"401 Unauthorized" when trying to watch changes on Google Drive with Java API Client

Question

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)

Answer 1

API returning an HTTP 401 or HTTP 403 response when calling the Drive API. These errors could indicate any of:

Token expiry, Token revocation, (This would cause both the access token and the refresh token to stop working), Token not authorized for needed scopes, Request not authorized correctly with OAuth 2.0 protocol.

Token expiry can be handled by calling refreshToken(). If that call fails with an "Invalid Credentials"