It would help if you could list the code snippets on how you create the URL and retrieve the token.
Here is an example of how we implemented very similar to what you are trying to do, perhaps this will help.
Define the service as shown below (snippet) and define the values (host, URL, etc.) in OSGI (or you can also program them for testing)
@Service(value = OauthAuthentication.class) @Component(immediate = true, label = "My Oauth Authentication", description = "My Oauth Authentication", policy = ConfigurationPolicy.REQUIRE, metatype = true) @Properties({ @Property(name = Constants.SERVICE_VENDOR, value = "ABC"), @Property(name = "service.oauth.host", value = "", label = "Oauth Host", description = "Oauth Athentication Server"), @Property(name = "service.oauth.url", value = "/service/oauth/token", label = "Oauth URL", description = "Oauth Authentication URL relative to the host"), @Property(name = "service.oauth.clientid", value = "", label = "Oauth Client ID", description = "Oauth client ID to use in the authentication procedure"), @Property(name = "service.oauth.clientsecret", value = "", label = "Oauth Client Secret", description = "Oauth client secret to use in the authentication procedure"), @Property(name = "service.oauth.granttype", value = "", label = "Oauth Grant Type", description = "Oauth grant type") }) public class OauthAuthentication { ... @Activate private void activate(ComponentContext context) { Dictionary<String, Object> properties = context.getProperties(); host = OsgiUtil.toString(properties, PROPERTY_SERVICE_OAUTH_HOST,new String()); // Similarly get all values url = clientID = clientSecret = grantType = authType = "Basic" + " "+ Base64.encode(new String(clientID + ":" + clientSecret)); } public static void getAuthorizationToken( try { UserManager userManager = resourceResolver.adaptTo(UserManager.class); Session session = resourceResolver.adaptTo(Session.class); // Getting the current user Authorizable auth = userManager.getAuthorizable(session.getUserID()); user = auth.getID(); password = ... ... ... String serviceURL = (host.startsWith("http") ? "": protocol + "://") + host + url; httpclient = HttpClients.custom().build(); HttpPost httppost = new HttpPost(serviceURL); // set params ArrayList<BasicNameValuePair> formparams = new ArrayList<BasicNameValuePair>(); formparams.add(new BasicNameValuePair("username", user)); formparams.add(new BasicNameValuePair("password", password)); formparams.add(new BasicNameValuePair("client_id", clientID)); formparams.add(new BasicNameValuePair("client_secret",clientSecret)); formparams.add(new BasicNameValuePair("grant_type",grantType)); UrlEncodedFormEntity postEntity = new UrlEncodedFormEntity(formparams, "UTF-8"); httppost.setEntity(postEntity); // set header httppost.addHeader("Authorization", authType); response = httpclient.execute(httppost); HttpEntity entity = response.getEntity(); if (response.getStatusLine().getStatusCode() == 200) { if (entity != null) { object = new JSONObject(EntityUtils.toString(entity)); } if (object != null) { accessToken = object.getString("access_token"); //// } } }