HTPPSession with the Google Cloud Ends Endpoint every time

Question

I have been using Google Cloud Endpoints successfully. Now for custom auth, I want to use HTTPSession. The problem is that the initial session is not reused in future calls, and a new session is created (I see that from the data warehouse administrator the whole session exists, object _AH_SESSION). As stated in the docs, I included it in appengine-web.xml:

<sessions-enabled>true</sessions-enabled>

I made some code examples to narrow it down:

@Api(name = "loginService", version = "v0.1.5")
public class LoginService {

private static final Logger log = Logger.getLogger(LoginService.class.getName());

@ApiMethod(name = "login", path= "login")
public LoginResponse login(HttpServletRequest req)
{
    HttpSession session = req.getSession(false);
    if(session == null){
        log.warning("creating new session");
        session = req.getSession(true);
    }

    LoginResponse resp = new LoginResponse();
    resp.statusCode = 200;
    resp.statusMessage = "SessionId:" + session.getId();

    return resp;
}


@ApiMethod(name = "show", path= "show")
public LoginResponse show(HttpServletRequest req)
{
    //session should exist when calling LOGIN first
    HttpSession session = req.getSession(false); //NULLPOINTER since session from login is not being reused/found!
    LoginResponse resp = new LoginResponse();
    resp.statusCode = 200;
    resp.statusMessage = "SessionId:" + session.getId();
    return resp;
}

public class LoginResponse implements Serializable{
    public int statusCode;
    public String statusMessage;
}

} `

, , . ( Postman - ) Chrome, API) "show", , , nullpointer.

mikO , . ? . "" appengine, Postman .. (, , , ), , , , . :

public class LoginServlet extends HttpServlet {

    private static final Logger log = Logger.getLogger(LoginServlet.class.getName());

    public void doGet(HttpServletRequest request,
                      HttpServletResponse response)
            throws ServletException, IOException {
        HttpSession s = request.getSession(false);
        if (s == null) {
            log.warning("creating new session");
            s = request.getSession(true);
        }

        response.setContentType("text/html");

        PrintWriter out = response.getWriter();
        out.println("<h1>" + s.getId() + "</h1>");
    }
}

!