GWT和Java EE SessionScoped bean未持久化

我正在玩w/EE,希望保持用户会话状态。我这里有会话bean:

@Stateful(mappedName = "UserSessionState")
@Named("UserSessionState")
@SessionScoped
@StatefulTimeout(value = 5, unit = TimeUnit.MINUTES)
public class UserSessionState implements Serializable
{
    private boolean hasPlayerId = false;
    private String playerId = "";

    public void setRandomPlayerId()
    {
        playerId = UUID.uuid();
        hasPlayerId = true;
    }

    public boolean hasPlayerId()
    {
        return hasPlayerId;
    }

    public String getPlayerId()
    {
        return playerId;
    }
}

这里是一个servlet(GameState是一个应用程序范围的bean,按预期工作,CustomExtendedHttpServlet只是HttpServlet的一个简单扩展)

public class NewUserJoined extends CustomExtendedHttpServlet
{
    @Inject
    protected GameState gameState;

    @Inject 
    protected UserSessionState user;

    @Override
    protected String doGetImpl(HttpServletRequest request, HttpServletResponse response, UserContext userLoginContext)
    {
        if (!user.hasPlayerId())
        {
            user.setRandomPlayerId();
        }        
        String userId = user.getPlayerId();

        if (!gameState.hasUser(userId))
        {
            gameState.addUser(userId, user);
            return "Hi, your ID is: " + user.getPlayerId() + ", there are " + gameState.getUserCount() + " other players here";
        }
        else
        {
            return user.getPlayerId() + " you're already in the game, there are: " + gameState.getUserCount() + " other players here";
        }
    }
}

我不确定发生了什么,但每当我从同一个HTTP会话调用新用户加入的servlet时,我在第一次调用时就会得到这个响应(如预期的那样):

“您好,您的ID是:,这里还有1位玩家”

在同一会话中重复相同的servlet调用会给我相同的消息: “您好,您的ID是:,这里还有两位玩家” ...

看起来用户会话状态的新实例正在一次又一次地创建。我做得对吗?

编辑1:这里是我用来发送请求的代码。看起来我在每个请求中都获得了一个新的会话ID,这是什么原因?

RequestCallback callback = new RequestCallback()
{
    @Override
    public void onResponseReceived(Request request, Response response)
    {
        log(response.getText());
    }

    @Override
    public void onError(Request request, Throwable exception)
    {
        log(
            "Response Error | "
            + "Exception: " + exception);
    }
};

RequestBuilder rb = new RequestBuilder(RequestBuilder.GET, SERVLET_URL);
rb.setCallback(callback);

try
{
    rb.send();
}
catch (RequestException e)
{
    log("Response Error | "
        + "Exception: " + e);
}