Angular post return 401. Oauth2

Ionic Framework ionic-v3
1

I want use oauth2 in my ionic app. but i get error:

Failed to load resource: the server responded with a status of 401 ()

Error: Http failure response for http://localhost:8080/oauth/token: 401 OK

Response:

{"timestamp":1502983544253,"status":401,"error":"Unauthorized","message":"Full authentication is required to access this resource","path":"/oauth/token"}

Angular function:

login(username, password) : Observable<any> {

 let params: HttpParams = new HttpParams();
 params.set('username', username);
 params.set('password', password);
 params.set('client_id', this.clientId);
 params.set('client_secret', this.clientSecret);
 params.set('grant_type', 'password');


 let headers = new HttpHeaders();
 headers.set('Content-Type', 'application/x-www-form-urlencoded');

 return this.http.post(this.EndPointUrl, {
   params:params
 }, { headers:headers}).map(this.handleData).
   catch(this.handleError);  }

I can get token using, PostMan and curl, CORS in my server is enabled for this endpoint so i think the auth server works properly.

Does anyone know what I’m doing wrong?