问尝试使用Java API Client查看Google Drive上的更改时出现"401 Unauthorized“

EN

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;
}

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)