.rs.Produces;
import javax.ws.rs.QueryParam;

import com.bini.dev.dilemme.business.service.UserService;
import com.bini.dev.dilemme.persistence.model.User;
import com.bini.dev.dilemme.web.UserData;

@Path("/auth")
public class AuthenticationApi {

    @Inject
    private UserData userData;

    @Inject
    private UserService userService;

    @GET
    @Path("login")
    @Produces("application/json")
    public UserData logIn(@QueryParam("mail") String userMail, @QueryParam("password") String userHashedPassword) {
        try {
            this.logOut();
            User user = userService.getUserByMailAddress(userMail.trim());
            if (user == null)
                throw new Exception("User does not exists");
            boolean loggedIn = userService.checkUserPassword(user, userHashedPassword.trim());
            if (loggedIn) {
                userData.setLoggedIn(true);
                userData.setUserId(user.getUserId());
            }
            return userData;
        } catch (Exception e) {
            e.printStackTrace();
            return userData;
        }
    }
}

And here is the code of "UserData" class :

package com.bini.dev.dilemme.web;

import java.io.Serializable;

import javax.enterprise.context.SessionScoped;

import com.fasterxml.jackson.annotation.JsonAutoDetect;

@SessionScoped
@JsonAutoDetect(fieldVisibility = JsonAutoDetect.Visibility.PROTECTED_AND_PUBLIC, 
                getterVisibility = JsonAutoDetect.Visibility.NONE, 
                setterVisibility = JsonAutoDetect.Visibility.NONE)
public class UserData implements Serializable {

    protected Boolean loggedIn;

    protected Integer userId;

    public UserData() {
        this.loggedIn = false;
        this.userId = null;
    }
    public Boolean isLoggedIn() {
        return loggedIn;
    }

    public void setLoggedIn(Boolean loggedIn) {
        this.loggedIn = loggedIn;
    }
    public Integer getUserId() {
        return userId;
    }
    public void setUserId(Integer userId) {
        this.userId = userId;
    }

}

I tried with or without "Stateful" and "Stateless" annotation. Doesn't change anything.

I really have not idea what to do.

I thought it might be a "setter" syntax error, but I really don't see where.

EDIT : BTW, I am using Weld and RestEASY with WildFly server. Thanks :)