Really stuck here. The code, built from examples provided by Google:
public static void main(String[] args) { try { HttpTransport httpTransport = new NetHttpTransport(); JsonFactory jsonFactory = new JacksonFactory(); GoogleAuthorizationCodeFlow flow = new GoogleAuthorizationCodeFlow.Builder( httpTransport, jsonFactory, CLIENT_ID, CLIENT_SECRET, Arrays.asList(DriveScopes.DRIVE)) .setAccessType("online") .setApprovalPrompt("auto") .build(); String url = flow.newAuthorizationUrl().setRedirectUri(REDIRECT_URI).build(); System.out.println("Please open the following URL in your browser then type the authorization code:"); System.out.println(" " + url); BufferedReader br = new BufferedReader(new InputStreamReader(System.in)); String code = br.readLine(); GoogleTokenResponse response = flow.newTokenRequest(code).setRedirectUri(REDIRECT_URI).execute(); GoogleCredential credential = new GoogleCredential().setFromTokenResponse(response); //Create a new authorized API client Drive service = new Drive.Builder(httpTransport, jsonFactory, credential).setApplicationName("Google Push").build(); //Insert a file File body = new File(); body.setTitle("My document"); body.setDescription("A test document"); body.setMimeType("text/plain"); java.io.File fileContent = new java.io.File("document.txt"); BufferedWriter bw = new BufferedWriter(new FileWriter(fileContent)); bw.write("allo!!!!"); bw.close(); System.out.println("file created? -> " + fileContent.createNewFile()); FileContent mediaContent = new FileContent("text/plain", fileContent); File file = service.files().insert(body, mediaContent).execute(); System.out.println("File ID: " + file.getId()); watchChange(service, "channelId", "web_hook", "https://clementlevallois.net/notifications"); // line 78 } catch (IOException ex) { Logger.getLogger(DriveCommandLine.class.getName()).log(Level.SEVERE, null, ex); } } private static Channel watchChange(Drive service, String channelId, String channelType, String channelAddress) { Channel channel = new Channel(); channel.setId(channelId); channel.setType(channelType); channel.setAddress(channelAddress); try { return service.changes().watch(channel).execute(); //line 91 } catch (IOException e) { e.printStackTrace(); } return null; } The stack trace:
com.google.api.client.googleapis.json.GoogleJsonResponseException: 401 Unauthorized at com.google.api.client.googleapis.json.GoogleJsonResponseException.from(GoogleJsonResponseException.java:145) at com.google.api.client.googleapis.services.json.AbstractGoogleJsonClientRequest.newExceptionOnError(AbstractGoogleJsonClientRequest.java:113) at com.google.api.client.googleapis.services.json.AbstractGoogleJsonClientRequest.newExceptionOnError(AbstractGoogleJsonClientRequest.java:40) at com.google.api.client.googleapis.services.AbstractGoogleClientRequest$1.interceptResponse(AbstractGoogleClientRequest.java:312) at com.google.api.client.http.HttpRequest.execute(HttpRequest.java:1049) at com.google.api.client.googleapis.services.AbstractGoogleClientRequest.executeUnparsed(AbstractGoogleClientRequest.java:410) at com.google.api.client.googleapis.services.AbstractGoogleClientRequest.executeUnparsed(AbstractGoogleClientRequest.java:343) at com.google.api.client.googleapis.services.AbstractGoogleClientRequest.execute(AbstractGoogleClientRequest.java:460) at Controller.DriveCommandLine.watchChange(DriveCommandLine.java:91) at Controller.DriveCommandLine.main(DriveCommandLine.java:78) 
