AngularJS/Spring MVC, HttpSession not persistent

We are developing a web application, we're using Spring MVC (along with Spring Boot and Spring Security) and AngularJS. Therefore, we have two distinct servers running for the application.

We are trying to store the user session backend, to ensure a proper level of security, so we tried to use the HttpSessionobject, but every time we want to retrieve the existing session, a new instance is created (we've checked the session ids).

Here's what we're doing to login :

$scope.authenticate = function () {

  var postObject = new Object();
  postObject.mail = $scope.userName;
  postObject.password = $scope.userPassword;

  $http({
    url: "http://localhost:8080/login",
    method: "POST",
    dataType: "json",
    data: postObject,
    headers: {
      "Content-Type": "application/json"
    }
  }).success(function successCallback(response, status) {
      if (status == 200) {
        $scope.messageAuth = "Login successful"
        $scope.go('/services');
      }
    })
    .error(function errorCallback(error, status) {
        $scope.messageAuth = "Error " + response;
    });
};

Then, we check the credentials, if they are correct, we store the user information into a new session :

@RestController
public class UserController {

@Resource
UserService userService;

@CrossOrigin
@RequestMapping(value = "/login", method = RequestMethod.POST, produces = "application/json")
public ResponseEntity<User> loginSubmit(@RequestBody User user, HttpServletRequest request, HttpSession session) {
    if (isAuthorized(user)) {
        User authenticatedUser = this.userService.getUserByMail(user.getMail());
        authenticatedUser.setPassword(null);

        session.invalidate();
        HttpSession newSession = request.getSession(true);
        newSession.setAttribute("USER_ROLE", authenticatedUser.getRole());

        System.out.println("/login : SESSION ID = " + newSession.getId());
        System.out.println("/login : " + newSession.getAttribute("USER_ROLE"));

        return ResponseEntity.ok(authenticatedUser);
    } else {
        return ResponseEntity.status(HttpStatus.UNAUTHORIZED)
                .body(null);
    }
}

@RequestMapping("/user")
public String user(Principal user, HttpServletRequest request, HttpSession session) {
    System.out.println("/user : SESSION ID = " + session.getId());
    System.out.println("/user : " + (String) request.getSession(false).getAttribute("USER_ROLE"));
    return (String) session.getAttribute("USER_ROLE");
}

And finally, from the Angular app, we'd like to get the user information by calling /user like this :

var f = function() {
    $http.get('http://localhost:8080/user').success(function successCallback(response) {
      console.log(response);
    }).error(function() {
      console.log('error');
    })
};

We've already tried pretty much every we found about how to manage a session with Spring Security, maybe the problem comes from the Angular part?

Any help would be greatly appreciated,

Thanks in advance